Citation
Sustainable design of pervious concrete pavements

Material Information

Title:
Sustainable design of pervious concrete pavements
Creator:
Hager, Angela Susan
Publication Date:
Language:
English
Physical Description:
xviii, 381 leaves : illustrations ; 28 cm

Subjects

Subjects / Keywords:
Lightweight concrete ( lcsh )
Pavements, Concrete -- Design and construction ( lcsh )
Sustainable design ( lcsh )
Lightweight concrete ( fast )
Pavements, Concrete -- Design and construction ( fast )
Sustainable design ( fast )
Genre:
bibliography ( marcgt )
theses ( marcgt )
non-fiction ( marcgt )

Notes

Bibliography:
Includes bibliographical references (leaves 375-381).
General Note:
Department of Civil Engineering
Statement of Responsibility:
by Angela Susan Hager.

Record Information

Source Institution:
|University of Colorado Denver
Holding Location:
Auraria Library
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
435528342 ( OCLC )
ocn435528342
Classification:
LD1193.E53 2009d H33 ( lcc )

Full Text
SUSTAINABLE DESIGN OF
PERVIOUS CONCRETE PAVEMENTS
by
Angela Susan Hager
B.S., Colorado School of Mines, 2003
M.S., University of Colorado Denver, 2005
A dissertation submitted to the
University of Colorado Denver
in partial fulfillment
of the requirements for the degree of
Doctor of Philosophy
Civil Engineering
2009


2009 by Angela S. Hager
All rights reserved.


This dissertation for the Doctor of Philosophy
degree by
Angela S. Hager
has been approved
by
Anil Ramaswami
Ross B. Corotis

Date


Hager, Angela S. (Doctor of Philosophy, Civil Engineering)
Sustainable Design of Pervious Concrete Pavements
Thesis directed by Professor Kevin L. Rens
ABSTRACT
This research evaluated the performance of a waste-incorporated pervious
concrete pavement (PCP) system in Denver, Colorado. This dissertation provides
recommendations for designing and constructing PCP in the unique Colorado environment
of fluctuating temperatures, low humidity, and frequent freeze/thaw conditions.
A PCP system functions both as a stormwater detention system and as a
pavement surface and must therefore meet specific hydrological and structural
performance criteria. Preliminary laboratory testing evaluated the spectrum of mixture
design recommendations and established a base mixture design to exceed these
performance criteria. Subsequent phases of laboratory testing modified this base mixture
design with fly ash, fine aggregate, and air-entraining admixture to establish acceptable
limits for each. Some mixtures exhibited a distinct region of imperviousness. The use of
hydration stabilizing admixture prevented this phenomenon and was therefore
recommended.
A PCP test section was constructed on the Auraria Campus of the University of
Colorado Denver. This test section was completed in a parking lot and utilized 20% fly ash
replacement for cement in the PCP mixture, crushed recycled concrete as the underlying
coarse aggregate, and 10% replacement of sand with crushed glass in the fine aggregate
layer. Testing of the PCP test section confirmed that the structural and hydrological
requirements were met.


Subsequent field investigations included monitoring of the PCP test section for
reduction in the heat-island effect, water quality, deterioration, clogging, and permeability.
The water quality analysis demonstrated that the waste-incorporated PCP system was
effective in filtering heavy metals and chlorides; however, it produced an alkalinic solution.
An examination of the suspected causes of PCP deterioration prompted an
investigation into the effect of deicing agents. Results demonstrated that deicers strip the
important cement binding paste from aggregate particles and thus contribute to the
accelerated deterioration of PCP. The remainder of the suspected failure mechanisms
were evaluated within the aforementioned phases of laboratory and field testing.
This research confirmed that sustainable PCP can be placed in the semi-arid
climate of Denver. Correct construction details were critical to the performance of the
pavement. Specific mixture design, placement, and curing recommendations resulted from
this research.
This abstract accurately represents the content of the candidates thesis^J recommend its
publication.
Signed
Kevin L. Rens


DEDICATION
I dedicate my dissertation work to my daughter, Mary Anna Hager. Mary, you have
given me the inspiration and motivation to fulfill my educational goals. I love you.
When I was a child, I had a poster which I kept for a number of years. This poster
showed a picture of a child, about 10 years old, sitting in front of a soccer goal looking onto
the field. The picture was taken from behind the goal such that you saw the back and side
of the child through the netting of the goal. Despite not being able to see the childs face,
he appeared to be lost in deep thought. Beneath the picture was the caption, If you can
dream it, you can become it. As a young child, I held on to the poster because I enjoyed
playing soccer and because the border was orange, my favorite color. I distinctly
remember one day contemplating this quote from William A Ward. If you can dream it, you
can become it. The message did not imply that your dreams, whatever they might be,
would be handed over to you or easily acquired. Quite to the contrary, I interpreted this
quote as stating that while your dreams are achievable, you must work constantly and
feverishly towards achieving them. You will inevitably experience set-backs or road-blocks
along the way, but if you truly desire to achieve your dream you must find a way to
overcome these obstacles. Your dream must be a paramount focus in your life. Each day
you must work towards achieving your goal. If you are willing to put this effort and
dedication towards your dream, then and only then, are you truly capable of achieving your
dream.
From then on I displayed this poster in my bedroom as a source of encouragement
and motivation. I even recall having affixed the poster to the ceiling directly above my bed


so as to reflect on my dreams each night before falling asleep. I held on to this poster for
many years, throughout high school and even in college. While it is no longer displayed in
my home, I try to embody this message in my daily life. If you have a dream, if it is
important to you, make it paramount in your life and work towards achieving it each and
every day.
Throughout my dissertation work, I encountered a number of obstacles and a
number of set-backs. I remember countless occasions when I felt that this work would
never end. Nonetheless, I continued to work towards my goal each day, and indeed,
eventually my goal came to fruition.
Mary, my daughter, this is the message that I want to pass on to you. I want you to
know that if you can dream it, you can become it. Never give up on your dreams. Believe
in yourself and believe in your dreams and youll be what you dream you can be. I will
always love you and I will always support you.


ACKNOWLEDGMENT
This project was a collaboration in the truest sense, and would not exist without the
support and input of more people than I can name. I would like to thank the following
people who played important roles in the process:
Dr. Kevin Rens, my thesis advisor, for his unrelenting support and
encouragement. I am fortunate to have come to know him and consider it
a work of providence that I found him as my advisor and friend. His
extensive knowledge of inspection and condition assessment of
infrastructure, and of cement and concrete properties were of considerable
benefit to this research.
Dr. Stephan Durham, for sharing his wit and wisdom, not just this year, but
throughout our shared time at UCD. His guiding voice has been ever-
present, and the impact he has had will follow me for years to come. His
tremendous knowledge of cement and concrete properties was of great
value throughout this research.
Dr. Anu Ramaswami, for imparting on me a fraction of her knowledge of
sustainability and environmental engineering. Her persistence and
determination are extraordinary and inspirational.
Dr. James Guo, for his expertise in stormwater management and Best
Management Practices.
Dr. Ross Corotis, for his extensive knowledge of life-cycle analysis and
structural system reliability.


Dr. Yunping Xi, for his valuable experience and knowledge of materials
science and waste-stream material reuse.
Additionally, I would like to thank those who offered significant contributions of
material, equipment, time and/or expertise to this project:
Bestway Concrete, for the generous donation of the pervious concrete
placed in the field application portion of this research. In particular, I would
like to thank Dan Bentz for sharing his knowledge of pervious concrete,
and assisting in the placement. I would also like to thank Marsha
Mendenhall for her assistance and support of the project.
Total Concrete Services, for supplying the tools and equipment to place
the pervious concrete in the field application. Particular thanks to Tracy
Nissen and Kyle Nissen for assisting in the placement of the pervious
concrete.
Rocky Mountain Bottling Company, mainly Tony Able, for donating the
crushed glass used in the pervious concrete test section.
Colorado Ready Mixed Concrete Association, for hosting the NRMCA
Pervious Concrete Contractor Certification course. Particular thanks to Joe
Rottman, for instructing the course, and for his guidance and assistance.
Oxford Recycling, particularly John F. Kent, for providing insight into the
use of waste-stream materials into the urban infrastructure and for
providing the recycled concrete for this project.
W.R. Grace, in particular Bill Hart, for donating the air-entraining admixture
used for the laboratory testing portion of this research.


Ken MacKenzie of the Urban Drainage and Flood Control District and Ben
Urbonas of Urban Water Research Institute for providing insight and
guidance into stormwater best management practices.
Auraria Higher Education Center for providing a home for the field portion
of this project. Particular thanks to Jill Jennings, Jim Fraser, Doug
McLean, and David Kraijileck.
The students who participated in the NRMCA training course and assisted
in the installation of the pervious concrete: Robert (Bobby) Cavaliero, Xin
Jiang, Ronnie Kurzdorfer, Jesus (Dan) Martinez, Ramon Martinez, Scott
Meredith, Adam Reed, Michael Sheperd, Brian Staley, Rachelle Urso,
Erika Vega, Darren Weldon, Bo Yan, Ryan Marmet, Veronica Hogg-
Cornejo, Varun Natraj, and Hiep Nguyen. You have left a lasting
monument with the University and with me.
The students who assisted in the laboratory phases of this research: Rui
Liu, Xin Jiang, Dehui (Joelle) Zhou, Ramon Martinez, and Andrea Solis.
City and County of Denver for supporting this research both directly and
indirectly. Particular thanks to Pat Kennedy for his creativity in expanding
the scope of the deicer testing, and for assisting in this phase of the
research.
My family, for their love, support, and endless hours of assistance. I
cannot thank you enough for all you have done for me in the last few
years. You provided me with the strength, motivation, and ability to
continue my academic pursuits through many hardships. Special thanks to
those members of my family who assisted during the multiple phases of
this research. I could not have done this without you.


TABLE OF CONTENTS
Figures....................................................................xv
Tables.....................................................................xviii
Chapter
1. Introduction and Scope.......................................................1
1.1 Research Objectives..........................................................4
2. Stormwater Best Management Practices.........................................8
2.1 The Adverse Impacts of Urban Development....................................10
2.2 Urban Drainage and Flood Control District...................................12
3. Literature Review...........................................................13
3.1 Recommendations and Applications............................................16
3.1.1 Urban Drainage and Flood Control District Recommendations...................17
3.1.2 Portland Cement Association Recommendations.................................19
3.1.3 National Ready Mixed Concrete Association Recommendations...................20
3.1.4 American Concrete Institute Recommendations.................................21
3.2 Pervious Concrete Materials.................................................21
3.3 Pervious Concrete Mixture Proportions.......................................26
3.4 Waste-Stream Material Options for Pervious Concrete Pavement System.........29
3.4.1 Fly Ash Replacement for Cement..............................................31
3.4.2 Recycled Concrete Replacement for Concrete Aggregate........................33
3.4.3 Recycled Concrete Replacement for Aggregate Base Layer......................34
3.4.4 Rubber Replacement for Concrete Aggregate...................................35
3.4.5 Rubber Replacement for Aggregate Base Layer.................................36
3.4.6 Crushed Glass Replacement for Sand..........................................36
3.4.7 Waste-Stream Material Leaching (Kocman 2008)................................38
3.5 Pervious Concrete Admixtures................................................41
3.5.1 Air-Entraining Admixture (AEA)..............................................41
3.5.2 Viscosity Modifying Admixture (VMA).........................................42
3.5.3 Set Retarders...............................................................42
3.6 Pervious Concrete Cleaning and Maintenance..................................43
4. Background: Pervious Concrete Pavement in Denver, Colorado..................44
4.1 Colorado Hardscapes (2004)..................................................44
4.2 Safeway Grocery Store (2005)................................................48
4.3 City of Lakewood Maintenance Facility (2005)................................50
4.4 Wal-Mart Super Center (2006)................................................54
4.5 Bestway Concrete (2006).....................................................57
4.6 Vitamin Cottage (2007)......................................................59
4.7 Auraria Campus of the University of Colorado at Denver Parking Lot K (2008).62
4.8 UDFCD Moratorium............................................................64
4.9 CTL Thompson Materials Investigation........................................65
5. Laboratory Testing of Pervious Concrete Pavement............................67
5.1 Laboratory Testing Methodology..............................................69
XI


5.1.1 Cylinder Compression Testing Methodology..................................69
5.1.2 Core Compression Testing Methodology......................................71
5.1.3 Porosity Testing Methodology..............................................73
5.1.4 Freeze-Thaw Testing Methodology...........................................75
5.2 Laboratory Testing Phase I................................................80
5.2.1 Placement and Curing Procedures...........................................81
5.2.2 Testing Results...........................................................82
5.2.3 Lessons Learned...........................................................86
5.3 Laboratory Testing Phase II...............................................87
5.3.1 Testing Results...........................................................89
5.3.2 Lessons Learned...........................................................90
5.4 Laboratory Testing Phase III (Mini-Mixtures)..............................91
5.4.1 Testing Results and Discussion............................................92
5.5 Laboratory Testing Phase IV and Phase V (AEA and Fly Ash).................94
5.5.1 28-Day Compressive Strength Testing.......................................95
5.5.2 28-Day Porosity Testing...................................................97
5.5.3 56-Day Compressive Strength Testing.......................................99
5.5.4 56-Day Porosity Testing..................................................101
5.5.5 Freeze-Thaw Testing......................................................103
5.5.6 A Note on Timing.........................................................108
5.5.7 Commentary and Conclusions...............................................109
5.5.7.1 Error Bars............................................................109
5.5.7.2 The Impervious Zone...................................................109
5.5.7.3 Conclusions...........................................................111
5.6 Laboratory Testing Phase VI (Fine Aggregate).............................113
5.6.1 28-Day Compressive Strength Testing......................................115
5.6.2 28-Day Porosity Testing..................................................117
5.6.3 56-Day Compressive Strength Testing......................................119
5.6.4 56-Day Porosity Testing..................................................120
5.6.5 Freeze-Thaw Testing......................................................122
5.6.6 Commentary and Conclusions...............................................124
5.6.6.1 Error Bars............................................................124
5.6.6.2 Conclusions...........................................................125
6. Pervious Concrete Field Design...........................................127
6.1 Pervious Concrete Mixture Design.........................................129
6.2 Pervious Concrete System Design..........................................129
7. Pervious Concrete Pavement System Test Section Construction..............131
7.1 Demolition and Excavation................................................133
7.1.1 Demolition of Existing Asphalt Pavement..................................133
7.1.2 Excavation of Sub-Grade Material.........................................135
7.1.3 Verify Elevations........................................................136
7.1.4 Excavate Pipeline Trench.................................................136
7.2 Sub-Base Material Placement..............................................136
7.2.1 Liner....................................................................136
7.2.2 Place Pipe and Coarse Aggregate..........................................138
7.2.3 Geotextile...............................................................138
7.2.4 Sand Layer...............................................................138
7.2.5 Geotextile...............................................................139
7.2.6 Sand Buffer..............................................................140
xii


