AN EXPERIMENTAL INVESTIGATION ON HIGH

STRENGTH FIBER REINFORCED

PERMEABLRECONCTRETE

A PROJECT REPORT

Submitted by

ARAVINTH.N (922516103006)
BRITHIVIRAJ.S (922516103008)
CHANDRA PRAKASH (922516103009)

in partial fulfillment for the award of the degree

of

BACHELOR OF ENGINEERING
IN

CIVIL ENGINEERING

V.S.B COLLEGE OF ENGINEERING

KARUR

ANNA UNIVERSITY: CHENNAI-600 025

AUGUST- 2020
 ANNA UNIVERSITY:CHENNAI -600 025

BONAFIDE CERTIFICATE

Certified that this project report “INCREASING STRENGTH

OF PERMEABLE CONCRETE BY USING STEEL FIBER
REINFORCING” is the bonafide work of “ARAVINTHG.N
(922516103006) , BRITHIVIRAJ(922516103008), CHANDRA
PREKASH (922516103009), who carried out the project work under
my supervision.

SIGNATURE SIGNATURE
Mr.R.GOWRISHANKAR,M.E., Mr.C.MOHANASELVAN,M.E.,
HEAD OF THE DEPARTMENT SUPERVISOR,
Department of Civil Engineering, Assistant Professor,
V.S.B.College of Engineering Department of Civil Engineering,
and Technology, V.S.B.College of Engineering
Karur-639 003. and Technology,
Karur- 639 003.

Submitted to the Project and Viva Examination held on ………..

INTERNAL EXAMINER EXTERNAL EXAMINER

 ACKNOWLEDGEMENT

At the outset I would like to express my praise and gratitude of God

Almighty for his supreme guidance, strength and ways for accomplishing this project
work successfully

We convey our thanks to our honorable Chairman Sir

SHRI.V.S.BALSAMY, B.Sc., B.L, L.L.B., and trustees for providing all
the
facilities to complete the project successfully.

We also express our thanks to our honorable Principal Sir

Dr.V.NIRMALKANNAN, M.E., Ph.D., for following us to use all

facilities that are available in our college, to complete the project.

We would like to express our thanks to our Head of Department

Mr.R.GOWRISHANKAR, M.E., for helping us to finish the project.

We take immense pleasure to express our sincere thanks to our project

guide Mr.C.MOHANASELVAN,M.E., for giving his valuable support and guidance
at all the time to complete this project a successful one on time.

We also extent our gratitude to our project Coordinators,

Mr.K.RAJKUMAR, M.E., and Mr.N.VIGNESHWARAN, M.E, for
their valuable suggestions.

Last but not least, we thank our PARENTS and beloved

FRIENDS for their moral support.
 ABSTRACT

One of the main objectives of this research was to develop preliminary

specifications for high quality pervious concrete suitable for use in Tamil Nadu State
Highway Administration (SHA) projects. The study utilized aggregates that are used
and the durability studies were conducted assuming Indian weather
conditions. Investigations were conducted to enhance the structural and durability
characteristics of pervious concrete through the use of different admixtures. The
admixtures included cellulose fibers, a delayed set modifier and a viscosity modifier.
Pervious concrete specimens were tested for density, void content, compressive strength,
split tensile strength, permeability, durability, and abrasion resistance.

iv
 TABLE OF CONTENTS
CHAPTER TITLE PAGE
NO. NO.
ABSTRACT iv
TABLE OF CONTENTS v
LIST OF TABLES vii
LIST OF FIGURES viii
LIST OF NOTATIONS ix
1. INTRODUCTION 1
1.1 Back Ground 1
1.2 Problem Statement 2
1.3 Scope of Work 3
1.4 Outline of Report 3
2. LITERATURE REVIEW 4
3. METHODOLOGY 8
3.1 General 8
3.2 Material 8
4. MATERIAL PROPERTIES 14
4.1 General 14
4.2 Types of Pervious Pavements 15
4.3 Detention and Retention Designs 17
4.4 Passive or Active Mitigation System 17
4.5 Material Properties 18
4.6 Permeability 25
4.7 Construction and Maintenance 29
5. MIX DESIGN 34
5.1 Mix Design 34
6. EXPERIMENTAL TEST AND RESULTS 38
v
 Density and Void Ratio 38

Compressive Strength Test 41

Split Cylinder Test 47

Permeability Test 50
6. RESULT AND DISCUSSIONS 54
Delayed Set Modifier Results 54

Viscosity Modifier Results 55

Fibre Results 56
7. CONCLUSION 57
REFERENCES 58

vi
 LIST OF TABLES

TABLE TITLE PAGE

NO. NO.
3.1 Aggregate Properties 8
5.1 Concrete Mixture Properties 35
5.2 Material Quantities 36
6.1 Density and Theoritical Density of the 40
Pervious Concrete
6.2 Calculated Void Content 41
6.3 7 Day Compressive Strength 43
6.4 14 Day Compressive Strength Result 44
6.5 28 Day Compressive Strength Result 45
6.6 120 Day Compressive Strength Result 46
6.7 Tensile Strength Result 49
6.8 Permeability Results 53

vii
 LIST OF FIGURES

FIGURE TITLE PAGE

NO. NO.
3.1 Aggregate Properties 7
3.2 Tensile Strength Test 8
3.3 Compressive Strength Test 9
3.4 Density And Void Test 10
3..5 Permiability Test 11
4.1 Setion Of a Typical Pervious Concrete 13
4.2 Type Of Pervious Pavements a,b,c 14
4.3 Relationship Between Fine Aggregate And 18
Porosity
4.4 Pervious Concrete With a,b,c 19
4.5 Relationship Between Waterm to Cement And 20
Compressivr Strength
4.6 Ponding of Water to Occur on Sloped 24
Pavement
4.7 Sloped Pervious Concrete Pavement With Dug 25
Trenches Filled with Stone
4.8 Structural Plane and Elevation of a Sloped 25
Pervious concrete Pavement
4.9 Mechanical Vibrating screed 27

4.10 Use of a Steel Roller 27

5.1 Concrete Mixture Properties 31
5.2 Material Quantities 32
6.1 Apparatus Used for Density and Void Content 35
6.2 Pervious Concrete Specimen in Compression 38
Testing Machine
6.3 Correlation between Void Content and 43
Compressive Strength
6.4 Split Tensile Strength Test with Bearing Strips 44
Prior to Loading

viii
`

LIST OF NOTATIONS
The following symbols carrying the meaning noted against them. Which are used in this project work.

psi : Pound per square inches

mm : Millimeter

OPC : Ordinary Portland Cement

PPC : Portland Pozzolanic Cement

UTM : Universal Testing Machine

CTM : Compression Testing Machine

lbs : Pound

MPa : Mega pascal

pcf : Pounds per Cubic Feet

Cc : Curvature Coefficient

Uc : Uniformity Coefficient

Kg : Kilo gram

IS : Indian Standard

in : Inch

hr : Hour
 CHAPTER- I

INTRODUCTION

1.1 Background
Portland cement pervious concrete (PCPC) is gaining a lot of attention. Various
environmental benefits such as controlling storm water runoff, restoring groundwater
supplies, and reducing water and soil pollution have become focal points in many
jurisdictions across the United States (Kajio et al 1998). Portland cement pervious
concrete is a discontinuous mixture of coarse aggregate, hydraulic cement and other
cementations materials, admixtures and water. By creating a permeable surface, storm
water is given access to filter through the pavement and underlying soil, provided that
the underlying soil is suitable for drainage. This allows for potential filtration of
pollutants. To achieve this permeability, PCPC is typically designed with high void
content (15-25%). The U.S. EPA has published a Porous Pavement fact sheet (US EPA
1999) that lists the advantages of pervious pavements. These advantages are:
• Water treatment by pollutant removal;

• Less need for curbing and storm sewers;

• Improved road safety because of better skid resistance; and

• Recharge to local aquifers.

