Wang et al, submitted to NRMCA Concrete Technology Forum: Focus on Pervious Concrete, May 24-25, 2006, Nashville, TN
Development of Mix Proportion for Functional and Durable Pervious Concrete
Wang, K.1, Schaefer, V. R.2, Kevern, J. T.3, and Suleiman, M.T.4
Abstract
Portland cement pervious concrete (PCPC) mixes made with various types and amounts of
aggregates, cementitious materials, fibers, and chemical admixtures were evaluated. Porosity,
water permeability, strength, and freezing-thawing durability of the concrete were tested. The
results indicated that the PCPC made with single-sized coarse aggregates generally had high
permeability but not adequate strength. Addition of a small amount of fine sand (approximate
7% by weight of total aggregate) to the mixes significantly improved the concrete strength and
freezing-thawing resistance while maintaining adequate water permeability. Addition of a small
amount of fiber to the mixes increased the concrete strength, freezing-thawing resistance as well
as void content. Based on these results, performance-based criteria are discussed for
proportioning functional and durable PCPC mixes.
Introduction
Portland cement pervious concrete (PCPC) is increasingly used in the United States because of
its various environmental benefits such as controlling storm water runoff, restoring groundwater
supplies, and reducing water and soil pollution (Youngs 2005 and Kajio et al. 1998). Due to the
permeability requirement, PCPC is typically designed with high void content (15-25%). Singlesized aggregate is commonly used to achieve such void content (Tennis et al. 2004). Because of
the high void content, PCPC generally has low strength (800-3000 psi), which not only limits its
application in cold weather regions but also is responsible for various distresses in and failures of
the related structures. Lately, PCPC has been considered for some pavements in cold weather
regions (such as Iowa and Minnesota). However, limited research has been conducted to
characterize PCPC mix proportions and to investigate its serviceability under cold weather
conditions. The present study was conducted to fill this gap and to spur PCPC applications.
In this paper, PCPC mixes were designed with various types and amounts of aggregates,
cementitious materials, fibers, and chemical admixtures. Porosity, water permeability, strength,
and freezing-thawing (F-T) durability of the concrete samples were tested. The effects of these
materials and mixture proportions on the PCPC performance/ properties were explored. The
following sections describe the detailed experiments, test results, and major findings.
1
Assistant Professor, Civil, Construction, and Environmental Engineering, Iowa State University, Ames,
IA,kejinw@iastate.edu
2
Professor, Civil, Construction, and Environmental Engineering, Iowa State University, Ames, IA,
vern@iastate.edu
3
Research Assistant, Civil, Construction, and Environmental Engineering, Iowa State University, Ames, IA,
kevernj@iastate.edu
4
Research Assistant Professor, Civil, Construction, and Environmental Engineering, Iowa State University, Ames,
IA, suleiman@iastate.edu
1
Wang et al, submitted to NRMCA Concrete Technology Forum: Focus on Pervious Concrete, May 24-25, 2006, Nashville, TN
Experimental Work
Materials.
Type I/II cement was used in all mixes, and the cement had a fineness of 384
m2/kg and a specific gravity of 3.15.
A single-sized limestone (3/8”LS, which passed the ½” (12.5 mm) sieve but retained on the 3/8”
(9 mm) sieve), and two single-sized river gravels (3/8”RG, which passed ½” (12.5 mm) sieve but
retained on 3/8” (9 mm) sieve, and #4RG, which passed 3/8” (9 mm) sieve but retained on No.4
(4.75 mm) sieve) were used as coarse aggregate. The properties of the coarse aggregate are
summarized in Table 1, where unit weight and voids tests were performed based on ASTM C29,
and the specific gravity and absorption tests were performed based on ASTM C127.
Table 1: Properties of coarse aggregates
Aggregate
3/8”RG
#4RG
3/8”LS
3/8”LS*
Unit weight (lb/ft3)
102.6
99.6
86.5
88.8
Voids (%)
37.3
38.5
43.5
44.2
Abrasion mass loss (%)
14.4
14.4
46.1
32.9
Specific gravity
2.62
2.62
2.45
2.55
Absorption
1.1
1.1
3.2
3.2
Note: 3/8”LS* was from the same source but received at a different time and used for Mix 3A only
To improve concrete strength, a small amount of river sand was incorporated in the PCPC mixes.
The sand had a fineness modulus of 2.9, specific gravity of 2.62, and absorption of 1.1%.