7.2.7 Coarse Aggregate........................................................140
7.2.8 Trim Liner..............................................................141
7.3 Pervious Concrete Pavement Placement....................................141
7.3.1 Spread the Concrete.....................................................142
7.3.2 Screeding...............................................................143
7.3.3 Compaction..............................................................144
7.3.4 Jointing................................................................145
7.3.5 Edging..................................................................146
7.3.6 Curing and Protection...................................................147
7.4 Finishing Touches.......................................................149
7.5 Construction Modifications..............................................150
8. Field Testing and Monitoring............................................152
8.1 Laboratory Testing Phase VII: Lot K Field Samples.......................152
8.1.1 Conclusions.............................................................155
8.2 Field Testing Phase I: Deterioration and Clogging Monitoring............157
8.3 Laboratory Phase VIII: First Flush Simulation...........................159
8.4 Field Testing Phase II: Stormwater Quality..............................163
8.5 Field Testing Phase III: Heat Island Effect.............................168
8.6 Field Testing Phase IV: Drain Time / Clogging Test......................173
8.6.1 Drain Time Testing Methodology..........................................173
8.6.2 Drain Time Testing (All Sites)..........................................175
8.6.3 Drain Time Testing (Monthly Monitoring of Lot K)........................177
8.6.4 Correlation with Porosity...............................................178
8.6.5 Drain Time / Clogging Testing Conclusions...............................179
9. Failure Mechanism Investigations........................................180
9.1 Laboratory Testing Phase IX: Chemical Interaction with Deicing Agents...180
9.1.1 Deicer Testing Methodology..............................................181
9.1.2 Modifications to ASTM Testing Procedure.................................183
9.1.3 Deicing Chemicals.......................................................185
9.1.4 Results.................................................................186
9.2 Torsional Tire Motion...................................................191
9.3 Freeze-Thaw Conditions..................................................192
9.3.1 The Impervious Zone.....................................................193
9.4 Improper Mixture Design.................................................193
9.5 Improper Placement and/or Curing........................................194
10. Conclusions and Recommendations.........................................196
10.1 Summary of Work Completed...............................................196
10.2 Sustainability Aspects..................................................194
10.3 Pervious Concrete Recommendations.......................................199
10.3.1 General Recommendations..............................................199
10.3.2 Materials and Mixture Design Recommendations.........................201
10.3.3 Placement and Curing Recommendations.................................202
10.4 Recommendations for Future Research.....................................204
Appendix
A. Preliminary Pervious Concrete Literature Review................................206
B. Photographic Record of PCP Installations in Denver Metropolitan Area...........221
xiii


C. UDFCD PCP Moratorium.....................................................278
D. UDFCD Letter of Endorsement..............................................279
E. Laboratory Testing Mixture Designs.......................................281
F. Laboratory Testing Freeze-Thaw Discs.....................................316
G. Auraria Campus Dedication of Parking Lot K...............................324
H. Lot K Installation Bestway Concrete Batch Tickets........................325
I. Lot K PCP Test Section Construction Photographs..........................326
J. Metro Wastewater Reclamation District Stormwater Chemical Analysis Results. 340
K. Compressive Strength Testing Photographs.................................361
Bibliography ...........................................................375


FIGURES
Figure
1.1 Flow Chart of Research Progression...........................................3
2.1 Pervious Concrete............................................................9
2.2 Porous Asphalt...............................................................9
2.3 Modular Block Pavers........................................................10
3.1 UDFCD Pervious Concrete Pavement Section Design.............................19
3.2 PCA Typical Cross Section of Pervious Concrete Pavement.....................20
3.3 Recycled Concrete used for the Aggregate Base Layer in the Field Application ... 34
3.4 Recycled Concrete used for the Aggregate Base Layer in the Field Application .. 35
3.5 Sand / Crushed Glass Mixture used for the Fine Aggregate Layer in the Field
Application.................................................................37
4.1 Pervious Concrete Pavement at Colorado Hardscapes ..........................45
4.2 Pervious Concrete Pavement at Colorado Hardscapes (Typical Condition).......46
4.3 Pervious Concrete Pavement at Colorado Hardscapes ..........................47
4.4 Typical Condition of PCP at Colorado Hardscapes.............................47
4.5 Pervious Concrete Pavement at Colorado Hardscapes (Surface Sealing).........48
4.6 Photograph of Pervious Concrete at Safeway April 2005 ....................49
4.7 Photograph of Pervious Concrete at Safeway April 2005.....................50
4.8 City of Lakewood Pervious Concrete Parking Lot and Tributary Catchment......51
4.9 Pervious Concrete Pavement at City of Lakewood Maintenance Facility.........52
4.10 Pervious Concrete Pavement at City of Lakewood Maintenance Facility ........52
4.11 Typical Condition of Large Coarse Aggregate PCP Sub-Section at City of Lakewood
Maintenance Facility........................................................53
4.12 Typical Condition of Small Coarse Aggregate PCP Sub-Section at City of Lakewood
Maintenance Facility........................................................53
4.13 Parking Lot of Wal-Mart Super Center........................................55
4.14 Pervious Concrete section of Wal-Mart Parking Lot...........................55
4.15 Typical Condition of PCP at Wal-Mart Parking Lot............................56
4.16 Pothole in Pervious Concrete in Main Aisle of Wal-Mart Parking Lot..........56
4.17 Pervious Concrete at Bestway Concrete, Denver...............................58
4.18 Typical Condition of PCP Section Near Office of Bestway Concrete, Denver....58
4.19 Typical Condition of PCP Section Near Fence of Bestway Concrete, Denver.....59
4.20 Vitamin Cottage Pervious Concrete Parking Lot...............................60
4.21 Typical Good Condition of Pervious Concrete on North side of Vitamin Cottage... 60
4.22 Typical Poor Condition of Pervious Concrete on East side of Vitamin Cottage.61
4.23 Extreme Condition of Pervious Concrete on East side of Vitamin Cottage......61
4.24 Surface sealing of Pervious Concrete at Vitamin Cottage.....................62
4.25 Pervious Concrete Pavement in Parking Lot K on the Auraria Campus of the
University of Colorado at Denver............................................63
4.26 Typical Condition of PCP Test Section in Parking Lot K on the Auraria Campus of
the University of Colorado at Denver........................................63
5.1 Test Block Core Drill Mounting Platform.....................................72
5.2 Freeze-Thaw Beam for Phase I Mixture 2......................................82
xv


5.3 Phase I Typical Condition of Freeze-Thaw Beams at three days (12 Freeze-Thaw
Cycles)....................................................................84
5.4 Phase I Condition of Freeze-Thaw Beam for Mixture 2 at three days (12 freeze -
thaw cycles)...............................................................85
5.5 Phase I Condition of Freeze-Thaw Beams at 3 days (12 freeze thaw cycles). 85
5.6 Cylinders from Laboratory Testing Phase II.................................90
5.7 Porosity vs. Compressive Strength Testing Results of the Mini-Mixtures.....94
5.8 28-Day Compressive Strength Testing Results for Laboratory Phase IV and
Phase V....................................................................96
5.9 28-Day Porosity Testing Results for Laboratory Phase IV and Phase V........98
5.10 56-Day Compressive Strength Testing Results for Laboratory Phase IV and
Phase V...................................................................100
5.11 56-Day Porosity Testing Results for Laboratory Phase IV and Phase V.......102
5.12 Freeze-Thaw Testing Results for Laboratory Phase IV and Phase V...........106
5.13 Effect of Fly Ash on Freeze-Thaw Resistance...............................107
5.14 Photograph of Impervious Zone Formation...................................110
5.15 28-Day Compressive Strength Testing Results for Laboratory Phase VI.......116
5.16 28-Day Porosity Testing Results for Laboratory Phase VI...................117
5.17 Porosity vs. Compressive Strength Testing Results at 28-Days of Age for
Laboratory Testing Phase VI...............................................118
5.18 56-Day Compressive Strength Testing Results for Laboratory Phase VI.......119
5.19 56-Day Porosity Testing Results for Laboratory Phase VI...................121
5.20 Porosity vs. Compressive Strength Testing Results at 56-Days of Age for
Laboratory Testing Phase VI...............................................122
5.21 Freeze-Thaw Testing Result for Laboratory Phase VI........................124
6.1 Map of Auraria Campus of the University of Colorado at Denver.............127
6.2 Aerial Photograph of Parking Lot K Test Section Location..................128
6.3 Aerial Photograph of Parking Lot K Test Section Location..................128
6.4 As-Built Construction Details for Parking Lot K...........................130
7.1 PCP Test Section Construction Flow Chart..................................132
7.2 Saw cutting the existing asphalt..........................................133
7.3 Demolition of the existing asphalt pavement...............................134
7.4 Demolition of the existing asphalt pavement...............................134
7.5 Excavation of sub-base area for pervious concrete test section............135
7.6 Positive Lap of Liners....................................................137
7.7 Pipe and Coarse Aggregate Placed in Trenches..............................138
7.8 Placement of Sand / Crushed Glass Layer...................................139
7.9 Placement of the Coarse Aggregate (Recycled Concrete) layer...............140
7.10 Pervious Concrete out of the truck........................................141
7.11 Strike-Off and Compaction of Pervious Concrete with a steel roller screed.144
7.12 Compaction of Pervious Concrete with a small roller.......................145
7.13 Placement of Joint in Pervious Concrete...................................146
7.14 Pervious Concrete Edging..................................................147
7.15 Pervious Concrete Placement Procedures....................................148
7.16 Concrete Wall............................................................150
7.17 Negative Lapping of Liners...............................................151
8.1 Freeze-Thaw Testing Results for Laboratory Phase VII......................155
8.2 Sediment Deposited on Parking Stall #6....................................158
8.3 Photograph of Scrape on Pervious Concrete.................................159
XVI
I


8.4 First Flush Simulation Test Column........................................160
8.5 Filtering Capabilities of Pervious Concrete System........................168
8.6 Pavement Temperature Variations with Air Temperature......................171
8.7 Temperature Reduction of Pervious Concrete Pavements......................172
8.8 Drain Time Testing Apparatus..............................................174
8.9 Correlation between Porosity and Drain Time...............................178
9.1 ASTM C 672 Visual Rating Scale............................................182
9.2 Inverted Deicer Testing Set-Up............................................184
9.3 Apex Sample Deicer Testing at 33-Cycles...................................186
9.4 Control Sample Deicer Testing at 33-Cycles................................187
9.5 Control Sample Deicer Testing at 50-Cycles................................188
9.6 Apex Sample Deicer Testing at 50-Cycles...................................188
9.7 Salt Brine Sample Deicer Testing at 50-Cycles.............................189
9.8 Potassium Acetate Sample Deicer Testing at 50-Cycles......................189
10.1 Pothole in Pervious Concrete Pavement in Parking Lot Isle ................200


TABLES
Table
1.1 Outline of Chapters in the Text, Corresponding Phases of Work and Objectives.... 5
3.1 Summary of Pervious Concrete Materials Recommendations................24
3.2 Summary of Pervious Concrete Mixture Proportions Recommendations......28
3.3 Waste-Stream Material Replacement Alternatives for Pervious Concrete
Pavement System.........................................................31
3.4 Waste-Stream Material Cost and Availability Comparison (Kocman, 2008)...39
3.5 48-Hour Lechate Batch Test Results (Kocman, 2008).......................40
3.6 Recycled Concrete pH Monitoring Through Multiple Flushes (Kocman, 2008).40
5.1 Laboratory Testing Phase I: Compressive Strength Testing Results at
28-Days of Age..........................................................83
5.2 Mini-Mixture Design.....................................................92
5.3 Mini-Mixture Testing Results............................................93
5.4 28-Day Compressive Strength Testing Results for
Laboratory Phase IV and Phase V........................................96
5.5 28-Day Porosity Testing Results for Laboratory Phase IV and Phase V.....98
5.6 56-Day Compressive Strength Testing Results for
Laboratory Phase IV and Phase V........................................100
5.7 56-Day Porosity Testing Results for Laboratory Phase IV and Phase V....101
5.8 Freeze-Thaw Testing Results for Laboratory Phase IV and Phase V........104
5.9 Freeze-Thaw Cycles to Failure Testing Results for
Laboratory Phase IV and Phase V........................................105
5.10 28-Day Compressive Strength Testing Results for Laboratory Phase VI....116
5.11 28-Day Porosity Testing Results for Laboratory Phase VI................117
5.12 56-Day Compressive Strength Testing Results for Laboratory Phase VI....119
5.13 56-Day Porosity Testing Results for Laboratory Phase VI................120
5.14 Freeze-Thaw Testing Results for Laboratory Phase VI....................123
5.15 Freeze-Thaw Cycles to Failure Testing Results for Laboratory Phase VI.123
8.1 28-Day Compressive Strength Testing Results for Laboratory Phase VII.152
8.2 28-Day Porosity Testing Results for Laboratory Phase VII...............153
8.3 56-Day Compressive Strength Testing Results for Laboratory Phase VII...153
8.4 56-Day Porosity Testing Results for Laboratory Phase VII...............153
8.5 Freeze-Thaw Testing Results for Laboratory Phase VII...................154
8.6 Freeze-Thaw Cycles to Failure Testing Results for Laboratory Phase VII.154
8.7 Comparison of Field and Laboratory Mixtures............................156
8.8 Chemical Analysis of First Flush Simulation............................162
8.9 Chemical Analysis of Storm Events......................................165
8.10 Urban Heat Island Temperature Data.....................................170
8.11 Drain Time Testing Results (All Locations).............................176
8.12 Drain Time Monthly Monitoring of Parking Lot K.........................177
8.13 Laboratory Phase V: Porosity and Drain Time Testing....................178
9.1 Comparison between Phase I Mixture 1 and Phase IV Mixture 1............195
A. 1 Preliminary Pervious Concrete Literature Review........................207
XVIII


1. Introduction and Scope
The adverse impacts of urban development on natural watercourses and
associated infrastructure have been well documented. These impacts stem from the loss of
natural infiltration, evaporation, and transpiration functions as pervious vegetated areas are
replaced with impervious surfaces such as buildings and paved surfaces. As less rainwater
infiltrates the ground or returns to the air through evaporation and transpiration, termed
evapotranspiration, more rainwater flows over the pavement surface, carrying with it a
variety of pollutants that ultimately contaminate river ecosystems. Additionally, the higher
runoff volumes result in the erosion of stream channels, flooding, and damage to
stormwater infrastructure.
Stormwater Best Management Practices (BMPs) have emerged as mitigating
solutions to the unfavorable effects inherent to conventional urban development practices.
One such BMP for stormwater management is pervious concrete pavement (PCP).
Pervious concrete can be used in a number of conventional pavement applications, such
as parking lots and sidewalks. However, when compared with conventional pavement
materials such as asphalt and concrete, pervious concrete offers the added benefit that it
can be designed to function as a stormwater detention system. The design of pervious
concrete pavement systems, as with many Best Management Practices, is still evolving.
The dynamic status of pervious concrete is especially true in Colorado due to a
combination of unique climatalogical characteristics and a lack of long-term performance
history. As such, the current design recommendations present an opportunity to
incorporate waste-stream materials to offset virgin and imported raw materials.
1