While it is seen as a new and emerging application, pervious concrete does have
its disadvantages. Poor performances in cold regions, arid regions, regions with high
wind erosion rates, and areas of sole-source aquifers have shown the downside of using
pervious concrete (Pratt 1997). In addition, the use of porous concrete is highly
constrained, requiring deep permeable soils, restricted traffic, and adjacent land uses.
Although PCPC has seen an increase in application in recent years, there is still limited
experience with the material. According to the EPA, approximately 75 percent of
pervious concrete pavements have failed. This has been attributed to poor design,
inadequate construction techniques, low permeability soil, heavy vehicular traffic, and
poor maintenance (US EPA 1999). Failure has been determined by the EPA as a
pervious pavement that can no longer function as a stormwater retention material due to
clogging and/or structural failure. Prior to wide use of pervious concrete in Tamil Nadu,
it is important to study the effect of Tamil Nadu weather conditions with regional
materials used in standard State Highway Administration (SHA) projects.

1.2 Problem Statement

The porosity of pervious pavements is provided by omitting all or most of the fine
aggregates which impart the necessary percolation characteristics to the concrete. In 2001
the American Concrete Institute (ACI) formed committee 522, “Pervious Concrete”, to
develop and maintain standards for the design, construction, maintenance, and
rehabilitation of pervious concrete. This recent interest in porous surfaces as a
substitution for impervious surfaces can be attributed to desirable benefits such as
stormwater retention, which includes stormwater treatment. Because of the high void
content PCPC generally has low strength (800-3000 psi) which limits applications in cold
weather regions and is responsible for various distresses and pavement failures. The need
to develop a high performing pervious concrete specification for Tamil Nadu conditions
was the basis of this report. Several admixtures were tested along with regional materials
often used in SHA projects. Structural and durability characteristics were measured
against a control mix.
Investigation of pervious concrete performance under cold weather conditions has
been studied. Iowa and Minnesota have each funded various projects on pervious
concrete in cold weather regions. However, these states do not have the cyclic freezing
and thawing that occurs in Tamil Nadu.
Currently, Tamil Nadu has not fully adopted a pervious concrete specification but
has been gathering various researches on the subject and has developed a draft
specification based on the ACI 522 Specification. While numerous states have created
such a document, the unique weather conditions in Tamil Nadu in combination with
Tamil Nadu materials have not been evaluated and tested. Several admixtures in
conjunction with typical aggregates found in Tamil Nadu state projects were included in
the design mixtures for this project. Structural and durability tests are needed before a
preliminary specification can be developed for pervious concrete based on materials
indigenous to Tamil nadu and suitable for Tamil Nadu climatic conditions.

1.3 Scope of Work

The present study was conducted to investigate pervious concrete made from
aggregates used in Tamil Nadu State projects under Tamil Nadu weather conditions. In
this study, several admixtures were used and the pervious concrete specimens were
tested for density and void content, compressive strength, split tensile strength,
permeability, freeze-thaw capacity, and abrasion resistance. Testing was performed at
the University of Tamil Nadu College Park campus and Eastern Testing and Inspection
Laboratory (ETI) located in Frederick, Tamil Nadu.

1.4 Outline of Report

This report is divided into six chapters, including this introduction. Chapter 1
outlines the scope of work. Chapter 2 provides the literature review from both national
and international sources. Description and discussion of the different mix designs are
included in Chapter 3. Chapter 4 addresses the procedures for each of the six tests.
 Chapter-2
LITRATURE REVIEW
Bean, E. Z., Hunt, W. F.,
Bidelspach, D. A., “Field Survey of Permeable Pavement Surface Infiltration Rates,”
Journal of Irrigation and Drainage Engineering, Vol. 133, No. 3, June 2007.

ASTM Standard C 192, 2006,

“Standard Practice for Making and Curing Test Specimens in the Laboratory,” ASTM
International, West Conshohocken, PA.ASTM Standard C 260, 2007, “Specification for
Air-Entraining Admixtures for Concrete”, ASTM International, West Conshohocken,
PA.ASTM Standard C 494, 2007, “Specification for Chemical Admixtures for
Concrete”, ASTM International, West Conshohocken, PA.

ASTM Standard C 595, 2007,

“Specification for Blended Hydraulic Cements”, ASTM International, West
Conshohocken, PA.ASTM Standard C 618 “Specification for Coal Fly Ash and Raw
or Calcined Natural Pozzolan for Use in Concrete”, ASTM International, West
Conshohocken, PA.ASTM Standard C 666, 2003, “Standard Test Method for
Resistance of Concrete to Rapid Freezing and Thawing,” ASTM International, West
Conshohocken, PA.

ASTM Standard C 672, 2003,

“Standard Test Method for Scaling Resistance of Concrete Surfaces Exposed to Deicing
Chemicals,” ASTM International, West Conshohocken, PA.ASTM Standard C 989,
2007, “Specification for Ground Granulated Blast-Furnace Slag for Use in Concrete and
Mortars”, ASTM International, West Conshohocken, PA.

ASTM Standard C 1077, 2007,

“Practice for Laboratories Testing Concrete and Concrete Aggregate for Use in
Construction and Criteria for Laboratory Evaluation”, ASTM International, West
Conshohocken, PA.ASTM Standard C 1116, 2007, “Specification for Fiber-Reinforced
Concrete and Shotcrete”, ASTM International, West Conshohocken, PA.ASTM Standard
C 1157, 2007, “Performance Specification for Hydraulic Cement”, ASTM International,
West Conshohocken, PA.ASTM Standard C 1688, 2010, “Test Method for Density and
Void Content of Freshly Mixed Pervious Concrete”, ASTM International, West
Conshohocken, PA.

ASTM Standard C 1701, 2010,

“Test Method for Infiltration Rate of In Place Pervious Concrete”, ASTM
International, West Conshohocken, PA.
ASTM Standard D 7063, 2005,
“Standard Test Method for Effective Porosity and Effective Air Voids of
Compacted Bituminous Paving Mixture Samples,” ASTM International, West
Conshohocken, PA.

Florida Concrete and Products Association,

“Construction of Portland Cement Pervious Pavement, Florida Concrete and Products
Association”, Orlando, Florida, 2004.GCPA, “Recommended Specifications for
Portland Cement Pervious Pavements,” Georgia Concrete and Products Association,
Tucker, Georgia, August 1997.

Haselbach, L.,
Freeman, R.M., ¨Vertical Porosity Distribution in Pervious Concrete Pavement,¨
ACI Materials Journal, Volume 103, No. 6, Nov-Dec 2006, pp. 452-458.

Kajio, S.,
Tanaka, S., Tomita, R., Noda, E., Hashimoto, S., “Properties of Porous Concrete
with High Strength”, Proceedings 8th International Symposium on Concrete Roads,
Lisbon, 1998, pp 171-177.

Kevern, J.T.,
Schaefer, V.R., Wang, K., and Suleiman, M.T., “Pervious Concrete Mixture
Proportions for Improved Freeze-Thaw Durability,” Journal of ASTM International, Vol.
5, No. 2, 2008.

Kwiatkowski, M., Welker,

A.L., Traver, R., Vanacore, M., Ladd, T., “Evaluation of an Infiltration Best
Management Practice Utilizing Pervious Concrete,” Journal of the American Water
Resources Association, Vol. 43, No. 5, 2007, pp. 1208-1222.Mata, L. A., "Design
Guidelines of Pervious Concrete Pavement Systems Subjected to Sedimentation," ACI
Materials Journal 2008.Mathis, D. E. "Permeable bases - An update,” PCA, No. 8.,
Nov., 1990, pp. 3-4.

