Laboratory evaluation of polymer-modified pervious concrete (PMPC) / Baosha Huang, Xiang Shu, Hao Wu, Qiao Dong

GEORGIA DOT RESEARCH PROJECT 08-06 FINAL REPORT
LABORATORY EVALUATION OF POLYMER-MODIFIED PERVIOUS CONCRETE (PMPC)
OFFICE OF MATERIALS AND RESEARCH RESEARCH AND DEVELOPMENT BRANCH

LABORATORY EVALUATION OF POLYMER-MODIFIED PERVIOUS CONCRETE
(PMPC)
Prepared for Office of Materials and Research Georgia Department of Transportation
Baoshan Huang, Ph.D., P.E.
Xiang Shu, Ph.D. Hao Wu, Ph.D. Candidate Qiao Dong, Ph.D. Candidate Department of Civil and Environmental Engineering The University of Tennessee, Knoxville
August 2010

Technical Report Documentation Page

1. Report # FHWA-GA-10-0806

2. Government Accession #

3. Recipient's Catalog #

4. Title & Subtitle

5. Report Date

Laboratory Evaluation of Polymer-Modified Pervious Concrete (PMPC)

August 2010

7. Author(s) Baoshan Huang, Xiang Shu, Hao Wu, and Qiao Dong

6. Performing Organization Code

9. Performing Organization Name & Address
The University of Tennessee Depart of Civil and Environmental Engineering 223 Perkins Hall Knoxville, TN 37996 12. Sponsoring Agency Name & Address
Office of Materials and Research Georgia Department of Transportation 15 Kennedy Dr., Forest Park, GA, 30297-2534

8. Performing Organization Report # 08-06 10. Work Unit # (TRAIS)
11. Contract or Grant #
13. Type of Report & Period Covered Final; November 2008 August 2010

14. Sponsoring Agency Code

15. Supplementary Notes
16. Abstract High porosity with interconnected voids between aggregate particles in portland cement pervious concrete
(PCPC) causes a significant reduction in strength and abrasion resistance, which can be potentially improved through polymer modification. This study evaluates the laboratory performance of latex-modified pervious concrete with a focus on the abrasion and freeze-thaw resistance. Various laboratory tests were conducted to evaluate the physical properties (air voids, permeability), mechanical properties (compressive and split tensile strengths), and durability performance (abrasion and freeze-thaw resistance) of pervious concrete mixtures. The test results show that latex desirably improved the strength and abrasion resistance of PCPC, whereas fiber did not have a significant effect on the mechanical properties of PCPC. Even for pervious concrete, air-entraining admixture was helpful for improvement of freeze-thaw durability. A small field project validated the mix design obtained from the laboratory experiments. A relatively large field project is recommended to verify the abrasion and durability performance of pervious concrete pavements in future study.

17. Key Words
Pervious Concrete, Polymer Modification, Mix Design, Abrasion, Performance, Durability

18. Distribution Statement No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161

Security Classification (of this Security Classification (of this 21. # Of Pages

report)

page)

Unclassified

Unclassified

43

22. Price

Form DOT F 1700.7 (5-02)

Acknowledgements
We would like to thank the Georgia Department of Transportation (GDOT) for funding this research project. We would also like to acknowledge the Portland Cement Associate (PCA) to provide a graduate fellowship to augment the funding for the development of abrasion resistance testing procedures for pervious concrete. Thanks also go to the Tennessee Concrete Association and the Transit-Mix Concrete Company for help with the field project.
i

Table of Contents
EXECUTIVE SUMMARY................................................................................................ iv CHAPTER 1 INTRODUCTION ........................................................................................ 1
1.1 Background ............................................................................................................ 1 1.2 Objectives .............................................................................................................. 2 1.3 Scope of Study ....................................................................................................... 2 1.4 Literature Review................................................................................................... 3 CHAPTER 2 RESEARCH APPROACH ........................................................................... 5 2.1 Laboratory Experiment .......................................................................................... 5
2.1.1 Materials ...................................................................................................... 5 2.1.2 Mix Design................................................................................................... 5 2.1.3 Sample Preparation ...................................................................................... 6 2.1.4 Test Methods ................................................................................................ 7
2.1.4.1 Air Voids Test ..................................................................................... 7 2.1.4.2 Permeability Test................................................................................ 8 2.1.4.3 Compressive Strength Test................................................................. 9 2.1.4.4 Split Tensile Strength Test................................................................ 10 2.1.4.5 Cantabro Test ................................................................................... 10 2.1.4.6 APA Abrasion Test ............................................................................11 2.1.4.7 Sweep Abrasion Test ........................................................................ 12 2.1.4.8 Draindown Test ................................................................................ 13 2.1.4.9 Freeze-Thaw Test ............................................................................. 14 2.2 Field Project ......................................................................................................... 15 CHAPTER 3 EXPERIMENTAL RESULTS AND ANALYSIS....................................... 17 3.1 Air Voids Results.................................................................................................. 17 3.2 Permeability Results ............................................................................................ 19 3.3 Compressive Strength Results ............................................................................. 21 3.4 Split Tensile Strength Results .............................................................................. 23 3.5 Cantabro Test Results........................................................................................... 25
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3.6 APA Abrasion Results .......................................................................................... 28 3.7 Sweep Abrasion Test Results ............................................................................... 29 3.8 Draindown Test Results ....................................................................................... 30 3.9 Freeze-Thaw Test Results .................................................................................... 30 CHAPTER 4 CONCLUSIONS AND RECOMMENDATIONS...................................... 33 REFERENCES ................................................................................................................. 35
iii