To improve the cement-aggregate bond and the F-T durability, a styrene butadiene rubber (SBR)
latex was used. The SBR latex is approved by the Federal Highway Administration for latex
modified concrete use in bridge deck overlays (Ramakrishnan 1992). The SBR used had a solid
content of 48% and pH of 10. Various amount of polypropylene fiber is also used in selected
PCPC mixes.
Air entraining agent (AEA) and high-range water reducer (HRWR) were used in the mixes that
did not contain latex. The specific gravity and pH were 1.01 and 10 for the AEA (Everair plus)
and 1.07 and 7.8 for the HRWR (Glenium 3400 NV), respectively.
Mix Proportions.
The mix design was divided into two parts. Part I was designed to
investigate the effects of aggregate size and type on the void ratio and strength of pervious
concrete, and Part II was to investigate the effects of sand, latex, fiber and admixtures (AEA and
HRWR) on PCPC properties. All concrete mix proportions used are summarized in Table 2. The
slump of the mixtures was between 0 in. to ½ in. (0 cm and 1.27 cm ).
2
Wang et al, submitted to NRMCA Concrete Technology Forum: Focus on Pervious Concrete, May 24-25, 2006, Nashville, TN
Part II
Part I
Table 2: Mix proportions
Mix
C. Agg.
Cement
(lb/yd3)
1
2
3
1A
1B
2A
2B
2C
2D
2E
3/8”RG
#4RG
3/8”LS
3/8”RG
3/8”RG
#4RG
#4RG
#4RG
#4RG
#4RG
600
600
600
571
520
571
520
520
542
485
2F
2G
2H
3A
3B
#4RG
#4RG
#4RG
3/8”LS*
3/8”LS
600
600
571
571
571
Latex
Solid
(lb/yd3)
----52
-52
52
29
86
-52
C. Agg.
(lb/yd3)
Sand
(lb/yd3)
Water
(lb/yd3)
Fiber
(lb/yd3)
w/c
168
168
168
162
162
154
114
154
116
114
114
114
AEA/HRA
(oz/100 lb
PC)
2.15/4.25
2.15/4.25
2.15/4.25
2.15/4.25
-------
2700
2700
2700
2500
2500
2500
2500
2500
2500
2500
----
162
-----------
0.27
0.27
0.27
0.27
0.22
0.27
0.27
0.22
0.22
0.22
2700
2700
2500
2500
2500
168
168
168
162
162
154
154
126
2.15/4.25
2.15/4.25
2.15/4.25
2.15/4.25
--
0.5
1.5
1.5
---
0.27
0.27
0.27
0.27
0.22
168
168
168
--
Specimen Preparation.
To improve the bond between cement paste and aggregate, the
following mixing procedure was used:
1. A small amount of cement (<5% by mass) was mixed with aggregate for about 1 minute
2. The remaining cement and water (with or without admixtures) was added the mixer
3. The mixture was then mixed for three minutes, rested for three minutes, and then mixed
for another two minutes before casting.
All specimens were placed by rodding 25 times in three layers along with applying a vibration
for five seconds after rodding each layer. The samples were demolded after 24 hours and cured
in a fog room according to ASTM C192.
4 in. by 8in. (10cm by 20cm ) cylinders were used for both compression and splitting tensile
strength tests. Before compression testing, the cylinders were capped using a sulfur capping
compound following ASTM C617. 3 in. by 6in. (7.5cm by 15cm ) and 3 in. by 3in. (7.5cm by
7.5cm ) cylinders were used to perform the void ratio and permeability, respectively. 4in. by 4in.
by 16in. (7.5cm by 7.5cm by 40cm ) beams were used for F-T tests. Three samples were used for
each test.
3
Wang et al, submitted to NRMCA Concrete Technology Forum: Focus on Pervious Concrete, May 24-25, 2006, Nashville, TN
Test Methods.
In the present study, unit weight and slump tests were performed
for fresh concrete based on ASTM C 138 and C143, respectively. PCPC Void ratio was tested at
7-days, compressive strength at 7, 21, and or 28 days, splitting tensile strength and water
permeability at 28 days. Compressive strength tests were performed according to ASTM C39.
Splitting tensile strength tests were performed based on ASTM C496.
The void content of the PCPS samples was determined by taking the difference in weight
between a sample oven dry and under water and using Equation 1 (Park and Tia, 2004).
W − W1
Vr = [1 − ( 2
)]100(%)
(1)
ρ w Vol
Where: Vr = total void ratio, %; W1 = weight under water, lb (kg); W2 = oven dry weight, lb
(kg); Vol. = volume of sample, ft3 (cm3); and ρw = density of water, lb/ft3 (kg/cm3).