Meininger,
R.C., “No-Fines Pervious Concrete for Paving,” Concrete International, Vol. 10, Issue
8, Aug 1998 pp. 20-27.Nelson, P. M., Philips, S. M., "Quieter Road Surfaces," TRL
Annual Review, Transportation Research Laboratories, UK, 1994, pp. 13.

NRMCA,
"What, Why, and How? Pervious Concrete," Concrete in Practice Series. CIP 38,
2004.Paine, J., “Portland Cement Pervious Pavement Construction,” Concrete
Construction, September 1992, pages 655 to 659.

Park, S., Tia, M.,

“An Experimental Study on the Water-purification Properties of Porous
Concrete,” Cement and Concrete Research, Vol. 34, 2004, pp.177-184.Pratt,
C.J., “Permeable Pavements: Design and Maintenance. Developments in Storm
Drainage – A Symp. of Infiltration and Storage of Storm Water in New
Developments,” 1990, pp. 136-151.

Ramakrishnan, V.,
“Latex-Modified Concrete and Mortars,” NCHRP Synthesis 179, Transportation
Research Board, National Research Council, Washington, D.C.1992.Rizvi, R.,
Tighe, S.L., Norris, J., Henderson, V., “Incorporating Recycled Concrete Aggregate
in Pervious Concrete Pavements”, Proceeding from the National Transportation
Research Board, 2010.
 CHAPTER-3
METHODOLOGY

3.1 GENERAL
This chapter discusses the pervious concrete mix design, types of materials, and
the procedures used for sample preparation. The research tested three different
admixtures: viscosity modifier, delayed set modifier, and cellulose fiber.

3.2 Materials
To simulate mixtures for use in Tamil Nadu State Highway Administration
(SHA) projects, materials often used for SHA projects were specified. Vulcan materials
supplied the coarse and fine aggregates. The aggregates originated from their quarry in
Hanover.
3.1 outlines the aggregate properties.
Table 3.1: Aggregate Properties

Material Input

Aggregate Properties
Coarse Aggregate
Name of Supplier Vulcan Materials
Location Hanover, PA
Round or Angular Angular
Specific Gravity 2.71
Aggregate Absorption 0.80%
Aggregate
Moisture 1.00%
Fine Aggregate
Specific Gravity 2.62
Aggregate Absorption 1.00%
Aggregate
Moisture 1.00%
 A maximum of 1/2 in. diameter aggregate was used in each mix design. Fine
aggregates were used to help achieve higher design strengths. Portland Type I cement
was used in each mix. One control mix and three mix designs with the following
admixture were batched: viscosity modifier, delayed set modifier, and cellulose fibers.
The following matrices shown in Figures 3.1-3.6 were developed for the different batches
and different tests to be performed:

Pervious Concrete

Compressive Test (C)

Delayed Set Modifier

Control Mix (CM) Cellulose Fibers (CF) Viscosity Modifier (VM)
(DM)

Day: Day: Day: Day: Day: Day: Day: Day:

7a 14a 7a 14a 7a 14a 7a 14a
7b 14b 7b 14b 7b 14b 7b 14b
7c 14c 7c 14c 7c 14c 7c 14c

Day: Day: Day: Day: Day: Day: Day: Day:

28a 120a 28a 120a 28a 120a 28a 120a
28b 120b 28b 120b 28b 120b 28b 120b
28c 120c 28c 120c 28c 120c 28c 120c

Figure 3.1: Compressive Strength Test

 Pervious Concrete

Tensile Test (T)

Control Mix (CM) Delayed Set Modifier (DM) Cellulose Fibers (CF) Viscosity Modifier (VM)

Day: Day: Day: Day:

28a 28a 28a 28a
28b 28b 28b 28b
28c 28c 28c 28c

Figure 3.2: Tensile Strength Test

 Pervious
Concrete

Density and
Void Test (D)

Control Mix Delayed Set Cellulose Viscosity

(CM) Modifier (DM) Fibers (CF) Modifier (VM)

Day: Day: Day: Day:

Fresh Mix Fresh Mix Fresh Mix Fresh Mix

Figure 3.3: Density and Void Test

 Pervious Concrete

Permeability Test (P)

Delayed Set Modifier Viscosity Modifier

Control Mix (CM) Cellulose Fibers (CF)
(DM) (VM)

Day: Day: Day: Day:

28a 28a 28a 28a
28b 28b 28b 28b

Figure 3.5: Permeability Test

 CHAPTER- 4

MATERIAL PROPERTIES
4.1 General
Sustainable construction designs have become extremely popular within the last
few years. Reducing the strain on our environment is essential to the overall health and
wellbeing of our society. While a variety of new designs and technologies have
transpired from this green movement, one of the more profound impacts has been in the
area of stormwater management (SWM). Named one of the best management practices
for SWM quality, pervious concrete has the ability to capture the runoff of rainwater and
remove trace pollutants (NRMCA 2004). While pervious concrete has been around for
many years, it has seen a significant increase in interest in recent years with the adoption
of the federal clean water legislation. One of its first uses was in southern Georgia where
the preservation of the natural ecosystem played an important role in selecting pervious
concrete (Ferguson 2005). Since then, other states such as Florida, New Mexico, Utah,
California, Oklahoma, Illinois, and Wisconsin have implemented pervious concrete
designs (Mathis 1990).
Pervious concrete can be defined as an open graded or “no-fines” concrete that
allows rain water to percolate through to the underlying sub-base (ACI Committee 522
2006). The principal ingredients are quite similar to conventional concrete: aggregate,
Portland cement, admixtures, fine aggregate (optional), and water. The main difference
is the percentage of void space within pervious concrete. Typical ranges of void space
are between 15-25 percent or roughly .08 in to .32 in (2 mm to 8 mm) (NRMCA 2004).
To create a pervious concrete pavement, the pervious concrete (ranging from 4 to 8
inches in thickness) is placed on top of an aggregate base. The thickness of this
aggregate base is dependent on a number of influencing factors. A filter fabric can be
placed to separate the underlying soil from the pervious concrete (see Figure 2.1). This
allows the impediment of the soil from percolating or penetrating up and clogging the
pores of the concrete (Tennis et al 2004). The use of sub-base material is dependent on
soil conditions as well as the intended application.

Figure 4.1: Section of a Typical Pervious Concrete Pavement

4.2 Types of Pervious Pavements

There are several types of pervious pavements that are used in practice. The three
common types as shown in Figure 2.2 are pervious concrete, pervious interlocking
concrete pavers, and concrete grid pavers (Collins et al 2008 and Bean et al 2007).
 a.

b.

c.

Figure 4.2: Types of Pervious Pavements a. Pervious Concrete, b. Pervious

Interlocking Concrete Pavers, c. Concrete Grid Pavers
 4.3 Detention and Retention Designs
While the key element in designing any pervious concrete pavement is the
limitation of stormwater runoff, pervious concrete pavements may be classified as either
detention design or a retention design. To be classified as a detention pervious pavement,
the design must detain the stormwater until it is discharged into the drainage network. To
be classified as a retention pervious pavement, the design must not only hold the
stormwater but also retain and treat until infiltration can occur into the underlying soil.
The retention system is heavily dependent on the underling soil properties. A subsurface
with low permeability (i.e. clay) may not be able to effectively drain the water prior to the
next storm event. If this should occur, saturation and percolation up through the pervious
concrete could be imminent (Tyner et al 2009).
For the retention system, the ability to treat the stormwater is extremely
beneficial. Two types of treatment can occur: mechanical and biological (Schaefer et al
2006). For a mechanical treatment, the particles are trapped on the concrete surface. For
a biological treatment, the particles are degraded on the concrete surface or at the sub-
base level. A mechanical treatment was tested by Pratt et al (1990) to determine the
effect pervious concrete had with entrapping motor oil. By placing a small amount of
motor oil on a one square foot specimen and simulating three rainfalls, he was able to
determine that the pervious concrete was able to retain 99.6% of the motor oil.
Biological treatment processes were also evaluated (Pratt et al 1990). Microorganisms
were applied to the samples as well as a slow release of fertilizer. Oil was applied to the
samples. Runoff was then collected and measured for oil concentrations. It was found
that the effluent contained negligible amount of oil concentration.