Sustainability in the urban environment must provide for the needs of residents in
the short and long term while also supporting environmental, social, and economic
resources. Sustainability, as it relates to urban water, must take into account both quality
and quantity of water resources, as well as beneficial reuses of urban waste-streams now
and into the future. Many communities in Colorado face water challenges to meet the
needs of a growing population and address the effects of changing land uses on the water
supply. At the same time, many communities in the U.S. are aiming toward zero-waste,
diverting several urban waste-streams to beneficial re-use. Therefore, the incorporation of
waste-stream materials into stormwater facilities, such as pervious concrete, effectively
addresses both the stormwater treatment and the material usage aspects of sustainability.
The focus of this dissertation is to evaluate the performance of a waste
incorporated pervious concrete pavement system in Denver, Colorado. This required the
screening of waste-stream materials for suitability, the completion of a multi-stage
laboratory design and testing program to determine an optimal mixture design, the
construction of a pervious concrete test section on the Auraria campus of the University of
Colorado at Denver, and the monitoring of this test section for performance. The
progression of work is summarized in the flow chart of Figure 1.1. For each phase of work,
the flow chart also designates the corresponding section of this dissertation.
2


Literature
Review
Laboratory
Testing
Field
Installation
Field
Testing
Thesis
Preliminary Literature Review
Appendix A
7?
4 Primary Sources .
Section 3.2
Phase I
Section 5.2
Phase II
Section 5.3
*=
Phase I
Mini Mixtures
Section 5.4
Phase VII
Lot K Field
Samples
Section 8.1
----*-
Phase IV
Class F FA & AEA
Section 5.5
Phase VI
Sand
Section 5.6
Phase V
4^ Class C FA
Section 5.5
Phase IX
V Deicer
Section 9.1
Phase VIII
First-Flush
Simulation
Section 8.3
-------A------
Field Installation &
NRMCA Training Course
Chapter 7
l


Proposal -
Phase II Stormwater Quality
Section 8.4
Phase I Monitoring Section 8.2

Phase III Heat Island
Section 8.5
Phase IV Infiltration Rate
Section 8.6
......
Dissertation
Figure 1.1 Flow Chart of Research Progression


A comprehensive literature review revealed significant discrepancies regarding
mixture design specifications. The preliminary laboratory testing evaluated the spectrum of
mixture design recommendations and established a base mixture design to exceed specific
structural and hydrologic performance criteria. Subsequent phases of laboratory testing
modified this base mixture design with varying amounts of Class C and Class F fly ash,
fine aggregate, and air-entraining admixture to establish acceptable limits for each.
The field testing included the comprehensive monitoring of the Auraria Campus of
the University of Colorado at Denver pervious concrete pavement test section for reduction
in the heat-island effect, water quality, deterioration, clogging and permeability. In addition,
a number of investigations were completed to examine the suspect causes of deterioration
of PCP in Colorado.
1.1 Research Objectives
The objectives of this research are to:
1. Select the most appropriate waste material re-use for sustainable pervious
concrete pavement system design (including the pervious concrete and
underlying coarse and fine aggregate layers).
2. Design and construct a PCP test-section and develop a standard operating
procedure for construction.
3. Evaluate the structural and hydrological performance of waste incorporated
PCP.
4. Evaluate possible causes of PCP deterioration in Denver, Colorado.
4


This dissertation contains ten chapters. Table 1.1 presents an outline of the
chapters in the text, the corresponding phases of work, and the objectives addressed by
each chapter.
Table 1.1 Outline of Chapters in the Text, Corresponding Phases of Work and
Objectives
Chapters in the Text Phases of Work Objective
1. Introduction and Scope Background NA
2. Stormwater Best Management Practices Background / Literature Review NA
3. Literature Review Literature Review 1
4. Background: Pervious Concrete Pavements in Denver, Colorado Background 4
5. Laboratory Testing of Pervious Concrete Pavement Laboratory 1,2, 3&4
6. Pervious Concrete Field Design Field 1 & 2
7. Pervious Concrete Pavement System Test Section Construction Field 2
8. Field Testing and Monitoring Laboratory / Field 3
9. Failure Mechanism Investigations Laboratory / Field / Summary 4
10. Conclusions and Recommendations Summary 1,2, 3 & 4
Chapters 1, 2, 3 and 4 provide the literature review and background for the work
completed in both the laboratory and field testing phases of this research. Chapters 1 and
2 provide background information without specifically addressing any of the objectives of
this research. Chapter 3 contains the literature review on pervious concrete pavements.
Included in this chapter is a discussion of the applicability of certain waste-stream materials
considered for use in the pervious concrete system, thus, addressing objective 1. Chapter
4 contains the background on the use of PCP in the Denver metropolitan area, discusses
the current condition at each of these sites, and the failures witnessed to date, thus
addressing objective 4.
5


Chapter 5 contains the methodology and results for work completed through six
phases of laboratory testing. This laboratory testing examined numerous pervious concrete
mixtures with varying amounts of fly ash replacement for Portland cement, hence,
addressing objective 1. These mixtures were tested in the laboratory for compressive
strength and porosity, addressing objective 3. Laboratory work also included analyzing the
freeze-thaw resistance, which is a possible cause of the deterioration of pervious concrete
pavements in Denver, thus, addressing objective 4. The purpose of this laboratory testing
was to establish a PCP mixture design to be utilized in the field application that would
maximize the incorporation of waste-stream materials without compromising the structural
or hydrological properties. As such, the laboratory work discussed in Chapter 4 indirectly
addresses objective 2.
Chapter 6 contains information on the field design of the pervious concrete system
(pervious concrete and underlying sub-base layers). This directly addresses objective 2.
Additionally, this chapter describes the waste-stream materials utilized in the field
application, addressing objective 1.
Chapter 7 includes a detailed description of the PCP installation in Lot K on the
Auraria Campus of the University of Colorado at Denver, addressing objective 2.
Chapter 8 provides field testing and monitoring results, thus addressing objective
3. Additionally, this chapter contains the results of the deicer testing, a possible failure
mechanism, addressing objective 4.
Chapter 9 discusses each of the suspected causes of deterioration, directly
addressing objective 4. Each of the suspected causes of deterioration is discussed in
relation to the research completed in this study.
Chapter 10 provides a summary of the work completed and recommendations for
pervious concrete placement. Additionally, this chapter outlines specific areas for future
6


research. This chapter summarizes the work completed, thus re-addressing all four of the
objectives of this research.
Supplementary information is provided in the appendices. Appendix A provides the
preliminary literature review. A photographic record of the pervious concrete installations in
the Denver metropolitan region is provided in Appendix B. The Urban Drainage and Flood
Control District moratorium on pervious concrete pavements is included as Appendix C,
and their letter of endorsement for this research is included as Appendix D. Appendix E
provides the mixture designs utilized throughout the multi-phased laboratory testing
regime. Appendix F contains the freeze-thaw discs from the laboratory testing. Appendix G
contains the dedication letter from the Auraria Higher Education Center dedicating Parking
Lot K for this research project. The batch tickets for the pervious concrete installed in the
test section on Parking Lot K are included as Appendix H. A photographic record of the
pervious concrete construction in Parking Lot K on the Auraria Campus of the University of
Colorado Denver is provided in Appendix I. The water quality analysis results are provided
as Appendix J.
7


2. Stormwater Best Management Practices
Stormwater Best Management Practices are structural and nonstructural
stormwater management control measures taken to mitigate changes to both quantity and
quality of runoff caused through changes in land use. Generally, BMPs focus on treating
stormwater from increased impervious surfaces resulting from development. BMPs are
designed to reduce volume, peak flows, and/or non-point source pollution through
evapotranspiration, infiltration, detention, filtration and/or biological or chemical actions.
Examples of structural BMPs include sedimentation facilities (such as grass swales,
porous landscape detention areas, sand filters, retention ponds, etc.) and porous
pavements (such as pervious concrete, porous asphalt and modular block pavements)
(UDFCD 2003). These practices are generally used in Low Impact Development
applications.
The research in this dissertation focuses on a particular porous pavement, that
being pervious concrete. Figure 2.1 is a photograph of a pervious concrete pavement.
Porous asphalt and modular block pavers, additional types of porous pavements, are
shown in Figure 2.2 and Figure 2.3 respectively.
8


Figure 2.1 Pervious Concrete
Figure 2.2 Porous Asphalt
9


Figure 2.3 Modular Block Pavers
2.1 The Adverse Impacts of Urban Development
When land is developed, the hydrology, or the natural cycle of water is disrupted
and altered. Clearing removes the vegetation that would intercept, slow and return rainfall
to the air through evaporation and transpiration. Grading flattens hilly terrain and fills in
natural depressions that would provide temporary storage of stormwater runoff. The topsoil
and layers of decaying leaves and other organic materials which absorbed preliminary
precipitation are removed and the remaining subsoil is compacted. Rainfall that once would
seep into the ground now flows off the surface. The addition of buildings, roadways,
parking lots, and other impervious surfaces further reduces infiltration and increases
stormwater runoff volumes.
Depending on the degree of changes to the land surface, the total runoff volume
can increase dramatically. These changes to the landscape not only increase the total
10


volume of runoff, but also increase the velocity with which the runoff flows across the land
(Debo and Reese 2003). This effect is further exacerbated by drainage systems such as
gutters, storm sewers, and lined channels that are designed to quickly carry runoff to rivers
and streams.
Development and the resulting impervious surfaces reduce the amount of water
that infiltrates into the soil and groundwater, thus reducing the amount of water that can
recharge aquifers and feed stream flow during periods of dry weather (Gran 2007).
Development and urbanization affect both the quantity and quality of stormwater
runoff. Development increases both the concentration and types of pollutants carried by
runoff (Maxted and Shaver 1998). As it flows over rooftops, lawns, parking lots and
roadways, stormwater collects and transports a variety of contaminants and pollutants to
downstream water bodies (Gran 2007). Additionally, the loss of the original topsoil and
vegetation removes a valuable filtering mechanism for stormwater runoff (Debo and Reese
2003).
The cumulative impact of development and urban activities, and the resulting
changes to both stormwater quantity and quality in the entire land area that drains to a
stream, river, lake, or estuary determine the conditions of that water body. Urban
development within a watershed has a number of direct impacts on downstream waters
and waterways. These include changes to stream flow and geometry, degradation of
aquatic habitats, and water quality effects (Gran 2007).
11


2.2 Urban Drainage and Flood Control District
The Urban Drainage Flood Control District (UDFCD) was established by the
Colorado legislature in 1969 for the purpose of assisting local governments in the Denver
metropolitan area with multi-jurisdictional drainage and flood control problems (UDFCD
2008). The UDFCD has developed design criteria for stormwater management systems
and compiled a comprehensive list of installation and maintenance instructions for BMPs
specific to the Denver metropolitan area. Volume 3 of the 2008 UDFCD Storm Drainage
Criteria Manual provides guidance for the selection and design of stormwater quality
BMPs. Pervious concrete pavement is among the BMPs included in Volume 3 of the
UDFCD Criteria Manual, and those recommendations were used in this study.
12


3.
Literature Review
Pervious concrete is a unique and effective means to address important
environmental issues and support sustainable growth. By capturing stormwater and
allowing it to seep into the ground, pervious concrete is capable of recharging
groundwater, reducing stormwater runoff and meeting U.S. Environmental Protection
Agency (EPA) stormwater regulations. In so doing, the pervious concrete system is an
effective means to filter a number of contaminants from the stormwater (Park 2002). In
fact, the use of pervious concrete is among the BMPs recommended by the EPA and other
agencies and engineers across the country for the management of stormwater runoff. This
pavement technology creates more efficient land use by eliminating the need for retention
ponds, swales, and other stormwater management devices.
In pervious concrete, carefully controlled amounts of water and cementitious
materials are used to create a paste that forms a thick coating around aggregate particles.
A pervious concrete mixture contains little or no sand, thus creating a substantial void
content. Using sufficient paste to coat and bind the aggregate particles together creates a
system of highly permeable, interconnected voids that drain quickly. Typically, between
15% and 25% voids are achieved in the hardened pervious concrete, and flow rates for
water through pervious concrete are approximately 480 in/hr (1219 cm/hr) (Tennis, et al.
2004). Pervious concrete has a comparable or slightly reduced strength when compared
to conventional concrete mixtures, but sufficient strength for many applications is readily
achieved. The compressive strength of different PCP mixtures can range from 500 to 4000
psi (3.5 to 27.5 MPa) (Kosmatka, et al., 2002).
13


While pervious concrete can be used for a surprising number of applications, its
primary use is in pavement. This research focuses on the pavement applications of the
material, which also has been referred to as porous concrete (Kosmatka, et al., 2002),
permeable concrete (Tennis, et al, 2004), no-fines concrete (Kosmatka, et al., 2002), gap-
graded concrete (Tennis, et al, 2004), and enhanced-porosity concrete (Tennis, et al,
2004).
Other applications of pervious concrete include (Tennis, et. al., 2004):
low-volume streets, highway shoulders, alleys and driveways
sidewalks
low water crossings
sub base for conventional concrete pavements
patios
slope stabilization
foundations / floors for greenhouses, fish hatcheries, aquatic centers, and zoos
noise barriers
walls
Pervious concrete was first used in 1852 (Ghaforri and Dutta 1995), and although
not a new technology, it is receiving renewed interest, partly due to federal clean water
legislation. Unfortunately, as pervious concrete mixture designs and sub grade system
designs are still evolving, standardized designs and procedures have yet to be established.
This poses a number of difficulties. A number of agencies have released
recommendations for the mixture design of pervious concrete and for the overall system
design (including base materials). However, many of the recommendations vary among the
sources and in some cases are in direct contradiction with each other. Therefore, the
14


experience and knowledge of an experienced pervious concrete craftsman in the local
vicinity is an important resource. The design and construction of pervious concrete needs
to account for the local environment and climate, thereby necessitating regionally based
specifications.
An additional challenge is the limitation of testing procedures. Something as
fundamental as a compressive strength test is well established for standard concrete
(ASTM C 39 [2005]) but poses a whole new challenge with pervious concrete, as no
formalized testing procedures are yet established. Similarly, the procedures to examine
conventional concretes resistance to freeze-thaw are well established (ASTM C 666
[2003]). However, the testing methodology with standard concrete requires one to test for
the fundamental transverse frequency. Due to the inherent void structure within a pervious
concrete, the transverse frequency cannot be measured, and consequently this
deterioration must be measured by another means. Additionally, ASTM standard C672
provides guidelines for evaluating the scaling resistance of concrete surfaces exposed to
deicing chemicals. This test requires that a dike be constructed to hold the deicer chemical
atop the concrete specimen whilst being subjected to freezing and thawing. However, for
the pervious concrete samples, this testing set-up is not feasible as the deicer would drain
through the sample. Therefore, modified laboratory procedures were developed for the
purposes of this research. One of the advantages of the dynamic status of pervious
concrete design is that it provides the opportunity to explore the possibility of incorporation
of waste-stream materials into the design. However, one extreme difficulty was the lack of
standardized testing methodologies.
15