EXECUTIVE SUMMARY
Portland cement pervious concrete (PCPC) has been increasingly used to reduce the amount of runoff water and improve the water quality near pavements and parking lots, but seldom used in highway pavement structures due to the reduced mechanical and durability performance associated with the high porosity. However, the performance of pervious concrete can be improved through polymer modification. The objectives of this study were to evaluate the behavior and performance of polymer-modified pervious concrete (PMPC) through laboratory testing and to assess the feasibility of using PMPC as a surface layer of pavements. The laboratory tests included physical property testing (air voids, permeability, and draindown tests), mechanical property testing (compressive and split tensile strength tests), and durability performance testing (Cantabro, APA abrasion, and sweep abrasion tests). A small-sized field project was also performed to verify the mix design from the laboratory experiments.
Based on the results from the laboratory tests, the major findings and recommendations can be summarized as follows:
Latex polymer could significantly improve the strength and abrasion resistance and slightly decrease the air voids and permeability of PCPC. Fiber had no significant effect on the mechanical properties and abrasion resistance of PCPC.
PCPC made with large size aggregate had weaker mechanical properties and abrasion resistance than the mixes made with small size aggregate, mainly due to the reduced contact area between adjacent aggregate particles.
Both the Cantabro and APA abrasion tests were effective for assessing the abrasion resistance of pervious concrete. The two parameters, weight loss and wear depth, could both be used as an indicator of abrasion resistance in the APA abrasion test.
The field mixtures validated the mix design obtained from the laboratory experiments. Even for pervious concrete, air-entraining admixture was helpful
iv

for improvement of freeze-thaw durability. Properly designed pervious concrete mixtures could meet the permeability,
strength, and durability requirements. The relatively optimum ranges of the properties of PCPC mixtures are 15-20% effective air voids, 1.0-2.0 mm/s permeability and 20-25 MPa compressive strength. These findings are based on the results from a laboratory study and a small-sized field project. A relatively large field project is recommended to verify the abrasion and durability performance of pervious concrete in future study.
v

CHAPTER 1 INTRODUCTION
1.1 Background
Pervious concrete (PC), or portland cement pervious concrete (PCPC), has been increasingly used to reduce the amount of runoff water and improve the water quality near pavements and parking lots. The open pore structure that allows high rates of water transmission is the key characteristic of pervious concrete. This pavement technology creates more efficient land use by eliminating the need for retention ponds, swales, and other stormwater management devices. The rapid drainage of water through interconnected voids can minimize wet weather spray, improve visibility, and minimize glare. However, due to the relatively low strength associated with high porosity, pervious concrete cannot be routinely used as load-bearing pavement surface without further treatments. The application of pervious concrete is limited to squares, footpaths, parking lots, and paths in parks (ACI 2006; Tennis et al. 2004; Montes 2006).
Polymer-modified concrete (PMC), or polymer portland cement concrete, is portland cement concrete modified with low dosage of polymer, typically 5% or less by weight of concrete. The polymer and the cement hydration products commingle and create two interpenetrating matrices, which work together, resulting in an improvement in the material properties of portland cement concrete (PCC) alone, such as improved strength and durability, and much better ductility.
Polymer-modified pervious concrete (PMPC) can be developed if pervious concrete is modified with low content of polymer, or polymer-modified concrete is produced with high porosity. The three-dimensional continuous films or membranes of polymer, intermingled with the hydrate cement paste, bind the cement hydrates and aggregate particles together. Limited studies in Europe showed that PMPC possesses highly increased strength, highly enhanced fatigue characteristics (fatigue life was increased by approximately one order of magnitude compared to conventional pervious concrete), and much better ductility. It also exhibits good noise absorption. Therefore,
1

there is a significant potential for PMPC to be used as pavement surface layer just as open graded friction course is used as a surface layer in asphalt pavements.
Until now, no systematic study has ever been done about the properties and application of PMPC in the United States. This research was conducted to investigate the mix design method of polymer-modified pervious concrete and to evaluate the performance of PMPC mixtures.
1.2 Objectives
The objectives of the research were to evaluate the behavior and performance of PMPC through laboratory testing and to assess the possibility of using PMPC as a surface layer of pavements. In this research, both the mechanical properties and durability of PMPC were considered.
1.3 Scope of Study
The scope of the research work included the following: z Three different coarse aggregate sizes (1/2 inch, 3/8 inch, No.4 size) will be considered in the mixtures to be evaluated. z One type of polymer will be selected and incorporated into the mixtures based on their performance and cost. The performance and properties of PMPC will be compared to those of the conventional pervious concrete without polymer. Latex is the most common polymer used in Portland cement concrete. It is a suspension of monomers or polymers in water and it is relatively simple to be incorporated into concrete. z Silica fume, fiber (tentatively polypropylene fiber), high range water reducing agent (HRWRA), and a small amount of natural sand will also be considered in the mix design to maximize the performance of PMPC. z The engineering performance tests in this study include the compressive strength test, the split tensile strength test, air voids test, permeability test, and the Cantabro test.
2