4.4 Passive or Active Mitigation Systems

Pervious concrete pavement can not only handle the surface area runoff from the
pavement, it can also be designed to handle surrounding runoff. Local jurisdictions often
require the pervious pavement to handle not only the given footprint of the pervious
pavement area but also require the drainage of runoff from buildings, construction areas,
etc. The latter case has been deemed as an active mitigation system for pervious concrete
pavements while the former has been classified as passive (NRMCA 2004).
 A passive mitigation system essentially reduces the quantity of impervious
surfaces by replacing it with a permeable one. The design is limited to only capturing
and handling the amount of rainwater over the surface area, not taking into account the
surrounding topography, buildings, site, or other non-permeable areas (NRMCA 2004).
An active mitigation system on the other hand, is just the opposite. Certain
jurisdictions may require the use of pervious concrete to handle stormwater under its own
footprint as well as handle a considerable portion of runoff from other areas. Those other
areas might include buildings, adjacent impervious surfaces including delivery areas,
dumpster areas, heavy traffic areas, traffic islands, and buffer zones. By incorporating all
of these areas into the design, the active mitigation system can minimize the overall
footprint of the developed site.

4.5 Material Properties

Aggregate
The standard type aggregate for use in pervious concrete is typically crushed
stone or river gravel. Typical sizes are from 3/8 in. to 1 in. (Tennis et al 2004). Fine
aggregates are either used sparingly or removed altogether from the mix design. It has
been shown that using smaller aggregates increases the compressive strength of pervious
concrete by providing a tighter bond between coarse aggregate and cement. Using fine
aggregates in the mix design of pervious concrete will also decrease the void space
(Tennis et al 2004). Increasing the percent amount of larger aggregates will increase the
void ratio in pervious concrete, but will decrease the compressive strength (Crouch
2007).
Using recycled aggregates has also been researched. Four mix designs were
studied using 15%, 30%, 50%, and 100% recycled aggregates and compared to the virgin
pervious concrete samples. It was found that samples containing 15% or less recycled
aggregates exhibited almost identical characteristic to the virgin sample (Rizvi et al
2010).
The size of the aggregate also has an important role in pervious concrete. While a
3/4 in. aggregate size allows for greater void space, a 3/8 in. aggregate improves the
workability (Flores et al 2007). The use of 3/4 in. aggregate can decrease settling and
workability. Recent studies have also found that pervious concrete with smaller
aggregates had higher compressive strength (Yang et al 2003). It was noted that the
smaller aggregate sizes allowed for more cementitious material to bind around the
aggregate and hence allowed for greater contact between the aggregate/binder.

Fine Particles
While pervious concrete is considered a “no fines” concrete, a small percentage of
fine particles can be added to increase the compressive strength of the pervious concrete
mix. The inclusion of fine particles has a direct correlation to the paste/mortar strength.
Providing a thicker paste layer around the coarse aggregates results in improved
compressive strength (Schaefer et al 2009). As seen in Figure 2.3, there is a significant
relationship between compressive strength and sand to gravel ratio. When the sand to
gravel ratio is increased to 8 %, the mortar bulks up and increases the strength. When the
sand to gravel ratio increases beyond the 8 % mark, the 7 day compressive strength
begins to fall (Schaefer et al 2009).
Both Europe and Japan have been using smaller aggregates as well as the
inclusion of sand for their mix design (Kajio et al 1998 and Beeldens et al 2003). An
optimization of 10%-20% of fine sand to coarse aggregate has been shown to increase
compressive strength from ~2000 pounds per square inch (psi) to ~2700 psi (Meininger
1988). A slight decrease in permeability correlates to the increase in fine particles.
 Figure 4.3: Relationships between Fine Aggregate and Porosity/Compressive
Strength

Cementations Materials
Portland Type I or II conforming to ASTM C150 or Type IP, IS conforming to
ASTM C-595 have been used as the binder for the aggregates (ACI Committee 522
2006). Additional materials that can be used in the cementitious mix are silica fume, fly
ash, and slag cement (ACI Committee 522 2006 and Tennis et al 2004).
While any potable water can be used for mixing, the amount of water is critical
for the formation of the voids in pervious concrete. Water-to-cement ratios can range
from 0.27 to 0.30 with ratios as high as 0.40. Careful control of water is critical. A mix
design with little water can create a very weak binder. This will create a very dry mix
that is susceptible to spalling and crumbling. A mix design with too much water can
collapse the void space, making an almost impenetrable concrete surface (NRMCA
2004). As seen in Figure 2.4, the specimen in Figure 2.4a has too little water, the
specimen in Figure 2. 4b has the correct amount of water, and the specimen in Figure
2.4c has too much water.
 a.

b.

c.

Figure 4.4: Pervious Concrete With a. Too little Water, b. Appropriate Amount of
Water, c. Too much Water
 A study done by Meininger (1998) demonstrated the relationship between
compressive strength and water-to-cement ratio (see Figure 2.5). The optimal w/c ratio
with the highest compressive strength was found to be between 0.3 and 0.35. Lower w/c
ratios provide poor cohesion between the aggregates. Higher w/c ratios reduce the tensile
capacity by the introduction of capillary pores.

Figure 4.5: Relationship between Water-to-Cement and Compressive Strength

Another study by Chindaprasirt, Hatanaka, Chareerat, Mishima, and Yuasa (2008)

determined that water-to-cement ratio has a direct correlation to cement paste
characteristics, and mixing time of the porous concrete. It was noted that keeping a
relatively low water-to-cement ratio, around 0.2 to 0.3, maintains the continuity of the
paste layer with coarse aggregate. This also aids in the texture and workability of the
pervious concrete. By achieving an even thickness of the paste (150-230 mm) within the
porous concrete mix, this can achieve suitable void ratios of 15-25% and strengths ranges
from 3190 psi to 5656 psi (22-39 MPA).