3.1 Recommendations and Applications
A preliminary literature review uncovered more than one hundred
recommendations, applications and studies on pervious concrete. Appendix A provides a
comprehensive tabular listing of the research examined in the preliminary literature review.
For each source examined in this preliminary literature review, the corresponding research
category or categories were identified:
Applications and Case Studies
Construction Techniques
Durability and Maintenance
Hydrological and Environmental Design
Mixture Design
Specifications and Test Methods
Structural Design and Properties
In southeastern states such as Florida and Georgia, pervious concrete has been in
use for over a decade to mitigate the environmental impacts of development, where it is
recognized as an effective solution to the stormwater runoff problem (Arakawa 2008). The
success of pervious concrete in milder climates has led to increasing interest into
expanding the use of the technology into other areas of the country. As the use of pervious
concrete has spread throughout the U.S., questions have arisen as to how durable the
material will be in various environmental conditions. Of particular concern are
environments which typically experience freezing and thawing, such as the semi-arid
climate of Denver, Colorado. When water freezes, it expands, generating forces within
materials that can break them apart. Pervious concrete pavement recommendations
specific to the semi-arid climate characteristic of Denver, Colorado are extremely limited.
16


Additionally, as pervious concrete design is still evolving, the recommendations from
different sources had great variability.
This literature review was used as the basis for the testing completed in the first
phase of laboratory testing, which will be discussed further in Section 5.2. After completing
this phase of testing it was evident that a more thorough review needed to be completed of
mixture design materials and proportioning from a limited number of sources. Therefore,
after a preliminary review of the available literature, three national references and one
specific to the Denver metropolitan region were used as the primary references for the
remaining phases of this research. These primary sources were:
Urban Drainage and Flood Control District Criteria Manual Volume 3 (Urban
Drainage and Flood Control District 2003)
Pervious Concrete Pavements (Tennis, et al. 2004)
Pervious Concrete Contractor Certification Text Reference (National Ready Mixed
Concrete Association 2007)
ACI 211.3 Guide for Selecting Proportions for No-Slump Concrete (American
Concrete Institute 1997)
Each of these references and the recommendations suggested, are discussed in more
detail in the following sections.
3.1.1 Urban Drainage and Flood Control District Recommendations
Volume 3 of the UDFCD Storm Drainage Criteria Manual provides guidance for the
selection and design of stormwater quality best management practices, including pervious
concrete. The specifications provided by UDFCD for Portland cement pervious concrete
pavement are based on the specifications recommended by the Georgia Concrete and
17


Products Association (GCPA). The dry, high-altitude climate along with freeze-thaw cycles
that are rarely an issue in Georgia required modifications to the provisions specified by
GCPA. The UDFCD pervious concrete recommendations were based on those of GCPA
partly because, at the time of publication, there was not yet any experience in Colorado
with this type of pavement. Therefore, all pervious concrete applications completed using
these specifications were to be viewed as experimental until sufficient field experience was
gained in the local environment.
The GCPA recommendations were modified by UDFCD for use in the Denver area
so as to recognize the differences in rainfall, deicing methods, freeze-thaw conditions, and
humidity. Modifications were made after discussion with Villanova University and their
experiences with this type of pavement. The UDFCD released these recommendations as
interim technical specifications with the potential for future modifications based on field
experience. The primary differences from the specifications recommended by GCPA are
the prohibition on use of curing accelerants and additives and restrictions on temperature
for placing the concrete.
Figure 3.1 displays the cross-sectional view of the UDFCD recommended pervious
concrete system. The materials and proportioning details specified by UDFCD are provided
in Sections 3.2 and 3.3 respectively.
18


Woven geotextile as specified on this drawing .
Wrap on d/s side to within 1 inch of top base course. \
Instal 16 MIL (min.)
impermeable membrane
under pipe & wrap it on d/s
side to within 1in( apMT) of
top of gravel to serve as
horizontal flow barrier.
Schedule 40 HOPE 3' to
4* underdrain
Space at 20 O.C. (max.)
Slope = 1.0% (min.)
Fill trench with same
gravel used in
Base Course.
May efiminate if site is
suitable for infiltration.
Monoilhicdly poured porous concrete
(mix of AASHTO #8 or 067 gravel
and
Portland cement per specifications in
the BMP Details and Specifications
Chapter of this Manual)
D 0.67(r) mnr
6* (mri)
Woven geotextle fabric meeting:
A STM D4751 AOS US Std. Sieve #50 to 070.
A STM D4633 min. trapezoidal tear strength 100 x 60 t>s.
Minimum COE specified open area of 4%.
When certified tests show percolation rates of less than
60 minutes per inch of draw dawn under the PP bottom
and infltration is alowed. eliminate the bottom sand
oyer and underdrains.
When Tyoe C sols are present and when infilrafion is
allowed, unless pe rcoi art ions show otherwise, eliminate
the bottom sand layer, use underdrains and geotextle
finer instead of an impermeable one under the gravel.
When the underlying soils are NRCS Type D or expansive,
when existing or proposed building is within 10 feet, antfor
when land uses pose risk to groundwater contamination,
use 16 mi minimum thickness impermeable finer under
and on sides of the pavement sand and gravel media.
Poured Concrete Porous Pavement (PCP) Section
with an Underdrain System
Figure 3.1 UDFCD Pervious Concrete Pavement Section Design (UDFCD 2003)
3.1.2 Portland Cement Association Recommendations
In 2004, the Portland Cement Association (PCA) published a guide to pervious
concrete pavements. This manual reviews the applications of pervious concrete and its
engineering properties, including environmental benefits, structural properties and
durability. Both hydraulic and structural designs of pervious concrete pavements were
discussed, as well as construction techniques. As shown in Figure 3.2, the system design
followed the same general principles as the UDFCD design. However, the design criteria
were less specific than UDFCDs recommendations.
19


Curb
i ,* * /
Pervious concrete surface V
# / v *
' N \ t / 7> _ * * ..a.-- * : *.*.* *.* */,**'*V v .**,* Subbese *V- ; ::*V: V' *':;.**: *** *,*_ *, # *** 1 ,* ***, */ ,** *,* ***i
Figure 3.2 PCA Typical Cross Section of Pervious Concrete Pavement
(Tennis, et al. 2004)
The materials and proportioning details published in this manual are provided in Sections
3.2 and 3.3 respectively.
3.1.3 National Ready Mixed Concrete Association Recommendations
The National Ready Mixed Concrete Association (NRMCA) published a text
reference for the Pervious Concrete Contractor Certification Workshop. This text reference
provided the practical information needed to successfully place pervious concrete. The
cross-sectional design provided in this text manual is similar to that provided in the PCA
Pervious Concrete Pavements text, shown in Figure 3.2. The materials and proportioning
details specified in this manual are provided in Sections 3.2 and 3.3 respectively.
The University of Colorado Denver along with the Colorado Ready Mixed Concrete
Association (CRMCA) hosted a 2-day NRMCA Pervious Concrete Contractor Certification
Workshop on July 21, 2008. The pervious concrete in Parking Lot K of the Auraria Campus
of the University of Colorado Denver, located in downtown Denver, Colorado, was placed
20


by the students in the certification class. At which time, the author and one of the primary
faculty advisors were certified as Pervious Concrete Craftsmen.
3.1.4 American Concrete Institute Recommendations
ACI 211.3 provided a guide for selecting proportions for no-slump concrete.
Appendix 7 of this guide provided specifications for pervious concrete mixture
proportioning and is summarized in Section 3.3. This reference does not provide any
information regarding applications or case studies, construction techniques or placement
details. In addition, durability or maintenance, hydrological or environmental design,
specifications or test methods, structural design or material properties are not provided in
this guide.
3.2 Pervious Concrete Materials
Pervious concrete is comprised of carefully proportioned amounts of cement,
water, and aggregate. Proper mixture design requires that each of these materials meet
certain specifications. The material specifications provided by each of the primary
literature sources are discussed herein and summarized in Table 3.1.
The guidelines and recommendations for the coarse aggregate gradation to be
used in pervious concrete reference ASTM C 33 [2007]. This specification defines the
requirements for grading and quality of fine and coarse aggregate (other than lightweight or
heavyweight aggregate) for use in concrete.
The guidelines and recommendations are in agreement that water to be used in
pervious concrete mixtures must be potable.
21


The guidelines and recommendations for the cement to be used in pervious
concrete were the same as those pertaining to standard concrete. ASTM C 150 [2007]
specifies eight types of Portland cement, as follows:
Type I For use when the special properties specified for any other type are not
required.
Type IA Air-entraining cement for the same uses as Type I, where air-
entrainment is desired.
Type II For general use, especially when moderate sulfate resistance or
moderate heat of hydration is desired.
Type IIA Air-entraining cement for the same uses as Type II, where air-
entrainment is desired.
Type III For use when high early strength is desired.
Type IIIA Air-entraining cement for the same use as Type III, where air-
entrainment is desired.
Type IV For use when a low heat of hydration is desired.
Type V For use when high sulfate resistance is desired.
Some of the guidelines and recommendations only allow for certain types (typically
Type I or Type II) of cement to be used in pervious concrete. In addition to the types of
cement listed above, Urban Drainage allows for the use of portland cement Type IP
(cement / pozzolan blend) or Type IS (cement / slag blend) conforming to ASTM C 595
[2008], This specification pertains to blended hydraulic cements for either general and
22


special applications, using slag or pozzolan, or both, with Portland cement or Portland
cement clinker or slag with lime.
As part of this research, partial fly ash replacement for Portland cement was used
in a number of the mixtures tested. There is significant discrepancy amongst the primary
literature sources as to the acceptable amount of fly ash replacement for cement. The
UDFCD does not recommend the use of any fly ash in pervious concrete (Urban Drainage
and Flood Control District 2003). Whereas, the NRMCA pervious concrete training
reference states that fly ash can replace up to 25% of the Portland cement in a given
mixture (National Ready Mixed Concrete Association 2007).
Certain chemical admixtures may be added to the pervious concrete mixture. The
guidelines and recommendations for the use of admixtures in pervious concrete commonly
refer to ASTM C 494 [2008], This specification provides standard specification for chemical
admixtures in concrete. This specification covers materials for use as chemical admixtures
to be added to hydraulic-cement concrete mixtures in the field for the purposes indicated
for the seven types as follows:
Type AWater-reducing admixtures,
Type BRetarding admixtures,
Type CAccelerating admixtures,
Type DWater-reducing and retarding admixtures,
Type EWater-reducing and accelerating admixtures,
Type /^-Water-reducing, high range admixtures, and
Type GWater-reducing, high range, and retarding admixtures.
23


Additionally, this specification stipulates tests of an admixture with suitable concreting
materials proposed for specific work.
The guidelines and recommendations for the use of air-entraining admixture in
pervious concrete refer to ASTM C 260 [2001]. This specification provides standard
specifications for air-entraining admixtures (AEA) in concrete. This specification covers
materials proposed for use as air-entraining admixtures to be added to concrete mixtures
in the field.
A summary of the recommendations for the material specifications from the four
primary sources is provided in Table 3.1.
Table 3.1 Summary of Pervious Concrete Materials Recommendations
Recommendation / Guideline Source
Type A Water Reducing Admixture shall comply with ASTM C 494 [2008]; however, Phosphorous-based admixtures shall not be used in Porous Concrete Pavement mixtures. Air-Entraining Admixtures shall comply with ASTM C 260 [2001], UDFCD
Because of the rapid setting time associated with pervious concrete, retarders or hydration-stabilizing admixtures are used PCA
(/) commonly. Use of chemical admixtures should closely follow
L_ D manufacturers recommendations. Air entraining admixtures can
"x reduce freeze-thaw damage in pervious concrete and are used
c where freeze-thaw is a concern. ASTM C 494 [2008] governs
(0 chemical admixtures, and ASTM C 260 [2001] governs air-
o p entraining admixtures. Proprietary admixture products that
o also used.
Chemical admixtures used in regular concrete are often used in the production of pervious concrete mixtures. These admixtures are used when conditions warrant. NRMCA
Admixtures to reduce water content and/or to improve workability of concrete shall be used in accordance with the manufacturers instructions and recommendations. UDFCD
24


Table 3.1 (cont.)
Summary of Pervious Concrete Materials Recommendations
Recommendation / Guideline Source
Cement Portland cement should conform to ASTM C 150 [2007], or a combination of cementitious materials meeting the appropriate ASTM specification requirements. ACI
Portland cement as used in regular concrete. NRMCA
Portland Cement Type I or II conforming to ASTM C 150 [2007] or Portland Cement Type IP or IS conforming to ASTM C 595 [2008], UDFCD
! i Coarse Aggregate Use Colorado Department of Transportation (CDOT) No. 67 coarse aggregate (3/4 to No.8) per ASTM C 33 [2007], If other gradation of aggregate is to be used, submit data on proposed material to owner for approval. UDFCD
Commonly used gradations of coarse aggregate include ASTM C 33 [2007] No. 67, No. 8, or No. 89. PCA
Aggregates for pavements should conform to ASTM D 448 [2008], while ASTM C 33 [2007] covers aggregates for use in general concrete construction. PCA
The most common gradation of coarse aggregate used in pervious concrete must meet the requirements of ASTM C 33 [2007] designations No. 8, No. 7 and No.67. ACI
Supplementary Cementitious Materials No Fly ash or Ground Iron Blast-Furnace Slag may be used in the PCP mixture; Fly ash or pot ash shall not be used UDFCD
Fly ash may be used as a replacement for Portland cement up to about 25% replacement. NRMCA
Supplementary cementitious materials (SCMs), such as fly ash and pozzolans (ASTM C 618 [2005]) and ground-granulated blast furnace slag (ASTM C 989 [2005]), may be used. PCA
Water Potable or comply with CDOT Standard Specifications for Portland Cement Concrete water. UDFCD
Water quality is discussed in ACI 301. As a general rule, water that is drinkable is suitable for use in concrete. PCA
Any source of water that is used for the production of conventional concrete can be used in the production of pervious concrete mixtures. Potable water is generally suitable for use as missing water in concrete and other sources of water can be used if they do not significantly impact the setting time, strength or durability of the concrete. NRMCA
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3.3 Pervious Concrete Mixture Proportions
Not only must the correct materials be used, but proper mixture design dictates
that these materials must be used in the correct proportions. Proper proportioning of
materials in a pervious concrete mixture is critical to maximizing strength while maintaining
porosity. The mixture design specifications provided by each of the primary literature
sources are discussed herein and summarized in Table 3.2.
The amount of aggregate used in pervious concrete mixtures is defined by the
weight of the aggregate per a specified volume of concrete. Alternatively, a volume of
aggregate may be specified when calculated as a function of the unit weight determined in
accordance with ASTM C 29 [2007] jigging procedure. This test method covers the
determination of bulk density (unit weight) of aggregate in a compacted or loose condition,
and calculates voids between particles in fine, coarse or mixed aggregates based on the
same determination.
The majority of the guidelines and recommendations reviewed recommended that
no fine aggregate (sand) be used in pervious concrete. However, some allow for the use of
fine aggregate in the pervious concrete mixture up to a ratio of 1:1 with the coarse
aggregate (Tennis, et al. 2004). Jones from Iowa State University stated that 5% to 7% of
the total aggregate must be sand, or material that is retained on the #4 sieve and smaller,
for pervious concrete to be resistant to freeze/thaw damage (Jones 2008). Additionally,
Klemens comments that some concrete producers have found that adding up to 10% sand
26