1.4 Literature Review
Portland cement pervious concrete (PCPC) is an open-graded friction course (OGFC) mixture with highly interconnected voids between aggregate particles. Due to the property of high porosity, a permeable structure could be created, which makes PCPC an environmentally friendly green material (Huang et al. 2010). However, in order to obtain high porosity and high water permeability, no or little fine aggregate could be added into the mixtures, which leads to the fact that in PCPC, aggregate particles are bonded together through aggregate to aggregate contacts rather than embedded in the continuous cement mortar matrix, as in ordinary portland cement concrete. Consequently, the bonding strength between adjacent aggregate particles of pervious concrete is relatively weak compared with that of ordinary concrete, which causes PCPC to be more vulnerable to spalling and raveling under moving traffic loads. Therefore, in addition to strength, the abrasion and raveling resistance is vital for the performance of PCPC as well. Due to the relatively reduced strength and abrasion resistance, most of PCPC is currently restricted to applications such as parking lots, sidewalks, pavement subbases, and surface layers of low traffic pavements (ACI 2006; Tennis et al. 2004; Montes 2006).
A number of studies show that the strength of PCPC can be improved by using smaller grain-size coarse aggregates, adding a few fine aggregates or some special chemical reinforcing agents (Yang and Jiang 2003). Some studies demonstrate that latex-modified mortars and concretes have much higher strength than conventional mortars and concretes. Ramakrishnan (1992) found that Styrene Butadiene Rubber SBR latex-modified concretes had an apparent increase in direct tension bonding strength compared with that of the unmodified concrete. Ohama (1995) also reported that mortars modified with SBR latex with a latex/cement ratio of 0.2 had an impact resistance about 10 times greater than that of unmodified mortars. Kevern (2008) found that addition of polymer significantly improved the strength and freeze-thaw resistance of PCPC mixtures, which enables pervious concrete to keep high strength while maintaining high porosity. In addition to latex polymer, fiber is another popular group that can be added into the mixtures to further enhance the mechanical properties of PCPC. It has been reported that well-distributed fibers in the mixtures have such benefits as inhibiting and controlling the
3

development of cracks in concrete, reinforcing against impact force and improving durability (Bayasi and Zeng 1993). However, findings from a study by Li et al. (2004) demonstrate that a small amount of polypropylene fiber (0.91 kg/m3 of total concrete) slightly decreases the compressive and shear strengths, although the toughness and flexural fracture resistance show an increase. Similar results were obtained by Alhozaimy et al. (1996).
Numerous testing methods and devices have been introduced in ASTM to evaluate the abrasion resistance of conventional concrete, such as ASTM C 779, C 418, C 1138, and E 303 (ASTM 2005a; 2006b,c; 2008). Furthermore, many other modified methods or testing machines similar to those mentioned above have also been established (Sadegzadeh and Kettle 1988; Dhir et al. 1991; Atis 2002). However, none of the methods for testing conventional concrete have been proven effectively for pervious concrete, because during the abrasion process of pervious concrete, the primary damage is the aggregate particles on the surface being worn off or crushed by impact and spalling from moving vehicles. Currently, a standard test for concrete abrasion resistance given in ASTM C 944 was introduced and modified by Kevern (2008) for pervious concrete through a rotating-cutter machine. Moreover, the Los Angeles abrasion machine, which is initially used for testing aggregates in ASTM C 131, has been recommended for testing the abrasion resistance of asphalt OGFC and porous friction course (PFC) (Watson et al. 2003; Alvarez et al. 2010). Based on the simulations of real situations on pavements, a cyclic testing system, the Asphalt Pavement Analyzer (APA), was also introduced at the University of Tennessee to evaluate abrasion resistance of PCPC. During the test, the specimens were subjected to repeated wheel loads with controllable magnitude and contact pressure, and both dry and water submerged conditions can be simulated.
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CHAPTER 2 RESEARCH APPROACH
2.1 Laboratory Experiment
2.1.1 Materials Two types of coarse aggregates (limestone and granite) with two different grain
size distributions (#7 and #89 specified in ASTM C 33) were considered in this study. Latex polymer, styrene butadiene rubber (SBR) (0.91 specific gravity and 53% water content), was added into the mixtures to improve the bonding strength. Polypropylene monofilament fibers with a length of 19 mm, a tensile strength of 680 MPa, and a specific gravity of 0.9 were also added into the PCPC mixtures to improve their abrasion resistance. 2.1.2 Mix Design
The basic mix proportion for the control mix is cement:coarse aggregate:water = 1:4.5:0.35 by weight. Based on the findings from previous studies by the authors, all the mixtures contained a small amount of natural sand in order to guarantee the strength, and the sand was used to replace 7% coarse aggregate in the mixtures by weight. For the mixtures containing latex and/or fiber, the portion of latex was used to replace 10% cement by weight and the amount of fiber was 0.9 kg/m3 as recommended by the manufacturer. The mix proportions of the PCPC mixtures are presented in Table 2-1.
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Table 2-1 Mix Proportions for PCPC (unit: kg/m3)

Viscosity

Aggregate

Mix Type

Cement

Latex

Coarse Aggregate

Natural Sand

Water

Fiber

HRWR (l)

AEA (l)

Modifying Admixture

(l)