Admixtures
The use of admixtures in conventional concrete is essential and vital to
performance and workability. High-range water-reducing (HRWR) admixtures are
applied to concrete mixes to affect the set time of concrete (NRMCA 2004). They
require less water and increase the slump of concrete. Caution must be used when
applying HRWR to pervious concrete. Large dosage can cause the cement to segregate
from the aggregate and settle at the bottom of the concrete, forming an impervious layer
of cement (Flores et al 2005).
Latex, a styrene butadiene rubber material which has been used to improve the
cement-aggregate bond (Ramakrishnan 1992), was used to replace a certain amount of
Portland cement to determine its potential application in pervious concrete pavements
(Wang et al 2006). Approximately 10% of Portland cement was replaced with Latex and
it was found that pervious concrete specimens with Latex had, on average, a lower
compressive strength. Although the use of Latex lowered the compressive strength, the
specimens showed an increase in tensile strength, indicating an improved resistance to
cracking.
The uses of hydration controlling admixtures (HCA) were beneficial by slowing
down the rate of hydration. This extended the time before the fresh concrete started to
set, thereby allowing more time to form and finish the concrete surface. Using 5 fl
oz/cwt of the HCA allowed 60 to 90 minutes of added working time (Bury et al 2006).
Viscosity Modifying Admixtures (VMA) may also play a pivotal role on the
performance of pervious concrete. While little has been researched about the use of
viscosity modifiers, the small amount of research has shown that VMA’s can increase
flow of concrete as well as provide ease of compaction and placement. While different
VMA’s can have differing effects on the overall result of pervious concrete, special
attention is needed to determine and verify the correct type and amount prior to
installation (Bury et al 2006).
Void Ratio
Percentage of voids in a sample of pervious concrete can vary significantly. The
amount of void space is dependent on the amount of water needing to permeate through
to the sub-base. Zouahi et al (2000) compared the relationship between percentage of
voids in pervious concrete and compressive strength. Not surprisingly, he found there
was an inverse proportion of compressive strength to void ratio. Generally, pervious
concrete will have a void ratio between 15%-30% with an average of 20%. This
accommodates both the structural requirements and the hydrological requirements of the
design (Tennis et al 2004).
Two testing methods, ASTM D 7063 and ASTM C 140, can be used to test void
ratio or porosity of the pervious concrete specimen. While both methods are acceptable,
ASTM D 7063 can be used to determine the storage capacity of the pervious pavement.
By determining the densities with the use of the displaced water method, the fractional
number of voids can be used to determine the amount of water that can be accessed by
the voids in the concrete (Mata 2008).
A lower void ratio increases the potential for clogging. Joung and Grasley (2008)
devised a test to clog the pervious concrete specimen and measure the permeability. The
clogging procedure applied 50 g of sand and 1 kg of water and thoroughly mixed the two
together. The fluid like material was then poured over the pervious concrete samples.
They were then flushed with clear water. This procedure was repeated five times. The
specimens were then placed in a falling-head permeameter and the permeability was
measured. It was found that a void ratio of 33% or greater was not affected by clogging.
Specimens from 21%-31% showed increased clogging and a decrease in permeability.
While laboratory tests revealed clogging to be a factor with limited void ratios,
the EPA has listed clogging as one of the primary methods of failure for pervious
concrete pavements (US EPA 1999). The Florida Concrete and Products Association has
reported successful removal of clogged pores from pervious pavements in service.
Careful inspection, power washing, and vacuuming/sweeping of loose debris help
maintain the quality and permeability of the pervious concrete system. It has been
reported that much of the potential clogging material in Florida is primarily made up of
sand (Mata 2008).

4.6 Permeability
Concrete
The ability of the concrete to drain runoff water is the key to the success of
pervious concrete. Interconnected voids within the concrete allow the water to penetrate
to the sub-base and remove trace contaminants (Tennis et al 2004). While there is an
inverse relationship between porosity and compressive strength, it is imperative that
proper pervious concrete pavement designs allow for full saturation of the sub-base and
not allow the runoff water to pond within the concrete layer or above the surface
(NRMCA 2004).
While there is no set standard for testing the permeability of concrete, Flores,
Martinez, and Uribe (2007) have devised a testing procedure that evaluates the filtration
ability of pervious concrete cores. The test involves measuring the time it takes for a
given amount of water to pass from the top of a 4 x 8 inch cylinder to the bottom. To
account for bi-directional flow, the pervious concrete cylinder was wrapped in a
waterproof, non-absorbent material.
Another method developed to measure the permeability of pervious concrete has
been the use of the falling head permeameter (Schaefer et al 2006). Figure 2.6 shows a
schematic diagram of the falling head permeameter. The pervious concrete cores are
encased in an impermeable, non-absorbing membrane and connected to a vertical PVC
pipe with open ends on each side, labeled upstream and downstream. To remove the air
voids in the pervious concrete, water was filled in the downstream end up until water
reached the top of the concrete core. Water was then filled on the upstream end.
Equilibrium was allowed to be reached. Water was then added to the upstream side to a
height of 12 in., and fall to about 4 in. The time for the water to drop a predetermined
height was recorded
Sub-base
Once the groundwater has percolated through the pervious concrete, the sub-base
then needs to filter and infiltrate the stormwater. The size, depth, and type of sub-base
material are just as important in reducing stormwater runoff as pervious concrete. The
sub-base beds should have a total volume to capture and store runoff water generated by
a storm in a 24 hr period (Kwiatkowski et al 2007). Undisturbed and uncompacted soil
should be the foundation for the sub-base material. Applying compaction to the soil,
even inadvertent compaction due to construction equipment, can have major implications
on drainage. By compacting the soil, the natural voids within the underlying soil will be
tightened and filtration rate will decrease.
While the thickness and stone base can play a significant role in the permeability,
Tyner, Wright, and Dobbs (2009) explored the different types of treatment for pervious
concrete sub-base as it relates to increased infiltration. Three different types of sub-base
soil treatment were tested: 1. trenched soil and backfilled with stone aggregate, 2. ripped
soil, and 3. boreholes backfilled with sand. A controlled sub-base with no treatment was
also put in place and analyzed. The plots were then fully saturated and infiltration was

measured. It was determined that the use of treatments greatly influenced the infiltration
rate with the trenched treatment having the highest rate (25.8 cm/d) followed by ripped
treatment (10.0 cm/d) and then boreholes (4.6 cm/d) (Tyner et al 2009).
It is important to try to maintain a flat ground level for pervious concrete
pavements. If the slope is too steep, the runoff might collect and exit at the low point of
the pavement. Ponding could occur if the collected stormwater is greater than the
filtration rate (see Figure 2.7)

Figure 4.6: Ponding of Water to Occur on Sloped Pavements

To prevent ponding, it is recommended that the pavement should not exceed a 5%

slope without implementing additional infiltration assistance. Impervious barriers will be
required beneath the sub-base material to prevent the flow of water downhill (NRMCA
2004). Utilizing additional means of helping the sloped pervious pavement drain more
effectively, slopes of up to 16% have been achieved (CCPC 2003). One such method
involved using trenches filled with stone (see Figure 2.8).

Figure 4.7: Sloped Pervious Concrete Pavement with Dug Trenches Filled with
Stone

Figure 4.8: Structural Plan and Elevation of a Sloped Pervious Concrete Pavement
Design

The trenches are dug across the slope, perpendicular to the pavement. A
perimeter drain usually constructed of PVC pipe is installed at the bottom of the trench
and then filled with washed stone. The depth and spacing of the trenches are often
dictated by the slope of the pavement, the soil infiltration rate, and the maximum rainfall
intensity for the site (NRMCA 2004).
4.7 Construction and Maintenance
Sub-base Preparation
Creating a uniform sub-base is a critical component to an effective and efficient
pervious pavement design (Tennis et al 2004). As stated previously, care must be used
when compacting the sub-base soil. Over compaction will decrease the porosity of the
soil and will not allow the pervious pavement to drain well. Under compaction could
allow differential settlement in the pervious pavement which would result in cracking.
Due to the minimal water in the pervious concrete mix, the sub-base must be moist prior
to placement of the pervious concrete. If the sub-base is too dry, the soil will draw water
from the pervious pavement and dry out the pavement prematurely (Tennis et al 2004).