dramatically improves durability in climates where pavements are subjected to freezing and
thawing (Klemens 2008).
There was significant disagreement among the primary sources with regards to the
amount of cementitious material to be utilized in the mixture design. The UDFCD
recommends that a minimum of 600 lbs of cement per cubic yard of concrete (356 kg per
cubic meter) be utilized (Urban Drainage and Flood Control District 2003). In direct
contradiction with this, the NRMCA Pervious Concrete Contractor reference states that
500-600 lbs of cement per cubic yard of concrete (296.6 356 kg per cubic meter) should
be used (National Ready Mixed Concrete Association 2007). In addition, the PCA
recommends 450 700 lbs of cement per cubic yard (267 415.3 kg per cubic meter).
This range encompasses both the UDFCD and the NRMCA recommendations. With such
significant variability and discrepancy regarding the amount of cementitious material to be
used in the pervious concrete mixture design, it was evident that laboratory testing was
necessary to determine the appropriate proportioning of the cementitious material. Phase
III of laboratory testing was completed in order to meet this need.
There was also disagreement among the primary sources with regard to the water
to cementitious ratio (w/cm) to be used in pervious concrete mixture design. The PCA
recommends a water to cement ratio of 0.27 to 0.34 (Tennis, et al. 2004). The NRMCA
Pervious Concrete Contractor text reference recommends a w/cm of 0.26 to 0.35 (National
Ready Mixed Concrete Association 2007). These two recommendations are in close
27


agreement. However, the ACI recommendation of a w/cm of 0.35 to 0.45 (American
Concrete Institute 1997) is significantly higher than the two previous recommendations.
Therefore, Phase III of laboratory testing evaluated the appropriate w/cm to be used for the
field application.
Table 3.2 contains a summary of the pervious concrete mixture proportioning
recommendations from each of the four primary references. The cementitious materials
content and the w/cm are critical aspects of the mixture design and presented the most
significant discrepancies among the primary sources. Therefore, in Phase III of Laboratory
Testing numerous mini-mixtures were tested to determine the optimal design values for
these proportions.
Table 3.2 Summary of Pervious Concrete Mixture Proportions Recommendations
Recommendation / Guideline Source
Aggregate Content Aggregate content = 2000 to 2500 lb/ydA3 Aggregate to Cement Ratio (by mass) 4 to 4.5:1 Fine to Coarse Aggregate Ratio (by mass) 0 to 1:1 PCA
The volume of aggregate per cu. yd. shall be equal to 27 cu. ft. when calculated as a function of the unit weight determined in accordance with ASTM C 29 [2007] jigging procedure. UDFCD
The dry rodded unit weight of the aggregate, measured in accordance with the jigging procedure in ASTM C 29 [2007], NRMCA
Cementitious Material 450 to 700 lbs. per cu. yd. PCA
Total cementitious material shall not be less than 600 lbs. per cu. yd. UDFCD
500 to 600 lbs. per cu. yd. NRMCA
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Table 3.2 (cont.) Summary of Pervious Concrete Mixture Proportions Recommendations
Recommendation / Guideline Source
Water to Cement Ratio 0.27 to 0.34 The correct water content has been described as giving the mixture a sheen, without flowing off of the aggregate. A handful of pervious concrete formed into a ball will not crumble or lose its void structure as the paste flows into the spaces between the aggregates. PCA
Mixture water shall be such that the cement paste displays a wet metallic sheen without causing the paste to flow from the aggregate. (Mixture water yielding a cement paste with a dull-dry appearance has insufficient water for hydration and shall be rejected.) UDFCD
0.35 to 0.45 AC I
For pervious concrete the w/cm to obtain the needed workability usually falls within 0.26 to 0.35. NRMCA
3.4 Waste-Stream Material Options for Pervious Concrete Pavement System
The design of many Best Management Practice systems are still evolving and new
research leads to upgrades in current recommendations. The current design
recommendations for pervious concrete leave opportunity for the incorporation of waste
symbiosis and holistic design concepts. Local waste-streams offer an opportunity for
replacement of portions of the media. For example, options for the sub-base layers may
utilize waste-stream materials such as recycled concrete (McCambridge et al. 2004) and
crushed glass (Clean Washington Center 1996). The implications of changes to the current
techniques must be evaluated in regards to sustainable design, ensuring:
Local commercial products are identified and analyzed for quality.
Chemicals released from these waste-streams do not release undesirable
compounds, such as nutrients and heavy metals.
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The first step in waste symbiosis is to explore the local sources of waste-stream
replacement for virgin material (cement, concrete aggregate, aggregate base course, and
sand). Table 3.3 presents the options for potential replacement of virgin materials. An initial
literature review provides aggregate replacement options such as recycled concrete,
crushed glass and crushed rubber (Moller and Leger 1998), and cement replacement
options as fly ash. However, the impact of these materials on the combined physical and
chemical performance of the pervious concrete system has not been previously evaluated.
The suitable replacements were evaluated based on cost, availability, quality
control and physical/chemical characteristics. All waste materials must have similar
characteristics such as porosity, bulk density, organic content and water holding/draining
capacity as the virgin material. Concerns of leaching materials from waste-streams will
require comprehensive testing measures. Wastes from industry may be compared to the
Wisconsin state regulations on Beneficial Use of Industrial Byproducts to ensure the safety
of materials (Wisconsin Administrative Code 1998). In addition to being environmentally
safe, general acceptance of incorporating waste-stream materials into pervious concrete
infrastructure requires knowledge that the final system will produce concrete with structural
and durability characteristics that meet or exceed those of ordinary Portland cement
concrete.
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Table 3.3 Waste-Stream Material Replacement Alternatives for Pervious Concrete
Pavement System
Waste-Stream Material Replacement Local Source
Fly Ash Cement Local electric power plants
Recycled Concrete Concrete Aggregate Oxford Recycling Center Recycled Materials Company
Recycled Concrete Aggregate Base Coarse Oxford Recycling Center Recycled Materials Company
Rubber Concrete Aggregate AcuGreen (formerly JaiTire)
Rubber Aggregate Base Coarse AcuGreen (formerly JaiTire)
Crushed Glass Sand City of Durango Rocky Mountain Bottling Co.
3.4.1 Fly Ash Replacement for Cement
Cement production requires a source of calcium (usually limestone), a source of
silicon (such as clay or sand) and small amounts of bauxite and iron (Kosmatka, et.al.,
2002). These raw materials are finely ground and mixed, then fed into a rotary cement kiln.
In the kiln, the raw materials undergo complex chemical and physical changes required to
make them able to react together through hydration. One of the reactions is the bonding of
calcium oxide and silicates to form dicalcium and tricalcium silicates (C2S and C3S). These
react with water to produce calcium-silicate-hydrate (C-S-H) and calcium hydrate (C-H)
(lime).
Fly ash is a by-product of heat generation from thermal coal-fired power plants.
The silica from the fly ash reacts with the already produced C-H to form C-S-H. The silica
in fly ash combines with the calcium hydroxide (CaOH, or free lime) crystals to form more
C-S-H solids, thereby reducing micro cracking and creating less permeable concrete. At
early ages, the fly ash in concrete does not provide a chemical strength matrix; however, at
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later ages the fly ash does form additional C-S-H which results in increased strength. It is
the additional C-S-H at later ages in fly ash concrete that provides increased long-term
strength.
The two main types of fly ash used for concrete additives in the United States are
Class F and Class C. By definition in ASTM C 618 [2005], Class F fly ash comes from
bituminous coal and Class C comes from sub-bituminous coal. In practice however, Class
F comes from bituminous, sub-bituminous, and lignite coals while Class C comes from
sub-bituminous coal (Reiner 2006). Therefore, the ranking of coal by thermal value does
not disclose the chemistry of ash within these two classes. The pozzolanic properties of a
good-quality fly ash are governed primarily by its mineralogy, low carbon content, high
glass content and 75% or more particles finer than the 45 pm sieve (Malhotra and Mehta
2002) (ASTM C 618 [2005] 05 requires a minimum of 66% passing the 45 pm sieve).
Despite the research cited above stating the increased durability, the desire to include fly
ash, or any waste-stream product, is limited by the perception of prescriptive limits.
Reiner tested the performance of several high performance green concrete
(HPGC) mixtures (Reiner 2006). During Reiners laboratory testing, it was found that the
H60 mixture (60% replacement of Portland cement with fly ash) provided excellent
durability results and sufficient strength for use in the field. Therefore, the H60 design
mixture was utilized to produce a Precast Manhole & Lid, an alley panel, and a prestressed
structural double-tee girder and slab. This work exemplifies that fly ash can and has been
successfully used as a partial replacement for Portland cement in high percentages in
ordinary portland cement concrete.
For pervious concrete, the NRMCA recommends a maximum of 25% replacement
of portland cement with fly ash (National Ready Mixed Concrete Association 2007).
However, UDFCD states that no fly ash shall be used in pervious concrete mixtures (Urban
32


Drainage and Flood Control District 2003). With this discrepancy in the acceptable
percentage of fly ash replacement for Portland cement it was clear that laboratory testing
was necessary in order to establish a maximum acceptable amount of fly ash replacement.
This testing was completed in Laboratory Testing Phase IV (Class F fly ash) and Phase V
(Class C fly ash). The field application utilized Class C fly ash.
3.4.2 Recycled Concrete Replacement for Concrete Aggregate
Portland cement concrete can be reclaimed during demolition operations and
crushed into a coarse granular material that can be used as a substitute for crushed virgin
rock. Aggregate processors are beginning to accept reclaimed concrete for a "tipping fee"
significantly lower than the cost of land filling the material and to supply recycled concrete
aggregate of sufficient quality for many applications.
As landfill costs for construction and demolition debris (C&D) continue to rise and
the landfills become heavily regulated, seeking alternative means to dispose of concrete
from C&D operations is becoming an ever increasing fiscally responsible alternative. More
disposal sites are opening and contractors are incorporating recycling into their operations
to decrease disposal costs.
Recycled concrete aggregate is increasingly available and is often an economical
alternative to new aggregate. Project managers can ensure that their contractors are
aware of opportunities to recycle this material and can require the use of recycled material
in construction. Unfortunately, recycled concrete aggregate was not locally available in the
desired size (AASHTO #8) for the aggregate in the pervious concrete mixture and therefore
virgin material was used for both the laboratory and field testing phases of the research.
33


Users of recycled concrete aggregate should take customary precautions to
ensure that the material is suitable for the intended application. Using recycled material in
place of increasingly scarce and expensive native coarse aggregate saves money, as well as
diverts material from the waste-stream.
3.4.3 Recycled Concrete Replacement for Aggregate Base Layer
Fortunately, the size of recycled concrete aggregate needed for the aggregate
base (AASHTO #3 or #4) is locally available. Therefore, 100% replacement of virgin rock
with recycled concrete aggregate was utilized in the field installation for the coarse
aggregate layer of the PCP system. A photograph of the recycled concrete aggregate used
for the coarse aggregate layer is shown in Figure 3.3 and Figure 3.4.
Figure 3.3 Recycled Concrete used for the Aggregate Base Layer in the Field
Application
34


Figure 3.4 Recycled Concrete used for the Aggregate Base Layer in the Field
Application
3.4.4 Rubber Replacement for Concrete Aggregate
Limited research has been completed on the use of rubber as a replacement for
concrete aggregate (Pierce and Blackwell 1999). An example of such a site is in Golden,
Colorado, where rubber replacement for concrete aggregate was utilized in an ordinary
Portland cement concrete curb, gutter and sidewalk application (Petr 2007). The
infrastructure was less than 2 years of age at the time of the visit and severe scaling was
observed. Due to this deterioration, this concrete infrastructure has since been replaced
with standard concrete. These visual observations coupled with the lack of literature
available on the use of rubber as a replacement for concrete aggregate eliminated its use
from further consideration.
35


3.4.5 Rubber Replacement for Aggregate Base Layer
While there has been limited research on the use of rubber as a replacement for
concrete aggregate, no literature was found of its use in an aggregate base coarse.
Additionally, rubber is a flexible material, which would allow for excessive deflections.
Therefore, the use of rubber as a replacement for the aggregate base coarse was
eliminated from further consideration.
3.4.6 Crushed Glass Replacement for Sand
Finding suitable replacements for virgin materials, such as sand, may increase the
sustainability of urban environments and serve the needs of the growing population. The
use of recycled glass cullet in soil media is an intriguing concept.
The use of crushed glass in construction projects is gaining popularity. Recycled
glass cullet (i.e., crushed glass) can be used instead of sand in countless types of projects,
such as embedment material for water and sewer main pipes. Thousands of tons of glass
bottles and jars enter landfills each day. Recycling this glass is an excellent means to
reduce waste, lower construction costs and become more environmentally friendly.
Crushing the glass removes sharp edges, making it as safe to work with as sand or gravel.
In the spring and summer of 1997, the University of Washington Center for Urban
Horticulture (CUH) in Seattle, Washington completed a study on the growth properties of
soil media containing glass cullet (Moller and Leger 1998). Results from this study
suggested that it is feasible to use recycled glass to replace portions of the sand (up to 3/5
replacement by volume) in a standard topsoil mixture with no detectable problems. In
addition, cost savings and a decreased reliance on virgin materials were realized by using
glass in some portion of the mixture.
36