G1 357 -- 1428 100 132 -- 1.29 --

--

G2 351 35 1403 98 116 -- 1.26 --

--

LS

G3 357 -- 1428 100 132 0.9 1.29 --

--

G4 351 35 1403 98 116 0.9 1.26 --

--

#7

G1 353 -- 1414 99 131 -- 1.27 --

--

G2 347 35 1389 97 115 -- 1.25 --

--

GR

G3 353 -- 1414 99 131 0.9 1.27 --

--

G4 347 35 1389 97 115 0.9 1.25 --

--

G1 371 -- 1485 104 137 -- 1.34 --

--

G2 365 37 1459 102 120 -- 1.31 --

--

LS

G3 371 -- 1485 104 137 0.9 1.34 --

--

G4 365 37 1459 102 120 0.9 1.31 --

--

#89

G1 367 -- 1468 103 136 -- 1.32 --

--

G2 361 36 1442 101 119 -- 1.30 --

--

GR

G3 367 -- 1468 103 136 0.9 1.32 --

--

G4 361 36 1442 101 119 0.9 1.30 --

--

GR G5 382 38.2 1420 107 100 - 1.15 --

0.5

G6 388 -- 1442 109 138 - 1.16 --

0.5

#89*

G7 388 38.8 1442 109 101 -- 1.16 --

0.5

LS G8 388 --

1442

109 138 -- 1.16 0.39

0.5

G9 388 38.8 1442 109 101 -- 1.16 0.39 0.5

Note: LS-Limestone, GR-Granite, G1-Control, G2-Latex modified, G3-Fiber added, G4-Latex & Fiber modified, HRWR-High Range Water Reducer, AEA-Air Entraining Admixture.
*-These mixtures are produced for the freeze-thaw test and comparison with field mixtures.

2.1.3 Sample Preparation

Pervious concrete mixtures were mixed using a mechanical mixer, and samples were made by applying standard rodding for compaction. The specimens were cured in a
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standard moisture curing chamber until the days of testing. The laboratory tests and the specimens dimensions for these test are summarized in Table 2-2.

Table 2-2 Laboratory Test Summary

Test

Specification

Compressive strength
Splitting tensile strengh

ASTM C 39 ASTM C 496

Effective air voids ASTM D 7063

Permeability

Florida Method (2006)

Cantabro abrasion ASTM C 131

APA abrasion

N/A

Sweep Abrasion Draindown Freeze-Thaw

N/A
N/A
ASTM C 666 Procedure A

Specimen

Testing machine

Dimensions

(in.)

Cylinder, 4-in.

INSTRON

diameter and 8 in.

high

Cylinder, 6-in.

MTS

diameter and 3 in.

thick

Cylinder, 6-in.

Corelok

diameter and 3 in.

thick

Modified

Cylinder, 6-in.

Karol-Warner diameter and 3 in.

permeameter

thick

Cylinder, 6-in.

LA abrasion machine diameter and 4 in.

thick

Beam 12 in. long by

APA

5 in. wide by 2 in.

high

Sweep machine

Disk, 12-in. diameter and 2 in. thick

N/A

Fresh mixture

Freezing and Thawing Machine

Beam, 16 in. long by 3 in. wide by 4 in. high

2.1.4 Test Methods

2.1.4.1 Air Voids Test
In order to obtain the air voids content, it is necessary to know the bulk volume of the compacted concrete. Since the pervious concrete has highly interconnected air voids, it is not suitable to use the submerged weight measurement to obtain the bulk volume. Geometrical measurement of the specimen dimension will not reflect the surface texture
7

(for different sized aggregates). A vacuum package sealing device, CoreLok, commonly used to measure the specific gravity for asphalt mixtures, was used to obtain the bulk specific gravity for the pervious concrete specimens. The test was conducted by following the ASTM D7063 procedures. The specimen preparation and testing procedures are shown in Figure 2-1.
Figure 2-1 Air Voids Test 2.1.4.2 Permeability Test
Permeability is an important parameter of pervious concrete, since the material is designed to perform as drainage layer in pavement structures. Due to the high porosity and the interconnected air voids path, the Darcy's law for laminar flow is not applicable to pervious concrete. In this study, a permeability measurement device and method developed by Huang et al. (1999) for drainable asphalt mixture (similar to pervious concrete in function) was used. Cylindrical specimens 75 mm thick were selected for this test. Figure 2-2 shows the permeability test setup. Detailed information about the device and the analysis method can be found in Huang et al. (1999).
8

Figure 2-2 Permeability Test Setup and Sample
2.1.4.3 Compressive Strength Test
The compressive strength was tested at 28 days by following the ASTM C39 testing procedures. The compressive strength test was conducted on an INSTRON loading frame on triplicate cylindrical specimens with a 100-mm (4 in.) diameter and a 200-mm (8 in.) height (Figure 2-3).

(a) Before test

(b) After test

Figure 2-3 Compressive Strength Test

9

2.1.4.4 Split Tensile Strength Test

The split tensile test was conducted on triplicate cylindrical specimens of 150-mm

(6-in.) diameter and 63.5-mm (2.5 in.) thickness. The test was performed on an MTS

loading frame in accordance with the procedures ASTM C496/C 496M (Figure 2-4). The

vertical load was continuously recorded, and split tensile strength was computed as

follows:

St

=

2Pult tD

(1)

where:

St = split tensile strength; Pult = peak load; t = thickness of specimen; and

D = Diameter of the specimen, mm

(a) Before test

(b) After test

Figure 2-4 Split Tensile Strength Test

2.1.4.5 Cantabro Test
The Cantabro test was conducted with the Los Angeles (LA) abrasion machine (ASTM C 131) without the steel ball charges (Figure 2-5). The weight loss after the
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Cantabro test (called Cantabro loss) is calculated in percentage using Equation (2):

Cantabro Loss = W1 - W2 100

(2)

W1

where:

Cantabro loss = weight loss, %;

W1 = initial sample weight, g; and

W2 = final sample weight, g.