Placement, Consolidation, and Joints

As with conventional concrete, there are a variety of ways to place pervious
concrete. Due to the stiffness of pervious concrete, slump testing has been inadequate for
quality acceptance. It has been suggested that unit weight tests provide the best
measurement for quality control (Tennis et al 2004). Due to the low amount of water and
high evaporation rates, placement should be continuous with rapid spreading and strike
off (Tennis et al 2004). Vibrating and manual screeds should be used to help settle and
level the pervious concrete (see Figure 2.13). Consolidation should then be accompanied
with the use of a steel roller (see Figure 2.14) (ACI Committee 522 2006). It has been

widely accepted that consolidation and compaction can play a very large role in
compressive strength as well as permeability of concrete. It was reported that porosity
varied linearly in concrete slabs 6 in. or greater (Haselbach et al 2006). This was due to
the compaction methods using the steel roller.
Figure 4.9: Mechanical Vibrating Screed

Figure 4.10: Use of a Steel Roller

Figure 4.11: Use of a Rolling Joint Tool

 Once the pervious concrete has been put in place, control joints should then be
cut. Similar to conventional concrete, pervious concrete is subjected to random cracking
due to hydration and shrinkage (Tennis et al 2004). It is recommended that joints should
be spaced at a maximum of 45 feet with a depth of ¼ of the slab thickness (GCPA 1997
and Paine 1992). While saw cutting is possible although not preferred, the standard
method of creating control joints has been with using a rolling joint tool (see Figure 2.15)
(Tennis et al 2004). Since hydration and shrinkage are often imminent right after
placement, joints should be placed soon after consolidation of the pervious pavement
(Tennis et al 2004).

Maintenance
To help prolong the service life, an active maintenance program has shown to be
beneficial in pervious concrete pavements. Over time, dirt and debris can get trapped and
lodged within the voids of the pervious concrete pavement. With the dirt and debris
creating an impervious layer within the pervious concrete pavement, water can then
become trapped. Once this happens, freeze-thaw damage in the pervious pavement is
possible.

Figure 4.13: Clogged Pervious Concrete Pavement

An active maintenance program starts with the initial planning of the site. The
design and layout of the surrounding landscaping should eliminate the potential of flow
of materials onto the pavement surface. Careful construction techniques should also be in
place. Temporarily placing topsoil, mulch, etc. on the pavement should be avoided due
to the potential of these materials seeping into the pervious concrete pavement.
 Once the pervious pavement has been placed into service, an active regiment of
vacuuming and power washing should be implemented. Several tests have shown that
pressure washing of a clogged pervious pavement restored up to 80% of the permeability.
Vacuuming is recommended to be done on an annual basis. This allows the easily
removable debris to be swept before it has a chance to become trapped.

Figure 4.14: Vacuum for Sweeping Pervious Concrete Pavements

Vacuuming should be done prior to power washing. In a research report
sponsored by RMC Research Foundation, testing was done to determine what proper
active maintenance program was optimal to restore initial permeability. Core samples
from various locations in Florida, Georgia, and South Carolina were taken and
permeability was measured prior to remedial actions. Active maintenance in the form of
pressure washing, vacuuming, and a combination of the two was then performed and
found that in each case a 200% increase in permeability was achieved (Chopra et al
2007). It was noted that the pressure washing maintenance did allow potential pollutants
that were trapped and lodged to freely flow to the sub-base.
Visual inspection should also be included as part of the active maintenance
program. By actively evaluating and reviewing pervious pavements specifically after a
heavy rain, problem areas can be easily identified. This can help with identifying
clogged areas prior to a wintertime freeze.
 CHAPTER - 5

MIX DESIGN

5.1 MIX DESIGN

While pervious concrete contains the same basic ingredients as the more common
conventional concrete (ie. aggregate, Portland cement, water, and a variety of
admixtures), the proportioning of ingredients is quite different. One major difference is
the requirement of increased void space within the pervious concrete. The amount of
void space is directly correlated to the permeability of the pavement. With low water to
cement ratio, the need for void space within the mix design, and little to no fine
aggregates, the conventional design of concrete needs to be adjusted accordingly.
Ranges of materials commonly associated with pervious concrete are listed below. These
ranges are based on previous research.
Design Void Content: 15% to 25%
Water to Cement Ratio: 0.27 to 0.33
Binder to Aggregate Ratio: below 0.25
The goal for the final mix design was to provide a strong, durable pervious concrete
design which allowed for adequate drainage of rainwater. Reviewing the literature and
past research, a 15% design void content would have allowed for higher strength and
durability in the pervious concrete samples but not allowed adequate drainage based on
Tamil Nadu peak storm events. A 25% void content would have allowed more than
enough void space in the samples to accommodate a peak storm even in Tamil Nadu but
may not have provided the strength and durability that was required for the research
project.
Taking into account the goals of the project and the literature review, a target void
content of 20% was desired with a water-to-cement ration of 0.3. Prior to the application
of the admixtures, several test mixes were performed to determine an appropriate mix
design for the project. While trying to increase strength and maintaining permeability,
different values of water to cement ratio were tested. Three different water-to-cement
ratios were tested: 0.27, 0.30, and 0.33. Three cylinders, 4 inch diameter by 8 inch tall
were cast for each ratio. During mixing, it was noted that the lowest water-to-cement
ration of 0.27 was very dry. The cylinders were demolded after 24 hours and allowed to
cure in a water tank. After three days, it was visually observed that the lowest water-to-
cement ratio had several loose aggregates not bonded together. Comparing to the
literature review, past research, and the sample mix designs performed, the mix design
noted in Table 3.2 was selected.

Table 5.1: Concrete Mixture Properties

Required Pervious Concrete Mixture Properties

Design Void Content 20.00%
Water to Cement Ratio 0.3
Supplemental Cementitious Material 0

Design for 1 cy of
Required Materials concrete
Weight (lbs) Volume
Coarse Aggregate 2426 53.10%
Fine Aggregate 183 4.10%
Cementitious Material 620 11.70%
Water 181 11.00%
Water Gallons 21.7
Volumetric Void Content 20.00%
Design Unit Weight 126.4 pcf

The standard mix proportions for the mix were as follows:

Cement: Coarse Aggregate: Fine Aggregate: Water which will be equivalent to
1:4.1:0.30:0.30 by weight. The pervious concrete mix design that was used for this
research project was determined from a thorough literature review of past research.
The total amount of concrete to conduct the six tests (Compression Test, Tensile
Test, Permeability Test, Density and Void Test, Freeze-Thaw test, and Abrasion Test)
required is 0.28 cubic yard. Table 3.3 is a breakdown of materials needed per test:
 Table 5.2: Material Quantities

Test
CM DM CF VM
Portland Cement (lbs) 43.4 43.4 43.4 43.4
Coarse Aggregate (lbs) 170 170 170 170
Fine Aggregate (lbs.) 12.81 12.81 12.81 12.81
Water (lbs) 12.67 12.67 12.67 12.67
Delayed Set Modifier (fl oz) X .56 X X
Cellulose Fibers (lbs.) X X .5 X
Viscosity Modifier (fl oz) X X X .56

Mix Procedure
The pervious concrete for the four mixes were prepared in four separate batches
using a rotating drum concrete mixer.