The reuse of local materials is important so as to minimize the transportation (and
thus the embodied energy and cost) required. Although the City of Durango had sufficient
crushed glass to fill the entirety of the sand portion of the pervious concrete test section, it
is located more than 300 miles from Denver. Rocky Mountain Bottling Company, with a
travel distance of 15 miles from the UCD Campus, had the capability of providing 10% of
the total volume required for the sand layer. Therefore, the glass from Rocky Mountain
Bottling Company was mixed in the sand layer of the PCP system. This mixture is shown in
Figure 3.5.
Figure 3.5 Sand / Crushed Glass Mixture used for the Fine Aggregate Layer in the Field
Application
Rocky Mountain Bottling Company works with Coors Brewery to collect glass and
melt it into new beer bottles. The crushed glass utilized in this research consisted of fines
37


scraped off conveyer belts and was donated from Rocky Mountain Bottling Company. This
crushed glass product is not typically available from Rocky Mountain Bottling nor are they
equipped to produce and sell this material. A source of surplus crushed glass is not
readily available in the Denver metropolitan area.
3.4.7 Waste-Stream Material Leaching (Kocman 2008)
The pervious concrete test section installed on the Auraria Campus of the University
of Colorado Denver utilized 100% replacement of the coarse aggregate layer with recycled
concrete and 10% replacement of the sand layer with crushed glass. The possible leaching
from these waste-stream materials is discussed in the remainder of this section.
Concurrent research by a colleague examined the use of waste-stream materials in
a Porous Landscape Detention (PLD) application, another type of stormwater BMP
(Kocman, 2008). A PLD consists of a layer of a peat/sand mixture atop a coarse
aggregregate layer and is typically vegetated. This collegues research included a
comprehensive screening of waste materials to replace each of the virgin materials in a
PLD.The criteria for testing the materials included flow rates, leaching, availability and cost.
This testing, as applicable to the waste-stream materials installed in the pervious concrete
test section, is discussed in the remainder of this section.
The first criteria examined the availability and cost of each of the waste-stream
materials in comparison with the virgin materials, and is summarized in Table 3.4.
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Table 3.4 Waste-Stream Material Cost and Availability Comparison (Kocman, 2008)
Material Availability Cost ($/ton material) Density (cy/ton material) Cost ($/cy)
Sand (Pioneer) Pass 22.95 .75 cy/ton $17.21
Glass (donated by Coors) Fail NA Unknown NA
V* aggregate (Pioneer) Pass $33.95 .75 cy/ton $25.46
Crushed concrete (Oxford Recycling) Pass $7.50 .67 cy/ton $11.19
Crushed glass failed to meet the availability criteria as a source of surplus crushed
glass is not readily available in the Denver metropolitan area. However, as this material
was donated from Rocky Mountain Bottling Company, a significant cost savings was
realized when compared with sand. Recycled concrete is readily available and is less than
half the cost of virgin aggregate. This reduction in material cost amounts to a significant
cost savings.
The next criteria examined the resulting water pollutants from 48-hours of contact
time with each waste material. Seven batches of media were added to individual
containers with distilled water filled to the top of the media. After 48 hours, the leachate
was drained and samples were sent to an analytical laboratory for analysis. This
experimental design was considered extreme as the drain time of the PCP system is
significantly less than 48 hours. The results of the leaching testing for the materials utilized
in the PCP test section as compared to Environmental Protection Agencys freshwater
standards are listed below in Table 3.5. None of the mixtures tested met all of the
freshwater standards.
39


Table 3.5 48-Hour Lechate Batch Test Results (Kocman, 2008)
POLLUTANT
MEDIA pH Nutrients (mg/L) Total Metals (ug/L)
z i- N03+No2 Total P Cad 3 o Q CL c N
Freshwater Criteria 6.5-9 10 0.055 2 13 65 120
Crushed Glass 9.52 14 5.23 3.04 2.7 110 0 119
Recycled Concrete 12.17 3.2 3.66 2.37 0 34.3 33 0
1 Total Kjeldahl Nitrogen
Due to the highly basic result of the recycled concrete, additional testing was
completed to investigate the effect of further flushing of water through this media. For the
first seven flushes, distilled water was added to the top of the concrete and drained after 48
hours. Whereas, the final three flushes were considered continuous flow as clean water
flowed through the system for 10 minutes before a measurement was taken. The results
are provided in Table 3.6. As previously mentioned, the 48-hour contact methodology is
considered extreme. The continuous flow methodology more accurately represents the
functionality of the field system.
Table 3.6 Recycled Concrete pH Monitoring Through Multiple Flushes (Kocman, 2008)
Flush Methodology pH
1st Flush 48-hour Contact 12.61
4'" Flush 48-hour Contact 12.29
7tn Flush 48-hour Contact 12.43
8tn Flush Continuous Flow 11.13
10,n Flush Continuous Flow 11.53
40


This testing indicated that after 10 flushes of water the pH has decreased, but still
exceeds the freshwater criteria for Colorado. Additionally, there is a noticeable significant
drop in pH between the seventh and eighth flush. This is likely attributable to the change in
methodology.
The field installation of the pervious concrete test section utilized recycled concrete
to replace the entirety of the 8-inch (20.32 cm) coarse aggregate layer and crushed glass
to replace 10% of the 7-inch (17.78 cm) fine aggregate layer. Based on Kocmans
research, these waste-stream materials raise concerns with regard to pH and pollutant
concentrations. Therefore, a first flush simulation and stormwater sampling were
completed to evaluate the leaching of the field installed system. These results are
contained in Sections 7.3 and 7.4 respectively.
3.5 Pervious Concrete Admixtures
Chemical admixtures used in regular concrete are often used in the production of
pervious concrete mixtures as well. These admixtures, such as water-reducing admixtures,
set retarders, hydration stabilizing admixtures, viscosity modifying admixtures and air-
entraining agents are used to improve the properties of a well proportioned pervious
concrete mixture. Admixtures should be used in accordance with the manufacturers
instructions and recommendations.
3.5.1 Air-Entraining Admixture (AEA)
Air entraining admixture is a liquid admixture used to stabilize the air within the
concrete mixture during the mixing phase of concrete production. The entrained air
increases the resistance of the concrete paste to damage from freezing and thawing.
Determination of the proper dosage is achieved through laboratory trial batching. However,
41


the quantity of entrained air in pervious concrete cannot be directly measured or verified
using traditional concrete test methods.
Due to the typical temperature variations in Denver, freeze-thaw cycles are a
common phenomenon and therefore of heightened concern in the region. Consequently,
the laboratory testing phases of research included batch testing of pervious concrete
mixtures with AEA. The methodology for the freeze-thaw testing will be discussed in
Section 5.1.4 and testing results will be presented in Section 5.5.5 and Section 5.6.5.
3.5.2 Viscosity Modifying Admixture (VMA)
Viscosity modifying admixtures are gum-based products that improve the
cohesivity of the cement paste by suspending the cement particles. These admixtures are
typically used in underwater placements and for self consolidating concrete. Their use in
pervious concrete mixtures has been found to improve the consistency of the mixture
during installation. A VMA was used in the field placement.
3.5.3 Set Retarders
Set retarders are chemical admixtures used to extend the setting time of pervious
concrete so as to ensure sufficient delivery, placement, vibration and/or compaction time.
Set retarders are also commonly used in hot weather conditions. Pervious concrete
mixtures are stiff mixtures with low water content, and tend to stiffen up faster than higher
slump conventional concrete. Concrete producers may also use more potent retarders
such as hydration stabilizing admixtures (HSA) to prolong the period in which the mixture is
retained in a fresh condition, facilitating discharge, allowing for longer periods for
installation of pavements and preventing build-up in the mixer trucks. A hydration
42


stabilizing admixture was used in the field application to accommodate truck and
placement time.
3.6 Pervious Concrete Cleaning and Maintenance
Removing debris and sediment from the surface of the pervious concrete
pavement is important for maintaining the porosity. The use of a power washer or street
sweeper is recommended to periodically clean the PCP surface (Tennis et.al., 2004). The
use of chemicals to clean pervious concrete pavements is not recommended.
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4. Background: Pervious Concrete Pavement in Denver, Colorado
The majority of PCP research to date has been completed in humid environments.
A minimal amount of construction and even less research has been completed in semi-arid
regions such as Denver, CO. Additionally, the frequent and regular occurrence of freezing
and thawing makes Denver a truly unique climate. The following sections contain
information on each of the known applications of pervious concrete in the Denver
metropolitan region, selected photographs, and commentary on the current condition of
these pavements. Appendix B provides a comprehensive photographic documentation of
the condition of the pavement at each of these sites.
A number of these locations have experienced failures of the wearing surfaces.
This deterioration triggered UDFCD to issue a temporary moratorium on pervious concrete
pavement in the Denver metropolitan area. Appendix C contains this moratorium. These
failures and the subsequent moratorium demonstrate the need for research into pervious
concrete design in the Denver metropolitan region and justify the work included in this
dissertation. UDFCD recognized the importance of this research study and provided a
letter of endorsement for this research, contained in Appendix D. Additionally, the UDFCD
contracted an independent investigation into the failure of PCP, the results of which are
summarized at the conclusion of this chapter.
4.1 Colorado Hardscapes (2004)
Colorado Hardscapes installed two sections of pervious concrete in December
2004. Each of these sections utilized different sized aggregate. The first section of
pervious concrete, shown in Figure 4.1, encompasses two parking stalls and consists of
44


the larger, 3/4-inch (1.905 cm) sized coarse aggregate. This section of PCP does not
show any structural deterioration at this point in time, as shown in Figure 4.2. It is worth
noting that the snow removed during plowing operations at this site is deposited on the
PCP near the curb edge. As a result, greater amount of sediment is apparent at this edge
and infiltration rate times recorded were slower than those in the center of the parking
stalls.
Figure 4.1 Pervious Concrete Pavement at Colorado Hardscapes
45


Figure 4.2 Pervious Concrete Pavement at Colorado Hardscapes (Typical Condition)
The second section of pervious concrete at Colorado Hardscapes consists of six
parking stalls, which utilized a number of different mixture designs and/or placement
techniques. The smaller, 3/8-inch (0.9525 cm) rock was used as the coarse aggregate in
all of these parking stalls. This second section of pervious concrete is shown in Figure 4.3.
The typical condition of this second section of PCP is shown in Figure 4.4. The pervious
concrete at this location is in good condition as it does not show any structural deterioration
at this time. The surface of some of these parking stalls are partially sealed, as shown in
Figure 4.5, resulting from the use of a vibratory screed rather than a roller screed (Buteyn
2009).
46


Figure 4.3 Pervious Concrete Pavement at Colorado Hardscapes
Figure 4.4 Typical Condition of PCP at Colorado Hardscapes
47


Figure 4.5 Pervious Concrete Pavement at Colorado Hardscapes (Surface Sealing)
4.2 Safeway Grocery Store (2005)
The pervious concrete parking lot at the Safeway Grocery Store on the northeast
corner of 13th Avenue and Krameria Street in Denver, Colorado was constructed in 2005.
The entire parking lot was placed using pervious concrete as shown in Figure 4.6. The
smaller, 3/8-inch (0.9525 cm) rock was used as the coarse aggregate in the PCP mixture.
A photograph of the PCP pavement condition at this location in April, 2005, shown
in Figure 4.7, does not show any significant signs of distress. Observations from
November, 2006, found no evidence of raveling, but some of the panels furthest away from
the store entrance had cracks between the widely spaced joints (Delatte, et al. 2007).
However, by June, 2008, this pervious concrete had deteriorated to the point that usability
was impaired, with the primary damage being surface raveling. This pervious concrete
parking lot was replaced with an asphalt pavement in 2008.
48


Weather conditions at the time of placement are one of the suspected causes of
the deterioration at this site. This pervious concrete was placed during the winter months
with snow on the ground. Additionally, the thermal blankets blew off of the concrete
prematurely. It is believed that the concrete did not hydrate properly. Furthermore, it is
suspected that the pervious concrete froze during the curing process. Additionally, steel
tipped snow plows were used to clear snow from the parking lot (Rottman 2008). These
are all possible contributors to the failure of the PCP at this location.
Figure 4.6 Photograph of Pervious Concrete at Safeway April 2005,
courtesy of Ben Urbonas (UWRI)
49


Figure 4.7 Photograph of Pervious Concrete at Safeway April 2005,
courtesy of Ben Urbonas (UWRI)
4.3 City of Lakewood Maintenance Facility (2005)
The demonstration site monitored by UDFCD at the Lakewood City Maintenance
Facility (constructed by UDFCD in 2005) has not exhibited any structural deterioration to
date. The pervious concrete section of this parking lot consists of twelve parking stalls with
the remaining portion of the lot comprised of asphalt. The PCP section of the City of
Lakewood parking lot contains two separate sub-sections of pervious concrete, each sub-
section consisting of six parking stalls. One sub-section uses the smaller, 3/8-inch (0.9525
cm) rock as the coarse aggregate in the PCP mixture. The other sub-section uses the
larger, 3/4-inch (1.905 cm) rock as the coarse aggregate. The plan view of the parking lot
and the pervious concrete tributary catchment area is shown in Figure 4.8. Figure 4.9 is a
general photograph of this site. Figure 4.10 shows the interface between the two sub-
sections of pervious concrete to demonstrate the different sizes of coarse aggregate used
50


in each. Photographs of the typical condition of the pervious concrete at this site for both
the large coarse aggregate and the small coarse aggregate sub-sections are contained in
Figure 4.11 and Figure 4.12, respectively.
Tributary Catchment To Porous Pavement
MONITORING IQUIPMfcNT
LEGEND
Watershed Boundary
Watershed Area in square feet
Porous Pavement ASTII 33 Sand
Technical Shack
Pressure Transducer
Samplers
PP-C is 100* Impervious
PP-T is 78.2* Impervious
Figure 4.8 City of Lakewood Pervious Concrete Parking Lot and Tributary Catchment
(Cheng 2008)
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Penny
(for scale)
3/8 Coarse Aggregate
Pervious Concrete
3/4 Coarse Aggregate
Pervious Concrete
Figure 4.10 Pervious Concrete Pavement at City of Lakewood Maintenance Facility
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Figure 4.11 Typical Condition of Large Coarse Aggregate PCP Sub-Section at
City of Lakewood Maintenance Facility
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4.4 Wal-Mart Super Center (2006)
A portion of the parking lot at the Wal-Mart Supercenter on the northwest corner of
Tower Road and Interstate 70 was constructed using pervious concrete in 2006. This
particular Wal-Mart is an experimental site in that it utilizes a variety of techniques for
reducing energy and environmental impacts. The parking lot at this experimental Wal-Mart
Supercenter contains a variety of pavement materials including, standard asphalt, standard
concrete, porous asphalt, pervious concrete and standard concrete pavement with radiant
heat. The pervious concrete pavement is used for a section of the parking lot pavement
some distance away from the store. The smaller, 3/8-inch (0.9525 cm) rock was used as
the coarse aggregate in the mixture design. Figure 4.13 is an aerial photograph of the Wal-
Mart parking lot, identifying the pervious concrete section. Figure 4.14 is a photograph of
the PCP section in relation to the store location.
Observations from November, 2006 recorded no visual evidence of cracking or
clogging (Delatte, et al. 2007). Figure 4.15 contains a photograph of the typical condition of
the pervious concrete today. As shown in Figure 4.15, deterioration of the pervious
concrete is minimal at this time, but similar to the Safeway site in 2007. As shown in Figure
4.16, there is a large pothole at the edge of the PCP section in the right wheel path in the
main driving path of the parking lot.
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Figure 4.13 Parking Lot of Wal-Mart Super Center.
Pervious concrete section of parking lot is circled in red.
(Colorado Association of Floodplain Managers n.d.)
Figure 4.14 Pervious Concrete section of Wal-Mart Parking Lot
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Figure 4.15 Typical Condition of PCP at Wal-Mart Parking Lot
Figure 4.16 Pothole in Pervious Concrete in Main Aisle of Wal-Mart Parking Lot
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4.5 Bestway Concrete (2006)
Bestway Concrete constructed a test slab at their Milliken, Colorado, plant location
in 2006. The smaller, 3/8-inch (0.9525 cm) rock was used as the coarse aggregate for this
test slab. This PCP is not subjected to vehicular loadings and does not show any signs of
deterioration at this time.
The Bestway Concrete ready mixed plant in Denver, Colorado has two strips of
pervious concrete. These two pervious concrete sections each provide for parking and are
separated by a standard concrete aisle, as shown in Figure 4.17. The first section, colored
green, is located near the plant office and is shown in Figure 4.18. The other section is at
the edge of the parking lot, near the fence, consists of eight parking spaces, and is shown
in Figure 4.19. The smaller, 3/8-inch (0.9525 cm) rock was used as the coarse aggregate
for both pervious concrete sections. This parking lot is subjected to daily vehicular loading
and the occasional heavy loadings of concrete trucks.
Observations from November, 2006 did not indicate any signs of deterioration but
did note slow drain times, indicating the possibility that the surface may have been sealed
during construction (Delatte, et al. 2007). Currently, this parking lot does not show any
structural deterioration. However, it is visually apparent that this location is severely
clogged, as shown in Figure 4.18 and Figure 4.19.
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Figure 4.17 Pervious Concrete at Bestway Concrete, Denver
Figure 4.18 Typical Condition of PCP Section Near Office of Bestway Concrete, Denver
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Figure 4.19 Typical Condition of PCP Section Near Fence of Bestway Concrete, Denver
4.6 Vitamin Cottage (2007)
The pervious concrete parking lot at the Vitamin Cottage on the northwest corner
of Colorado Boulevard and Evans Avenue in Denver, Colorado was constructed in 2007.
As shown in Figure 4.20, the Vitamin Cottage is on the corner of an outdoor shopping area
and the pervious concrete is located on the north and east sides of the store. The smaller,
3/8-inch (0.9525 cm) rock was used as the coarse aggregate in the PCP mixture. The
condition of the PCP at this location is quite variable. In general, the PCP on the north side
of the store is in good condition, as shown in Figure 4.21. However, the PCP on the east
side of the store is raveling and has deteriorated to the point that usability is impaired, as
shown in Figure 4.22 and Figure 4.23. Additionally, surface sealing is evident at a number
of locations in this parking lot, as shown in Figure 4.24.
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60