Figure 2-5 LA Abrasion Machine
2.1.4.6 APA Abrasion Test
The Asphalt Pavement Analyzer (APA) with modified studded wheels was utilized to carry out the loaded wheel abrasion test as shown in Figure 2-6. The APA is the second-generation, multifunctional Loaded Wheel Tester (LWT) used for evaluating the permanent deformation (rutting), fatigue cracking and moisture susceptibility of asphalt concrete. It features controllable wheel load and contact pressure that are representative of actual field conditions.
In this study, triplicate beam specimens for each mix were tested submerged in water. Before testing, all the specimens were dried in an oven for at least 24 hours at 30C. The specimens were put into the APA after cleaning the surfaces by removing loose particles using a steel brush. The tests were set up for 5000 cycles with the frequency of 1 Hz. The load level of 890 N (200 lbf) for each wheel was selected to provide sufficient
11

abrasive and impacting force. During the test, the APA machine was connected to a computer, which controlled the movement of the wheels and automatically performed data acquisition to take the measurements of the wear depth corresponding to the number of cycles. The abraded area by wheels is around 116 cm2. Two parameters, weight loss and wear depth, were used to evaluate the abrasion resistance for the APA test.

(a) Asphalt Pavement Analyzer (APA)

(b) Studded wheel

Figure 2-6 APA Abrasion Test

2.1.4.7 Sweep Abrasion Test
After the weight of the concrete specimens was measured, the specimens were mounted to the sweep test setup for the abrasion test. The testing procedures are as follows: (1). Put the specimen into the aluminum pan and together they are mounted to the testing
device; (2). Use the clamping device to attach the specimen and the pan to the plate tightly; (3). The rubber brush is secured into the brush holder, and the brush head with the weight
is attached to the mixer (Figure 2-7); (4). The brush head is released to make contact with the specimen to ensure that the brush
head can move freely under the vertical load; (5). Start the machine to conduct the sweep test on the concrete specimen; and (6). After the test, the specimen is removed from the clamping device. Any loose
aggregate is removed by hand brushing and weighed.

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Figure 2-7 Sweep Abrasion Test
2.1.4.8 Draindown Test The draindown test is usually used to determine the amount of draindown in
asphalt mixtures, such as open graded friction course (OGFC) and stone matrix asphalt (SMA) mixtures (Brown and Mallick 1994). This test was employed in this study to determine the amount of drain-down for fresh pervious concrete in case that draindown of portland cement paste or mastic will be a problem for construction. Approximately 1200 g freshly mixed pervious concrete mixture was carefully transferred in the wire mesh basket made with standard 6.3-mm (1/4 in.) wire sieve cloth (Figure 2-8). Pre-weighed plates were placed underneath the wire baskets to collect and weigh the drippings at 30-minute intervals for a two-hour period. The percent draindown is reported as the weight of dripping divided by the initial weight of mixture.
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Figure 2-8 Draindown Test

2.1.4.9 Freeze-Thaw Test

The freeze-thaw test was conducted to determine the freeze-thaw resistance of

pervious concrete using Procedure A of ASTM C 666 procedure, in which specimens

were subject to freezing and thawing in the saturated condition (Figure 2-9). Relative

dynamic modulus and mass loss are used to characterize the freeze-thaw durability of

pervious concrete. The durability factor was calculated using Equation (3):

DF = PN

(3)

M

where:

P = relative dynamic modulus of elasticity or relative mass at N cycles in percent,

N = number of cycles at which P reaches the specified minimum value for discontinuing

the test or the specific number of cycles at which the exposure is to be terminated,

whichever is less. The criteria for P were 60% for RDM or 3, 5, or 15% when

calculated for mass, and

M = specified number of cycles at which the exposure is to be terminated, 300 cycles

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Figure 2-9 Freeze-Thaw Test

2.2 Field Project

With the help from the Tennessee Concrete Association, a pervious concrete field project was conducted at the Transit-Mix Concrete Company on April 20, 2010 (Figure 2-10). #8 (specified in ASTM C 33) limestone was used as coarse aggregate in the field mixtures. The mixtures were mixed and placed in three batches, and their mix proportions are shown in Table 2-3. Samples were made on the job site, and cores were taken after three weeks for laboratory testing.

Table 2-3 Perivous Concrete Mix Proportions in Field Project (unit: kg/m3)

Batch No.