Figure 5.1: Mixing Drum Used

 The coarse aggregate was sieved and all larger aggregates were removed. The
aggregates were then weighed and separated into four different batches. The fine
aggregates were allowed to air dry overnight to remove moisture. They were then
weighed and separated. The rotating drum mixer was cleaned and dried. Water and
admixtures were weighed and placed next to their respective batches. The drum mixer
was started and about 5-10% of the Portland Type I cement and water was added to the
coarse aggregate. The rotating drum was turned on and the materials were mixed for one
minute. The remaining cement, fine particles, water, and aggregate were added to the
rotating drum and mixed. The entire mixture was mixed for three minutes. The mixture
was then allowed to rest for three minutes and then was mixed again for another two
minutes.
The mixture was then reviewed for consistency by taking a handful of pervious
concrete mix and creating a ball. If the aggregate separated and did not maintain the ball
shape, the mixture was considered too dry. If the ball had a lot of paste running off the
aggregate and sticking to the glove, then the mixture was considered too wet. Although
this is subjective, this has been considered a common practice in the industry.
Once the observations were noted, the density and void ratio test was conducted.
The discussion of this test can be found in Chapter 4. The mixtures were then placed in
cylinders or prisms. With the exception of the 6 in. diameter x 12 in. long cylinders, each
cylinder or prism was filled halfway to the top. Each specimen was then rodded 25 times
equally around the sample. The specimens were then filled 1/2 in. above the top and
rodded again 25 times evenly around. With the 6 in. diameter x 12 in. long specimens,
each sample was filled 1/3 to the top and then rodded. The specimens were then struck-
off at the top and covered. After 24 hours, the cylinders or prisms were removed from
their molds and placed in a curing box. The curing box was a wet tank kept at room
temperature. Three technicians were used to help mix and mold all of the specimens.
 CHAPTER - 6
EXPERIMENTAL TESTS AND RESULTS

6.1 Density and Void Ratio

ASTM C1688 has become one of the few accepted tests that can adequately
determine effective pervious concrete mix properties such as density and void content.
This test helps to determine if the freshly mixed concrete will achieve the targeted void
content as specified in the mix design. The test was conducted at the University of Tamil
Nadu and was done by first obtaining a cylindrical steel container with a minimum
capacity of .25 cubic feet. The inside was moistened with a damp towel and excess water
was removed from the bottom. The container was then weighed and the weight recorded
to the nearest gram. The freshly mixed pervious concrete was scooped into the container
and once it was approximately half full, a standard proctor hammer was used to compact
the specimen. The hammer was dropped 20 times evenly around the cylindrical area.
The container was then filled ¼ of an inch above the top lip. The proctor hammer was
used again to compact the specimen using 20 evenly distributed blows. A hand trowel
was used to strike off the top surface of the container and a clean towel was used to wipe
down the sides. The cylinder was then weighed and the weight recorded to the nearest
gram. The weight of the pervious concrete sample was found by subtracting the total
weight of the cylinder and sample from the measured weight of the container.
 Figure 6.1: Apparatus Used for Density and Void Content

The density and void content was found by first determining the theoretical
density of the concrete computed on an air-free basis. This is computed by dividing the
total mass of all materials batched by the sum of the absolute volumes of the component
ingredients in the concrete mix. Densities of the different mix designs of pervious
concrete are noted .
 Table 6.1: Density and Theoretical Density of the Pervious Concrete

Density of the Mix

Control Mix 128.98 pcf
Delayed Set Modifier 127.23 pcf
Viscosity Modifier 128.39 pcf
Cellulose Fiber 130.53 pcf
Theoretical Density of the Concrete:
S.G. Coarse Aggregate 2.71
S.G. Fine Aggregate 2.62
S.G. Portland Cement 3.15
S.G. Fibers 1.1

Coarse Aggregate Mass 2426 lbs

Fine Aggregate Mass 183 lbs
Portland Cement Mass 620 lbs
Water Mass 181 lbs
Fiber Mass 2 lbs

The absolute volumes were determined by taking the quotient of the mass of the
ingredient divided by the product of its relative density times the density of water. The
specific gravities for the coarse and fine aggregates were given by the aggregate supplier.
The Portland cement was assumed to have specific gravity of 3.15 as stated in ASTM C
1688. Equation 1 denotes the theoretical density of the concrete computed on an air-free
basis:

T = Ms/Vs ................................................................................................ Eq.1

To calculate the actual mix density, the mass of the concrete filled container must
be subtracted from the mass of the container and then divided by the volume of the
container. Equation 2 denotes the density of the pervious concrete mix:
D = (Mc-Mm)/Vm ..................................................................................... Eq.2

The void content of the sample was found by the following equation:

U = (T-D)/T x 100 %…………………………………………...………………….Eq.3

The target void content of the mix design was 20%. As shown in Table 4.2, all
four mix designs are within an acceptable range. The cellulose fiber mix had the lowest
void content. This was primarily due to the fibers taking up a small portion of the void
content.
Table 6.2: Calculated Void Content

Void Content:
Control Mix 19 %
Delayed Set
Modifier 20 %
Viscosity Modifier 19 %
Cellulose Fiber 18 %

6.2 Compressive Strength Test

The compressive strength test was performed on all four mix designs. Three
cylinders were cast from each mix design and the average of the compressive strength
was used as the final number. Four different periods were used to determine the rate at
which the cylinders gained strength – Day 7, Day 14, Day 28, and Day 120. The test was
performed at a University of Tamil Nadu Laboratory. The specimens were removed from
the curing box at the day of testing and wiped clean. The diameter of each specimen was
measured at the top, middle, and bottom. The average of the three diameters was used to
calculate the cross-sectional area. Any specimen having a diameter varying more than
2% of any other measured diameter was not used in the compression test. All the
pervious concrete samples met this requirement. The specimens were then placed under
the center ring of the compression machine. The test machine used was hydraulically
powered. The upper bearing block was stationary, while the lower bearing block moved
up to compress the specimen. The upper bearing block was capable of tilting if the top of
the specimen was not completely horizontal. Prior to testing, the surfaces of the testing
machine were wiped clean. The test cylinder was then placed on the lower bearing block
and centered. The load was applied at a rate corresponding to a stress increase between
28 psi/sec and 42 psi/sec. Each specimen was loaded until the load began to decrease
rapidly, and a fracture was clearly evident. The maximum load applied was then
recorded. The procedure was repeated at the interval of days noted earlier.

Figure 6.2: Pervious Concrete Specimen in Compression Testing Machine

 Table6.3: 7Day Compressive Strength Result

Control Mix 1 25640 lbs 2041.401 psi

Control Mix 2 24020 lbs 1912.42 psi
Control Mix 3 20200 lbs 1608.28 psi
1854.034 psi

Table6.4: 14Day Compressive Strength Result

Control Mix 1 26240 lbs 2089.172 psi

Control Mix 2 28050 lbs 2233.28 psi

Control Mix 3 39020 lbs 3106.688 psi

2476.38 psi

Table6.5:28DayCompressive Strength Results

Control Mix 1 29520 lbs 2350.318 psi

Control Mix 2 37840 lbs 3012.739 psi

Control Mix 3 31150 lbs 2480.096 psi

2614.384 psi

Table6.6:120Day Compressive strength Result

Control Mix 1 42020 lbs 3345.541 psi

Control Mix 2 38880 lbs 3095.541 psi

Control Mix 3 28570 lbs 2274.682 psi

2905.255 psi

contain the results of the 7, 14, 28, and 120 day compressive strength results
respectively. Each specimen was loaded until the load began to decrease rapidly and a
well-defined fracture appeared.
The compressive strength was calculated by dividing the final maximum load
recorded by the cross-sectional area of the cylindrical specimen. If the specimens had a
Length-to-Diameter ratio less than 1.75, the compressive strength calculated must be
modified with a correction factor. If the Length-to-Diameter ratio is greater than 1.75, no

correction factor is needed. Since the ratio for all specimens exceeded 1.75, no
correction factor was used.
The average 28 day compressive strength varied from 2048 psi to 3227 psi. The
low variation in the compressive strength can be attributed to the same method of
compaction of the specimens. Each specimen was compacted at two lifts – one at the
mid height and the other at the top. It has been discussed that for pervious concrete
samples there is a high degree of correlation between compressive strength and the
method of compaction. Due to the open voided structure of the pervious concrete, the
more compaction each sample receives, the more these voids tend to close. The
relationship between compressive strength and void ratio .