Figure 4.22 Typical Poor Condition of Pervious Concrete on East side of Vitamin Cottage
Figure 4.23 Extreme Condition of Pervious Concrete on East side of Vitamin Cottage
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Figure 4.24 Surface sealing of Pervious Concrete at Vitamin Cottage
4.7 Auraria Campus of the University of Colorado at Denver Parking Lot K (2008)
As part of this research, a pervious concrete test section was constructed in
Parking Lot K on the Auraria Campus of the University of Colorado Denver in July, 2008.
This test section consists of six parking stalls of pervious concrete. The remainder of the
parking area remains paved in six inches of standard asphalt pavement. Figure 4.25
contains a photograph of this pervious concrete test section. This pervious concrete
installation and performance are discussed in detail in Chapters 6, 7 and 8. As shown in
Figure 4.26, this pervious concrete is performing well as it does not show any structural
deterioration at this time.
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Figure 4.25 Pervious Concrete Pavement in Parking Lot K on the Auraria Campus of the
University of Colorado at Denver
Figure 4.26 Typical Condition of PCP Test Section in Parking Lot K on the
Auraria Campus of the University of Colorado at Denver
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4.8 UDFCD Moratorium
On June 4, 2008, The Urban Drainage and Flood Control District issued a
temporary moratorium on Porous Concrete Pavement in the Denver Metropolitan area due
to partial failures of the wearing surfaces. This moratorium is included in Appendix C.
Sites noted in the UDFCD PCP Moratorium Notification as having experienced
rapid deterioration of the porous concrete wearing surface include:
Safeway Grocery Store, SE corner of 13th Avenue and Krameria Street, Denver,
constructed in 2005. Deterioration to the point that usability is impaired.
Vitamin Cottage, NW corner of Colorado Blvd. and Evans Avenue, Denver,
constructed in 2007. Deterioration to the point that usability is impaired.
Wal-Mart Super Center, NW corner Tower Road and Interstate 70, Denver,
constructed in 2006. Deterioration minimal at this time, but similar to the Safeway
site in 2007.
The moratorium included a list of the suspected causes for the failures. This list
included chemical interaction with magnesium chloride, mechanical shearing and/or
abrasion by torsional motion of tires, freeze/thaw conditions, improper concrete mixture
design, placement and/or curing techniques.
These failures and the subsequent moratorium demonstrate the need for research
into pervious concrete design in the Denver metropolitan region and justify the work
included in this dissertation. Additionally, UDFCD commissioned a local materials testing
firm to complete an investigation into the pervious concrete failures documented. A
summary of this investigation is included in the following section.
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4.9 CTL Thompson Materials Investigation
In February, 2008, UDFCD contracted CTL Thompson Materials Engineers, Inc. to
investigate pervious concrete surface raveling failures in the greater Denver metropolitan
region. The scope of services included field observations, sample collection, laboratory
testing, analysis and a report. This report is available from UDFCD and is summarized in
the remainder of this section.
Four of the aforementioned sites, each displaying various stages of distress, were
selected by UDFCD for investigation. Locations remained ambiguous as the sites were
referenced as A, B, C and D. One of these sites was not displaying significant
distress or deterioration at the time of the investigation and was used as a control site. The
remaining three sites were displaying varying stages of deterioration.
Visual observations and photos were taken at each of the sites. Sample sections
were removed from each of the sites for laboratory testing. This testing included
measurements of the pavement thickness and surface erosion, compressive strength, unit
weight, void analysis, drainage analysis, chemical analysis, freeze-thaw durability and
petrographic analysis.
The investigation indicated several possible factors that may likely influence the
performance of pervious concrete, including:
Variation in compressive strength Data indicated relatively higher compressive
strengths for the non-distressed areas in the three problematic parking lots.
Larger aggregate size Mixture design information was not provided to the
material investigation consultant. However, data indicates that the non-distressed
control site was constructed with a larger aggregate mixture. Sites B, C and D
were constructed with smaller aggregate mixes and experienced surface
deterioration.
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Maintaining uniformity in void content Data indicated that the measured void
space in the samples for each site was inconsistent, likely indicating
constructability issues.
Permeability Drain time results of the constructed pavements exhibited
significant variability. As expected, the larger aggregate size mixture (Site A)
exhibited the fastest (best) drainage performance. Site D, which was identified to
have consolidation of the material in the bottom of the pavement, exhibited slowest
(poorest) drainage. Results indicated that permeability of the pervious concrete is
critical.
Chlorides Varying amounts of chloride were found in each of the sites. Deicing
salts (e.g., chloride) in the pavement material are deleterious to concrete and will
accelerate deterioration due to freeze-thaw cycling.
Freeze-Thaw Durability Samples from all four sites exhibited short-term complete
failure during freeze-thaw testing. Abrasion durability testing (excluding the freeze-
thaw conditioning) demonstrated less than 0.5% loss of the sample for the testing
cycle.
Maintaining drainage of the pavement system and not allowing the material to
become saturated from surface water appears to be the primary influence factor
associated with the lack of performance at the sites included in the investigation.
As a result of this investigation, the UDFCD is seeking solutions from the ready
mixed concrete industry to address the performance issues. The moratorium on pervious
concrete will remain in place until the industry has provided such solutions. To date, the
UDFCD moratorium on pervious concrete is still in place in the Denver metropolitan region.
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5. Laboratory Testing of Pervious Concrete Pavement
The main goal of the laboratory testing of the pervious concrete was to
determine an optimal mixture design to be utilized in the field installation and to
develop recommendations. For the purposes of this research, the criteria for the
pervious concrete design are threefold; structural, hydraulic, and incorporation of
waste-stream materials.
Structurally, the pervious concrete must be able to withstand vehicular
loading characteristic to parking lots. The Colorado Department of Transportation
(CDOT) provides compressive strength requirements for different classes of
standard concrete mixtures for a variety of uses. A CDOT Class P mixture,
typically used for pavements and curbs, requires a compressive strength of 4200
psi (28,958 kPa) at 28 days of age. A CDOT Class B mixture, used typically for
sidewalks and driveways, requires a compressive strength of 3000 psi (20,684
kPa) at 28 days of age. For the purposes of this research, a 28-day compressive
strength of 2000 psi (13,790 kPa) was considered acceptable for the pervious
concrete mixture.
This structural requirement is conservative in that the mixtures specified by
CDOT are designed for use by heavy vehicles such as busses and semi-trailers in
addition to standard passenger vehicles. However, the PCP field installation is only
subjected to standard passenger vehicles, as heavy vehicles are not permitted in
this parking lot. The weight of the vehicle is distributed to the four tires which
distribute the weight over the contact area with the pavement, the tire footprint.
The size of the tire footprint is determined by a number of factors including the
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make/model of the tire, and the level of inflation. The Guide for Mechanistic-
Empirical Design of New and Rehabilitated Pavement Structures specifies a
default tire contact area of 37.5 in2 (242 cm2) (ARA, Inc., 2004). In pavement
design, the contact pressure, exerted on the pavement by the tires on the vehicle,
is generally assumed to be equal to the tire pressure and is distributed evenly
across the tire footprint. (Huang, 2004). As an extreme example, consider a
vehicle with a weight of 20,000 lbs. (9,071.85 kg). Using the default tire contact of
37.5 in2 (242 cm2), this results in 133.3 psi (919.3 kPa) of contact pressure. Even
when subjected to such a massive vehicle the structural performance criteria of
2000 psi (13,789 kPa) is still a factor of 15 greater, providing more than sufficient
strength for the intended application.
Additionally, the pervious concrete needs to have the hydraulic capability
to support the stormwater runoff at the site. Typically, between 15% and 25% voids
are achieved in the hardened pervious concrete, resulting in flow rates on the
order of 480 in/hr (1219 cm/hr) (Tennis, et al. 2004). As will be discussed further,
the porosity testing methodology, as presented in Section 5.1.3 is known to
provide an under-estimate of the actual porosity. With this in mind, 10% porous
void space was considered acceptable for the purposes of this research.
Finally, this study seeks to maximize the incorporation of waste-stream
materials without sacrifice to the structural or hydraulic capacities of the pervious
concrete.
Currently, members of ASTM Subcommittee C9.49 are attempting to standardize
the testing methods for pervious concrete as methodologies are not well established.
When it formed in the summer of 2007, subcommittee leaders established five work groups
to examine five different areas of pervious concrete testing: field permeability, compressive
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strength, flexural strength, fresh concrete density, and voids content and hardened
concrete density and porosity.
As laboratory testing methodologies are not well established for pervious concrete,
standardized testing procedures for standard concrete were modified so as to be
applicable for pervious concrete. Section 5.1 contains the procedures developed and used
in this study. Sections 5.2 through 5.6 contain the results of the laboratory testing
completed through six phases of research.
5.1 Laboratory Testing Methodology
5.1.1 Cylinder Compression Testing Methodology
ASTM C 39 [2005] covers the testing procedures for the determination of
compressive strength of cylindrical concrete specimens such as molded cylinders and
drilled cores. This test method consists of applying a compressive axial load to molded
cylinders or cores at a rate which is within a specified range of 35 +/- 7 psi/s [0.25 +/- 0.05
MPa/s] until failure occurs. The compressive strength of the specimen is calculated by
dividing the maximum load attained during the test by the cross-sectional area of the
specimen.
ASTM C 39 [2005] is limited to concrete having a unit weight in excess of 50 pcf
(800.9 kg/m3). Unit weights of pervious concrete mixtures are approximately 70% of
traditional concrete mixtures (100 125 pcf, 1602 2002 kg/m3) (Tennis, et al. 2004).
While the unit weight of pervious concrete is well within the limitations of ASTM C 39
[2005], there are a number of difficulties in using this methodology for pervious concrete.
The ASTM Subcommittee C9.49 compressive strength task group is attempting to develop
a standardized compressive strength test for pervious concrete. The procedure is difficult
69