Volume (m3)

Aggregate

Mix Type

Cement (type I)

Latex

Coarse Aggregate

Natural Sand

Water

VMA (ml)

Water Reducer
(ml)

Fiber

1 1.7

Latex 360 36 1440 100 110 470 690 --

2

1.7

#8 Limestone

Latex

360

36

1440

100 95 940 690 --

3 2.3

Fiber 350 -- 1490 100 90 470 700 0.9

15

Figure 2-10 Field Project 16

CHAPTER 3 EXPERIMENTAL RESULTS AND ANALYSIS
3.1 Air Voids Results
The air voids test results are shown in Figure 3-1. It can be seen from Figure 3-1 that most of the mixtures had effective air voids within the range of 20% to 30% for the #7 aggregates and 15% to 20% for the #89 aggregates, which could lead to acceptable permeability as shown in the permeability results below (ACI 2008). It is observed that the #7 aggregates produced higher air voids than the #89 aggregates, which was also reflected from the results from the permeability test. This indicates that aggregate gradation has an important effect on the porosity of pervious concrete.
Figure 3-1 shows that the addition of latex resulted in a slight decrease in porosity. The mixes added with fiber showed air voids results similar to those of the control mixes. The mixes made with latex and fiber could still achieve the acceptable porosity and permeability properties.
Figure 3-2 compares the air voids results from laboratory and field mixtures. Field cores seem to exhibit higher air voids than the field prepared samples due to the difference in compaction. With the decrease in water content, the field mixtures exhibited an increase in air voids (Batch 3 > Batch 2 > Batch 1). Figure 3-2 shows that properly designed mixtures could obtain the required air voids for pervious concrete.
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(a) #7 Aggregates
(b) #89 Aggregates Figure 3-1 Effective Air Void Results
18

Effective Air Voids (%)

Field Prepared Samples 30
Field Cores
25

20

15

10

5

0

F1

F2

F3

Mixture Type

(a) Field Mixtures

Effective Air Voids (%)

30

Lab Prepared Samples

25

20

15

10

5

0

G5

G6

G7

Mixture Type

(b) Laboratory Mixtures Figure 3-2 Comparison of Air Voids of Laboratory and Field Mixtures

3.2 Permeability Results
Table 3-1 presents the results from the permeability test. Based on the results, most of the specimens obtained from the top of the cylinder had much less permeability than those from the middle. It is evident that the mixtures made with the #7 aggregates had larger permeability than the #89 aggregates. The mixtures made with granite also had
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much higher permeability than the mixtures made with limestone. It can also be seen that the effect of latex and fiber on permeability was similar to
that on air voids content. Although the addition of latex could lead to a reduction in permeability, the permeability results were reasonably acceptable compared to the general drainage requirements for pervious concrete pavements.

Table 3-1 Permeability Results (mm/s)

Aggregate
# 7 # 89

Type
Limestone Granite
Limestone Granite

Permeability (mm/s)
Control Latex modified Fiber added top interior top interior top interior 1.53 4.63 0.37 1.36 1.27 4.15 3.86 5.49 1.72 2.71 2.88 3.77 0.41 1.24 0.38 0.53 0.16 1.07 2.03 3.52 0.62 2.18 1.53 3.66

Latex & Fiber top interior 1.08 1.50 2.96 3.74 0.21 0.79 0.30 2.19

The comparison of permeability results from field and laboratory results is presented in Figure 3-3. The field mixture Batch 3 exhibited the highest permeability, followed by Batch 2. Batch 1 had the lowest permeability. This was consistent with the air voids results. The permeability results from the laboratory mixtures were also consistent with the air voids results and could meet the water permeability requirement for pervious concrete.

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Field Prepared Samples 4
Field Cores
3

Permeability (mm/s)

2

1

0

F1

F2

F3

Mixture Type

(a) Field Mixtures
4 Lab Prepared Samples
3

Permeability (mm/s)

2

1

0

G5

G6

G7

Mixture Type

(b) Laboratory Mixtures

Figure 3-3 Comparison of Air Voids of Laboratory and Field Mixtures

3.3 Compressive Strength Results
The results from the compressive strength test are presented in Figure 3-4. Based on the results, the smaller the coarse aggregate size, the higher the compressive strength. It is evident that the addition of latex can increased the compressive strength of pervious concrete mixtures, because latex could increase the contact area between neighboring aggregate particles. More importantly, the latex and the cement hydration products could commingle and create two interpenetrating matrices which work together, resulting in
21

improved strength. It is also observed from Figure 3-4 that fibers had no remarkable contribution to the compressive strength.
(a) #7 Aggregates
(b) #89 Aggregates Figure 3-4 28-Day Compressive Strength Results Figure 3-5 compares the compressive strength at 28 days from the field and laboratory mixtures. With the increase in air voids, the field mixtures showed a decrease in compressive strength (Batch 3 < Batch 2 < Batch 1). The compressive strength from the laboratory mixtures ranged from 20 MPa to 30 MPa, which was comparable to the results in Figure 3-4.
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Compressive Strength (MPa)

60

50

40

30

20

10

0

F1

F2

F3

G5

G6

G7

G8

G9

Mixture Type

Figure 3-5 Comparison of Compressive Strength of Laboratory and Field Mixtures

3.4 Split Tensile Strength Results
The results from the split tensile strength test are presented in Figure 3-6. Similar to the compressive strength results, concrete mixtures containing smaller size aggregates had higher split tensile strength. The effect of latex was still significant in improving the split tensile strength of pervious concrete. This could be attributed to the latex network formed during the commingling and inter-penetration of the latex and cement hydration products. Unlike the brittle cement mortar, the latex network is relatively strong in tension, which will contribute significantly to the split tensile strength of pervious concrete.
The strength results of the mixtures with fibers were similar to those of the control mixtures, which indicates that fiber did not have a significant effect on the split tensile strength of pervious concrete. This also verified the findings from the previous study that use of fiber did not significantly increase the split tensile strength of pervious concrete.