3500

3000

2500
Compressive Strength in Psi

2000
R 2 = 0.9548

1500

1000

500

0
17 18 19 20
Void Content in Percent

Figure 6.3: Correlation between Void Content and Compressive Strength

6.3 Split Cylinder Test

A split tensile strength test was performed for all samples cured at 28 days as
specified in ASTM C496. While there have not been any standard tests adopted by
ASTM to provide a direct measurement of the tensile strength of pervious concrete,
ASTM C 496 has been used in a wide variety of other research.
This test measures the tensile strength of a concrete sample by compressing a
cylinder through a line load applied along its length. This test can be completed in a
standard compression testing machine. The test was conducted on the same machine as
the compressive test at the University of Tamil Nadu.
A uniform tensile stress is created over the cylinder’s diameter along the plane of
loading. The maximum tensile stress occurs at the center of the cylinder. ASTM C496
indicates that the maximum tensile stress can be calculated based on Equation 4. In this
equation, P is the load applied to the cylinder, l and d are the length and diameter, and T
is the tensile stress.
T=2P/πld ..................................................................................................Eq.4.
For the pervious concrete specimens, each sample was removed on day 28 of
curing from the curing box and wiped clean. Two diagonal lines were then drawn at the
center of each specimen with a permanent marker. The diameter of the specimen was
measured at three locations, top, middle, and bottom and the results were averaged. A
wooden bearing strip 1/8 in. thick was placed on the bottom bearing block. The pervious
concrete specimen was then placed on the bearing strip, aligned with the center. The top
bearing strip was aligned with the pervious concrete sample. The bottom bearing block
was then hydraulically elevated. The machine was started at the loading rate of 150
psi/min. When the specimen broke, the load was recorded.

Figure 6.4: Split Tensile Strength Test with Bearing Strips Prior to Loading
 Table 6.7: Tensile Strength Results

Control Mix 1 4200 lbs 334.3949 psi

Control Mix 2 3300 lbs 262.7389 psi
Control Mix 3 3600 lbs 286.6242 psi
294.586 psi

Not surprisingly, the split tensile strength was considerably low with cellulose
fibers exhibiting the highest amount of tensile stress. Figure 4.5 shows the relationship
between compressive strength and tensile strength. Clearly, there is no real correlation
between compressive strength and tensile strength of the pervious concrete samples.

450

400

350

300
Tensile Strength in psi

250 Control Mix

DM Mix
VM Mix
200
CF Mix

150

100

50

0
0 500 1000 1500 2000 2500 3000 3500
Comprssive Strength in psi

Figure 6.5: Comparison between Compressive Strength and Tensile Strength

6.4 Permeability Test

Permeability was determined using the falling head method through a
permeameter. At the time of testing, there were no approved standards for measuring
permeability in pervious concrete samples. The falling head apparatus has been used
successfully at the National Ready Mix Concrete Association (NRMCA) with past
pervious concrete samples. NRMCA engineers were consulted and several
demonstrations were performed.The test originated from ASTM 522 as an acceptable
means of measuring permeability in pervious concrete. The falling head method has been
used successfully in past research. The test was conducted at Eastern Testing and
Inspection Laboratory in Frederick, Tamil Nadu. Samples used in the permeability test
were four inches in diameter and eight inches in length. Each sample was removed from
the curing box after 28 days of curing and wiped clean. The sample was then wrapped
from top to bottom in a flexible sealing gum to prevent water leakage along the sides of
the sample. A clear PVC tube was connected to the top of the sample by an oversized
rubber hose clamp. The clamps were screwed tight and checked for leakage. A clear

PVC pipe was used to allow the water height to be read as it dropped down the sample.
Standard PVC pipes were used for the remainder of the apparatus. A separate oversized
rubber hose clamp was used to connect the bottom of the specimen to the standard PVC
pipe. A rubber stopper was used at the end of the standard PVC pipe. Once all the pieces
were setup, the stopper was put in and the apparatus was filled with water. No leakage
was apparent. The rubber stopper was removed and the specimen was allowed to drain.
This allowed the pervious concrete specimen to become fully saturated prior to testing.
Once the water height reached equilibrium, the rubber stopper was applied and water was
added to the clear PVC pipe. Markings for the water height were noted on the clear PVC
pipe.

Figure 6.6: Materials Used for Falling Head Permeability

 Figure 6.7: Assembled Falling Head Permeability Test

The rubber stopper was released and the time was recorded. The coefficient of
permeability (k) was determined by Equation 5:

k = (aL/At)LN(h1/h2)… ............................................................................................. Eq.5

Where k = coefficient of permeability (in/hr), a = cross sectional area of the standpipe

(in2), L = length of the specimen (in), A = cross sectional area of the specimen (in 2), t =
time for water level to reach from h1 to h2 (sec.), h1 = initial water level (in), and h2 =
final water level (in). Table 4.8 contains the results of the permeability tests.
 Table 6.8: Permeability Results

Permeability
Date of Test 10/24/2010 in/hr.
Control Mix 1 417
Control Mix 1b 400
Control Mix 1c 412

All of the specimens that were tested had very similar permeability results.
Permeability is highly correlated to void ratio; and since the void ratios varied from 18%-
20%, the permeability results were also fairly similar as expected. Permeability
coefficients for actual field conditions would be different from the laboratory results due
in part to potential clogging of the pervious pavement, underlying soil conditions, and
compaction methods which are all factors that would affect the permeability coefficient .
CHAPTER-7

RESULTS AND DISCUSSION

7.1 Fiber Results

Not surprisingly, cellulose fibers had an important impact on the durability of
pervious concrete. Although the traditional polypropylene fibers have shown great
promise in pervious concrete, it was unclear how the cellulose fibers would compare.
The wet mix was very comparable to the control mix. The ease at which the pervious
concrete was removed from the mixer and molded was very similar to the control mix.
This was to be expected since the fibers did not affect the overall chemical properties of
the cement. The use of small fibers also helped in reducing the problematic issue of
fibers balling in the mix.
The results of the compressive strength were also very similar to the control mix.
The greater advantage of the cellulose fibers came from the tensile strength and the
freeze-thaw test. The tensile strength for the cellulose fibers had the highest reported
value as expected. The addition of cellulose fibers to the cementitious material stiffens
the matrix. This stiffening not only reduces the cracking due to both plastic and drying
shrinkage, but also helps with ductility. The fibers help bridge the gap between
aggregates and create a strong matrix of interwoven cellulose fibers.
The freeze-thaw resistance was the highest of all the mixes, providing a very
strong resistance. The fibers played a very strong role is resisting the thermal expansion
and contraction due to the repetitive freezing and thawing. Regardless of the type of test
(dry, 50% saturated, 100% saturated), the cellulose fiber mix had the least amount of
mass loss.
 CHAPTER-8
CONCLUSIONS
Although limited in its applications, pervious concrete has the potential to help
mitigate many of the urban storm water quality issues. Lack of extensive research on
pervious concrete has led to some misunderstanding and narrow focus on the use of
pervious concrete. One of the objectives of this research was to develop a preliminary
pervious concrete specification for Tamil Nadu conditions. Several admixtures have
been tested as part of this research with the objective of increasing strength, durability
and workability of pervious concrete. Improved strength, durability and workability
would lead to a wider application of pervious concrete.
The types of admixtures that were tested as part of this research included delayed
set modifier, viscosity modifier, and cellulose fibers. These three admixtures were
selected based on the potential of increasing strength, durability, workability, or a
combination of the three.
The ability to discharge, place, and finish pervious concrete within a relatively
short time span is a major concern for concrete producers. The relatively short working
time window with pervious concrete often leads to a very fast paced, labor intensive
effort. Incorporating a delayed set modifying admixture into the pervious concrete mix
design inevitably allows a longer working window for placement.
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