because of the challenges of standardizing consolidation techniques, capping material, and
choosing an appropriate cylinder size. Without established testing techniques, the following
procedures were developed for the compressive strength testing of pervious concrete
completed for this research.
Procedure:
1. Place concrete into a 4-inch (10.16 cm) diameter x 8-inch (20.32 cm) height
cylinder in a series of three lifts, rodding and compacting between lifts. Each lift
should be rodded 25 times, and the handle of a standard sledge hammer is used
to tap the surface approximately 25 times to achieve compaction.
2. Immediately cover with 6 mil (0.006 in, 0.1524 mm) thick plastic and adhere the
plastic to the cylinder mold.
3. Place the cylinder into the concrete curing room with the temperature fixed at 73
3F [23 2C],
4. After 10 days, remove the plastic sheathing from the concrete.
5. At the specified time (typically 28 or 56-days of age), remove the concrete cylinder
from the concrete curing room, and remove the concrete from the cylinder.
6. Saw cut the ends of the cylinders to create flat uniform surfaces.
7. Measure the diameter and the length of the specimen.
8. Complete porosity testing (or any other testing that needs to be completed on the
specimen).
9. Place neoprene pads confined by steel end caps on either end of the specimen.
Note: Sulfur capping is alternative method to cap samples. However, for
consistency the same capping method, neoprene pads, was utilized throughout
laboratory testing phases of this research.
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10. Place the concrete specimen into the compressive testing machine.
11. Zero the compressive testing machine
12. Use the metered advance mode and slowly apply load until the specimen breaks.
As pervious concrete has a lower compressive strength than standard concrete,
and this strength is largely unknown, a loading rate approximately half of that used
in ASTM C 39 [2005] (17.5 +/- 7 psi/s [0.125 +/- 0.05 MPa/s]) is recommended for
pervious concrete.
13. Calculate the compressive strength per the calculation in ASTM C 39 [2005].
Literature reports that pervious concrete mixtures can develop compressive strengths
in the range of 500 to 4000 psi (3.5 MPa to 28 MPa), which is suitable for a wide range of
applications. Typical values are about 2500 psi (17 MPa). As with any concrete, the
properties and combinations of specific materials, as well as placement techniques and
environmental conditions, will dictate the actual in-situ strength.
However, conventional cast cylinder strength tests are of little value because the field
consolidation of pervious concrete is difficult to reproduce in cylindrical test specimens.
Additionally, confinement due to the sides of the cylinder molds results in increased void
content along these edges, and as strengths are heavily dependent on the void content,
this can noticeably lessen the compressive strength of cast cylinder samples. Drilled cores
are the best measure of in-place strengths, as compaction differences make cast cylinders
less representative of field concrete.
5.1.2 Core Compression Testing Methodology
Drilled cores are the best measure of in-place strengths (Tennis, et al. 2004).
Phase I of Laboratory Testing examined the differences in compressive strengths from
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cylinders and cores. The compressive testing of core samples is procedurally identical to
the compressive testing of cylinders. The differences in procedures reside in the
methodology of obtaining and preparing the sample for testing.
For the purposes of core compression testing in the laboratory, a 10-inch x 10-inch
x 7-inch (25.4 cm x 25.4 cm x 17.78 cm) test block was created for each of the pervious
concrete mixtures. A core drill mounting platform, shown in Figure 5.1, was designed and
constructed that facilitated the removal of four specimens from each of the testing blocks.
Figure 5.1 Test Block Core Drill Mounting Platform
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Procedure:
1. Construct one 10-inch x 10-inch x 7-inch (25.4 cm x 25.4 cm x 17.78 cm) test block
form for each of the testing blocks.
2. Place the pervious concrete into the forms in a series of four lifts, compacting
between lifts. Each lift should be rodded 50 times. A piece of plywood should be
cut to fit just inside the framework of the testing block. Place plastic sheathing
between the concrete and this piece of plywood. Use a sledge hammer is used to
tap the surface approximately 25 times to achieve compaction.
3. Cover the pervious concrete with 6 mil thick (0.006 in, 0.1524 mm) plastic
sheathing and securely attach the plastic to the test block form.
4. Place the in the concrete curing room.
5. Allow the concrete to cure for 10 days prior to removing the plastic sheathing.
6. At the specified time (typically 28 or 56-days of age) remove the concrete cores
from the testing blocks.
7. Test for compressive strength using the procedures outlined in Section 5.1.1.
While the strength of conventional concrete is determined by its w/cm, pervious concretes
strength is controlled by both the w/cm and unit weight (Malhotra, 1976). The load path
through pervious concrete is through the paste, and the paste is assumed to be weaker
than the aggregates.
5.1.3 Porosity Testing Methodology
The porosity testing group of the ASTM Subcommittee C9.49 is in the midst of
evaluating historical information based on a field test developed by staff at the University of
South Carolina and ASTM C 140 [2007] as possible methodologies for evaluating the
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porosity of pervious concrete pavements. However, the group has yet to determine
appropriate testing methodologies for determining the porosity of pervious concrete.
Therefore, for the purposes of this research a volume displacement method was used to
determine the percentage of porous void space. The advantage of this method is that it
only accounts for the porous void space open for water to flow through the pervious
concrete matrix. Porous air pockets are not included. An additional advantage of this
methodology is that it is not complicated nor time consuming. However, one must be aware
that this method provides an under-estimate of the total porosity. This methodology can
either be used on cylinders or cores removed from the test blocks.
Procedure:
1. Obtain a container that can completely contain the concrete specimen (it is
preferable, if possible, to use a container with the same dimensions as the
concrete specimen, i.e., for concrete cylinder specimens use an empty cylinder
mold). Measure the inside dimensions of the container (if not readily available).
2. Measure the diameter and length of the pervious concrete.
3. Place the pervious concrete specimen into the container.
4. Slowly pour water into the container until it is filled. As the water nears the
capacity of the container, the flow should be limited to a trickle. Once the water
over-flows the container, the water flow should be limited to a drip. Continue to drip
water for an additional approximate 15 seconds after over-flowing the container.
5. Pour the water from the container into a graduated cylinder, and measure the
amount of water. The container should be allowed to drain until no water drips from
the container for a period of at least 15 seconds.
Note: The longer that the sample is submerged in the water filled container, more
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of the smaller inner voids of the pervious concrete will become saturated, thus
increasing the percentage of porous void space calculated and providing a more
accurate measurement of the porosity.
6. Calculate the percent porous void space as:
Volume nf Water
% Porous Void Space = ----------------------
Volume of Concrete Specimen
(Equation 5.1)
During porosity testing, water is poured into a container holding the pervious
concrete sample and then immediately transferred to a graduated cylinder for
measurement. This methodology provides an under-estimate of the porous void space as
the water is not allowed to sit in the container for an extended time and migrate into the
smaller inner void spaces within the specimen. Nor is extended time allotted to drain the
water from the sample into the graduated cylinder.
5.1.4 Freeze-Thaw Testing Methodology
ASTM C 666 [2003] freeze-thaw testing for concrete is a necessary durability test
for regions that experience such temperature cycles. Colorado is classified as S, or a
severe weathering region in ASTM C 33 [2007] with special note that regions located
above 1600m (5,000ft) in elevation should consider higher, self-imposed requirements for
concrete performance. The ACI 318 [2005] requirements for freeze-thaw are limited to a
low w/cm and total air content of 0.45 and 6% (nominal aggregate size 1.9 cm as used in
these mixtures), respectively, and do not consider the incorporation of fly ash as
significant. Although the resistance to freezing-and-thawing is primarily a function of the air
entrainment [Malhotra and Mehta, 1999], fly ash does reduce the w/cm and lowers the
permeability of concrete, providing some benefit.
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There are two different procedures specified in ASTM C 666 [2003]. Procedure A,
rapid freezing and thawing in water, and Procedure B, rapid freezing in air and thawing in
water. Both procedures are intended for use in determining the effects of variations in the
properties of concrete on the resistance of the concrete to the freezing-and-thawing cycles
specified in the particular procedure. Neither procedure is intended to provide a
quantitative measure of the length of service that may be expected from a specific type of
concrete. For either procedure, the requirements for ASTM C 666 [2003] are to evaluate
the transverse frequency of the mortar bars every 42 cycles (4 cycles per day) and
calculate the Relative Dynamic Modulus of Elasticity (RDME) for each sample. This is a
ratio of the loss of transverse frequency from the initial measurement, and testing is
completed at 300 freeze-thaw cycles or when RDME reaches a minimum of 60% of the
initial, whichever comes first. The durability factor (DF) is the reported RDME multiplied by
the number of cycles at which RDME reaches 60% of initial. Or, when the RDME reaches
300 cycles before decreasing to 60% of initial, the final RDME at 300 cycles is reported as
the DF.
However, due to the porous nature of pervious concrete, the transverse frequency,
which is used to calculate the RDME, cannot be measured accurately. Thus, a modified
procedure needed to be developed to measure the condition of the pervious concrete
mortar bars subjected to freeze/thaw cycling. As the pervious concrete deteriorates due to
freeze-thaw deterioration, the cement paste bond between adjacent aggregate particles is
broken. If all of the cementitious bonds surrounding a single aggregate break, then this
aggregate particle becomes separated from the specimen. A group of aggregates may
experience the same phenomenon wherein all of the bonds surrounding a cluster of
aggregates break, separating the cluster from the specimen. As these aggregates break
loose there is a corresponding measurable mass loss to the specimen. The exception
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being if the separation occurs within the body of the sample. It was decided to use mass-
loss as a measure of the deterioration of the pervious concrete mortar bars subjected to
freezing and thawing cycling. While multiple studies have examined both the RDME and
the mass-loss of samples, there is no established correlation between the two. In fact, the
calculation of the RDME is based on the assumption that the mass of the specimen
remains constant throughout the duration of the test, as noted in Note 9 of ASTM C666
[2003]. As will be discussed in Sections 5.2 through 5.4, the freeze-thaw testing of the
pervious concrete specimens was difficult (Phases I and II of testing). After some trial and
error, the following testing procedure was developed.
Procedure:
1. Concrete Freeze-Thaw Molds and Compaction
a. Spray Freeze-Thaw molds with a form breaker (such as WD-40).
b. Place pervious concrete mixture into Freeze-Thaw molds in two lifts,
compacting the concrete between lifts.
2. Cover the pervious concrete with 6 mil (0.006 in, 0.1524 mm) plastic sheathing and
securely attach the plastic to the freeze-thaw forms. Place the covered freeze-thaw
molds into the concrete curing room.
3. After 10 days, remove the plastic from the freeze-thaw molds. Remove the
pervious concrete from the molds and place the concrete specimen in the curing
room.
4. 28-days after the initial placement (steps 1&2), remove the concrete specimen
from the concrete curing room.
5. Prepare the specimen to be placed into the Freeze-Thaw Chamber.
a. Measure the dry weight of the concrete specimen.
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b. Thoroughly soak the concrete specimen under running water, then pat the
surface dry and measure the surface dry weight of the concrete
specimen (this will serve as the starting point weight for the freeze-thaw
specimen).
c. Remove an empty tray from the freeze-thaw chamber. (Clean the tray if
necessary.)
d. Place a z shaped spacer bar into the tray. This will hold the sample off of
the bottom of the freeze-thaw tray.
e. Place the concrete specimen into the tray.
f. Place the tray into the freeze-thaw chamber.
g. Ensure that the side bars have good contact with the tray.
h. Use 2 clips per side to attach the tray to the adjacent trays.
i. Fill the tray with water and close the freeze-thaw chamber.
Note on the freeze-thaw disc, the date and time that the specimens were
placed into the freeze-thaw chamber.
The freezing-and-thawing cycle for both procedures ofASTM C666 [2003]
consist of varying the temperature of the samples between 0 to 40F (-18
to 4C). The freeze-thaw chamber was set to cycle through this
temperature range four times per day.
6. Remove the specimen (in its tray) from the freeze-thaw chamber every other day
(it is easiest to do this at maximum temperature).
7. Drain all water from the tray and remove any loose aggregate or small chunks.
8. Place the freeze-thaw beam into the curing tanks in the concrete curing room for
30 minutes.
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9. Remove the freeze-thaw beams from the curing tanks and drain water (also
remove any loose aggregate or chunks).
10. Rub the surfaces of the freeze-thaw beam to remove any loose aggregate. Pat the
surfaces of the freeze-thaw beam so that it is surface dry.
11. Weigh the specimen.
12. Place the z shaped spacer bar into the tray and return the freeze-thaw beam (in
its tray) to the freeze-thaw chamber. Ensure good contact with side bars, clip to
adjacent trays and fill the tray with water.
13. Continue measuring the mass of the freeze-thaw beam until the pervious concrete
has completely disintegrated.
Note that the porosity of pervious concrete from the large voids is distinctly different
from the microscopic air voids that provide protection to the paste in conventional concrete
in a freeze-thaw environment. When the large open voids are saturated, complete freezing
can cause severe damage in only a few cycles. Standardized testing by ASTM C 666
[2003] may not represent field conditions fairly, as the large open voids are kept saturated
in the test, and because the rate of freezing and thawing is rapid. It is expected that
pervious concrete will display better performance in the field because of the rapid draining
characteristics of the pervious concrete. Although complete saturation does not accurately
represent field conditions, this method allows all samples to be tested uniformly and
provide direct comparisons between mixtures. Furthermore, this freeze/thaw procedure
provides for the worst case scenario as water is forced to freeze within the pervious
concrete layer.
Research indicates that entrained air in the paste dramatically improves freeze-thaw
protection for pervious concrete. In addition to the use of air-entraining agents in the
cement paste, placing the pervious concrete on a minimum of 6-inches (15.24cm) of a
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drainable rock base, such as 1-inch (25-mm) crushed stone, is normally recommended in
freeze-thaw environments where any substantial moisture will be encountered during
freezing conditions. The Urban Drainage and Flood Control District recommends a
minimum of 8-inches (20.32 cm) of coarse aggregate and 7-inches (17.78 cm) of fine
aggregate (sand) beneath the pervious concrete. The coarse aggregate layer primarily
functions to store the water that has entered through the pervious concrete until it can be
filtered through the sand layer. As such, the water storage for a pervious concrete system
is designed to occur in the coarse aggregate layer and not in the pervious concrete itself,
thus minimizing the likelihood of freezing and thawing to actually occur in the pervious
concrete layer. Therefore, testing of the pervious concrete samples in the saturated
condition represents the worst-case scenario. In a field application, freezing and thawing
would only be occurring in the pervious concrete due to improper mixture or system design
or severe clogging. The testing procedure developed and used throughout the laboratory
testing phases of this research was based on Procedure A of ASTM C666 [2003] wherein
rapid freezing and thawing take place in water. Procedure B, rapid freezing in air and
thawing in water, is more representative of the freezing and thawing expected to occur in
the field.
5.2 Laboratory Testing Phase I
This phase of testing utilized the original literature review of more than 100
sources as the basis for the mixture design and placement procedures. A total of five
different mixtures were designed by simply eliminating the fine aggregate (sand) from a
typical standard concrete mixture design as is consistent with the no -fines mixture
design. The base mixture design contained 550 lb (249.47 kg) of ordinary Portland cement
(OPC) per cubic yard of concrete and had a w/cm of 0.30. This base mixture design was
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then modified with the addition of air-entraining admixture, or partial fly ash (Class F)
replacement for Portland cement. A list of each of the mixtures created during this phase of
testing is provided below, the mixture design specifications are provided in Appendix E.
1. Phase I Mixture 1 (100% OPC)
2. Phase I Mixture 2 (100% OPC with 2 fl oz / cwt AEA)
Note: cwt is a hundred weight" and is equivalent to exactly 100 pounds (45.36 kg)
of cement.
3. Phase I Mixture 3 (10% Class F fly ash replacement)
4. Phase I Mixture 4 (20% Class F fly ash replacement)
5. Phase I Mixture 5 (100% OPC with 1 fl oz / cwt AEA)
For each of the five mixtures the following testing samples were prepared:
4 compression cylinders each 4-inch (10.16 cm) x 8-inch (20.32 cm)
2 freeze-thaw beams each 3 inch x 4 inch x 16 inch (76mm x 102mm x 406mm)
1 10-inch x 10-inch x 7-inch (25.4 cm x 25.4 cm x 17.78 cm) sample block from
which core samples were taken.
5.2.1 Placement and Curing Procedures
Concrete was placed into formwork in a single lift, and the surface was toweled.
The pavement surface was allowed to air dry and was not covered with plastic. After two
days all concrete samples were moved to the concrete curing room.
During placement of Mixture 2 (100% OPC with 2 fl oz (59.15 cm3)/ cwt AEA), this
mixture appeared to have a wetter consistency than the other mixtures. Additionally, after
two days, this mixture appeared to be solid with 0% porosity, as shown in Figure 5.2.
Therefore, an additional air-entrainment mixture, Mixture 5, was created which used half as
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much air entrainment as did Mixture 2. Mixture 5 appeared to have noticeably improved
porosity characteristics when compared to Mixture 2.
o
Figure 5.2 Freeze-Thaw Beam for Phase I Mixture 2.
5.2.2 Testing Results
The samples were removed from the curing room for testing at 28-days of age.
The cylinders and cores were tested for compressive strength, and freeze/thaw testing
began.
The 28-day compressive strength testing results for the cylinders and the cores are
shown in Table 5.1. The average core compressive strength listed is the average
compressive strength of two cored samples. The average cylinder compressive strength is
the average compressive strength of two cylinder samples. The average compressive
strength is the average compressive strength of the two core and two cylinder samples.
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