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(a) #7 Aggregates
(b) #89 Aggregates Figure 3-6 28-Day Split Tensile Strength Results The results for the field and laboratory pervious concrete mixtures are compared in Figure 3-7. Field mixture Batch 1 had the highest split tensile strength, followed by Batch 2, which was consistent with the air voids results. The results from the laboratory results were similar.
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Split Tensile Strength (MPa)

4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0
F1

Field Prepared Samples Field Cores

F2

F3

Mixture Type

(a) Field Mixtures
2.5
Lab Prepared Samples
2

1.5

1

0.5

0

G5

G6

G7

Mixture Type

(b) Laboratory Mixtures

Figure 3-7 Comparison of Split Tensile Results

Split Tensile Strength (MPa)

3.5 Cantabro Test Results
In the Cantabro test, the final revolution number was 300 cycles and the specimen weight was measured every 50 cycles. Figure 3-8 shows that change of specimens with
25

the revolution cycles. The weight loss results are presented in Table 3-2.

(a) Before test

(b) 50 cycles

(c) 100 cycles

(d) 150 cycles

(e) 200cycles

(f) 250 cycles

(g) 300cycles

Figure 3-8 Specimens in Cantabro Test

From Table 3-2, the weight loss results varied with different pervious concrete mixtures. The weight loss for the mixtures with high abrasion resistance increased fast at the beginning of the test. However, the increase rate of weight loss gradually decreased with the increase in the revolution cycle. For the mixtures with weak abrasion resistance, the weight loss increased even faster after 200 cycles. The total weight losses for the Cantabro abrasion test after 300 cycles ranged from 10% to 35%, as shown in Figure 3-9.
It is observed that the pervious concrete mixtures made with latex had higher abrasion resistance than those without latex. Fiber slightly improved the abrasion resistance of concrete mixtures with #7 aggregate. However, fiber did not have a significant effect on the abrasion resistance of mixtures made with #89 aggregate. Compared to the mixtures made with latex or fiber, the mixtures with both latex and fiber added did not show significant improvement in abrasion resistance.

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Table 3-2 Weight Loss Results from Cantabro Test

Weight Loss (%)

Aggregate

Mix Type

Revolution Cycles

50 100 150 200 250 300

Control

6.7 17.1 25.8 33.5 70.3 83.3

Latex modified 4.8 9.2 13.6 18.4 22.4 25.3 LS
Fiber added 5.9 10.4 17.3 22.1 30.0 35.1

# 7

Latex & Fiber 7.0 13.1 18.3 22.0 26.6 32.2

Control

4.7 8.8 17.8 24.6 34.0 43.0

GR Latex modified 5.7 10.7 15.2 18.7 22.1 25.1 Fiber added 6.0 10.4 14.8 19.8 27.3 32.4

Latex & Fiber 5.5 8.9 12.2 15.7 20.2 23.4

Control

5.4 9.7 13.3 16.8 20.0 23.2

LS Latex modified 3.1 5.0 Fiber added 3.6 6.8

6.7 8.8 11.1 13.2 9.6 11.9 14.6 16.7

Latex & Fiber 3.7 5.8 7.4 9.5 11.2 13.0

# 89

Control

5.4 10.6 14.5 18.6 22.1 25.7

Latex modified 3.9 6.4 8.7 11.0 12.7 14.9 GR
Fiber added 5.8 10.6 15.3 19.3 23.1 27.8

Latex & Fiber 3.9 6.9 9.3 12.4 15.4 17.9

* LS-Limestone; GR-Granite

Weight loss, %

100

90

#7 limestone #7 granite

80

#89 limestone #89 granite

70

60

50

40

30

20

10

0

Control Latex modified Fiber added Latex & Fiber

Type Figure 3-9 Weight Loss Results after 300 Cycles

The comparison of the Cantabro test results from laboratory and field mixtures is
presented in Figure 3-10. Except the field mixture Batch 3, all the mixtures experienced a 27

weight loss less than 20% after 300 revolution cycles.

Weight Loss (%)

30

Field or lab prepared samples

25

Field cores

20

15

10

5

0

F1

F2

F3

G5

Mixture Type

Figure 3-10 Comparison of Weight Loss from Cantabro Test

3.6 APA Abrasion Results
Two parameters, weight loss and depth of wear, were used to evaluate the abrasion resistance in the APA abrasion test. The results are shown in Figure 3-11. The weight loss fell within the range of 1.6%-3.5% (60-150 g) for #7 aggregate mixtures and 0.8%-1.5% (30-60 g) for #89 aggregate mixtures. The depth of wear ranged from 3.5 mm to 5.0 mm for #7 aggregate mixtures and from 1.5 mm to 3.5 mm for #89 aggregate mixtures. Based on these results, PCPC with finer aggregates had higher abrasion and raveling resistance than PCPC with coarser aggregate.
Considering both weight loss and depth of wear, the most desirable pervious concrete mixtures were the latex-modified ones with the #89 aggregate. It is also concluded that latex was better than fiber in improving the abrasion resistance of pervious concrete.

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Weight loss, %

5.0

#7 limestone

#7 granite

4.0

#89 limestone #89 granite

3.0

2.0

1.0

0.0 Control Latex modified Fiber added Latex & Fiber Type

(a) Weight loss

5.0

#7 limestone

#7 granite

4.0

#89 limestone #89 granite

3.0

2.0

1.0

0.0

Control

Latex modified Fiber added Latex & Fiber

Type

(b) Depth of wear Figure 3-11 APA Abrasion Test Results

Depth of wear, mm

3.7 Sweep Abrasion Test Results
After several trials, it turned out that the solid rubber hoses were not strong or hard enough to abrade the surface of pervious concrete. No apparent aggregate losses were observed on the specimens, and the weight loss was almost zero. A heavier vertical load and a steel brush are recommended for future study.

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3.8 Draindown Test Results
The draindown test was conducted on the field mixtures at the jobsite. It was found that only very few drippings were observed for the mixtures and that the percent draindown was almost zero. This can be attributed to the use of viscosity modifying admixture in field mixtures. With the addition of this mixture in pervious concrete mixture, draindown should not be a problem.
3.9 Freeze-thaw Test Results
The change of mass and dynamic modulus of elasticity of the specimens in the freeze-thaw test is shown in Figure 3-12. It can be seen that with the increase in the freeze-thaw cycles, both the mass and the dynamic modulus of elasticity of the specimens decreased. Compared to the mass loss, the dynamic modulus of elasticity started to decrease later. However, once started, the dynamic modulus deteriorated much faster than the mass loss. Figure 3-12, the field mixtures Batch 1 and Batch 2 and the laboratory mixtures with air entraining admixture (AEA) (G8 and G9) seemed to perform better than the other mixtures.
Table 3-3 presents the durability factors obtained from the freeze-thaw test. The durability factors were calculated based on the results at 180 cycles. The criteria for test cutoff were taken as 60% for RDM or 3, 5, or 15% for mass loss following the suggestions by Kevern et al. (2010). The results clearly show that two field mixtures (Batch 1 and Batch 2) and two laboratory mixtures (G8 and G9) performed much better than the other mixtures. Batch 1 performed well because of its low air voids and permeability. Mixtures G8 and G9 performed well because they contained air entraining admixture. This indicated that even for pervious concrete, AEA could help to improve the freeze-thaw durability.
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100%

Mass Remaining

90%
80%
70%
60% 0

F1 F2 F3 G5 G6 G7 G8 G9
30 60 90 120 150 180 210 240 270 300 Freeze-Thaw Cycles
(a) Mass Loss

100%

Relative Dynamic Modulus

80%

F1

60%

F2

F3

G5 40%
G6

G7

20%

G8

G9

0% 0

30 60 90 120 150 180 210 240 270 300 Freeze-Thaw Cycles

(b) Relative Dynamic Modulus Figure 3-12 Change of Mass and Relative Dynamic Modulus with Freeze-Thaw
Cycles

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Table 3-3 Durability Factors from Freeze-Thaw Test

Mixture

Mix

DF (RDM)

Designation 60%

Field Mixtures

Batch 1 Batch 2 Batch 3

F1 (with latex) F2 (with latex)
F3

44.7% 47.7% 24.5%

Granite G5 (with latex) 24.9%

Limestone G6 (control) 24.2%

Laboratory Limestone G7 (with latex)

Mixtures Limestone

G8 (with AEA)

25.7% 76.6%

Limestone

G9 (with AEA and latex)

38.6%

DF (% Mass Remaining) 85% 95% 97% 97.7% 97.7% 97.7% 96.2% 96.2% 91.6% 51.0% 47.9% 42.5% 51.0% 45.9% 43.8% 54.5% 55.6% 47.7% 59.6% 52.9% 50.0%
97.8% 97.8% 97.8%
77.0% 63.0% 59.0%

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CHAPTER 4 CONCLUSIONS AND RECOMMENDATIONS
z Latex could significantly improve the strength and abrasion resistance and slightly decrease the air voids and permeability of PCPC. Fiber had no significant effect on the mechanical properties and abrasion resistance of PCPC.
z PCPC made with large size aggregate had weaker mechanical properties and abrasion resistance than the mixes made with small size aggregate, mainly due to the reduced contact area between adjacent aggregate particles.
z Both the Cantabro and APA abrasion tests were effective for assessing the abrasion resistance of pervious concrete. and they are also effective methods to assess bonding properties between aggregate particles. The two parameters, weight loss and wear depth, could both be used as an indicator of abrasion resistance in the APA test.
z The Cantabro test experienced much higher weight loss than the APA abrasion test, which was largely due to the over aggressive impact force and the sharp edges of the specimens. The materials used in this study could be differentiated after 100 revolutions. The final revolution number used in this study (300 cycles) may be reduced in the future.
z The relatively optimum ranges of the properties of PCPC mixtures are 15~20% effective air voids, 1.0-2.0 mm/s permeability and 20-25 MPa compressive strength. Properly-designed mixtures could meet these requirements.
z Even for pervious concrete, inclusion of air-entraining admixture still could help to improve the freeze-thaw durability.
z A small-sized field project validated the findings from the laboratory mixtures. z The sweep abrasion test might not be useful for the evaluation of abrasion resistance
of pervious concrete. z With the use of viscosity modifying admixture, draindown was not a problem for
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pervious concrete mixtures. z These findings are based on the results from a laboratory study and a small field
project. A relatively large field project is recommended to verify the abrasion and durability performance of pervious concrete in future study.
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