Permeability of the PCPC samples was determined using the falling head permeability test
apparatus illustrated in Figure 1. A sample was confined in a membrane and sealed in a rubber
sleeve. Four different water heights, which represented the values that a pavement may
experience, were applied to the sample, and the time for the water to drain out of the sample was
then recorded. For each water height, the permeability coefficient (k) was determined using
Equation 2. The average value resulting from the different water heights was defined as the
permeability coefficient of the sample.
⎛h ⎞
aL
k=
LN ⎜⎜ 1 ⎟⎟
(2)
At
⎝ h2 ⎠
Where k = coefficient of permeability, cm/s; A = cross sectional area of the standpipe, in.2
(cm2); L = length of sample, in. (cm); A = cross sectional area of specimen, in.2 (cm2); t =
time in seconds from h1 to h2: h1 = initial water level, in. (cm); and h2 = finial water level, in.
(cm).
Figure 1: Water permeability test setup
Selected concrete mixes, with adequate void ratio and 7-day compressive strength, were further
tested for freeze-thaw resistance using ASTM C666 ⎯ procedure A, in which the samples were
4
Wang et al, submitted to NRMCA Concrete Technology Forum: Focus on Pervious Concrete, May 24-25, 2006, Nashville, TN
frozen and thawed in wet conditions. The test was completed when the sample reached 300
cycles or 15% mass loss. Mass loss was tested every 20 to 30 cycles.
Results
Effect of Coarse aggregate Type and Size on PCPC Properties.
Table 3 presents the
properties of the PCPC mixes designed in the Part I study, where different types and sizes of
coarse aggregates were used in a typical PCPC mix (Table 2). As observed in Table 3, when
single-sized coarse aggregate was used, the desirable void content (≥15%) was easily achieved.
For the given mix proportion, PCPC made with river gravel had lower void content but high
compressive strength than that made with limestone. For given river gravel, smaller size
aggregate reduced the void content but increased 7-day compressive strength of the PCPC.
However, in this group (the PCPC without sand), the highest strength was only 2500 psi (17.3
MPa ) at 28 days - the strength of the PCPC made with #4RG.
Table 3: Properties of PCPC mixes without sand (w/c=0.27, cement content 355.8 kg/m3)
Compressive Strength (psi)
Unit
Void
Splitting
Water
Mix
C. Agg.
Weight
Content
Strength Permeability
7-day 21-day
28-day
(lb/ft3)
(%)
(psi)
(in./sec)
116.9
1
3/8”RG
28.8
1771
2
#4RG
117.5
25.3
2100
2385
2506
287
0.10
3
3/8”LS
104.1
33.6
1396
1663
1722
205
0.57
3
Notes: 1 kg/m =0.0624 lb/cf, 1 MPa=145 psi; 1 cm/sec=1417.3 inch/hour.
Effect of Sand on PCPC Properties.
It was observed in the Part I study that under
vibration, some cement paste was accumulated at the bottom of the samples, which implied that
the cement content used in the mixtures might be higher than necessary. Therefore, in the Part II
study, cement content of PCPC was reduced from 600 lb/yd3 to 571 lb/yd3, while the water-tocement ratio (w/c) was kept the same. River sand was used to replace approximate 7% (by
weight) coarse aggregate in order to improve the concrete strength. Table 4 presents the
properties of the PCPC mixes with the sand replacement.
Table 4: Properties of PCPC mixes with sand (w/c=0.27, cement content 338.4 kg/m3)
Compressive Strength (psi)
Unit
Void
Splitting
Water
Mix
C. Agg.
Weight
Content
Strength Permeability
7-day 21-day
28-day
(lb/yd3)
(%)
(psi)
(in./hr)
130.9
1A
3/8”RG
20.5
3262
---694
2A
#4RG
127.7
18.3
3299
3380
3661
421
142
3A
3/8”LS
119.8
23.0
3229
--
--
--
326
When compared with Mixes 1, 2 and 3 (Table 3), mixes 1A, 2A, and 3A (Table 4) all had
significantly improved strength. Especially, the 7-day compressive strength increased from
1,390-2,100 psi (9.6-14.5 MPa) to 3,220-3,290 psi (22.2-22.7 MPa). This early-age strength
improvement may have a great impact on the F-T durability of PCPC in field. It should be noted
that the differences in the properties of mixes 3 and 3A might partially result from the different
3/8”LS properties (see Table 1).
5
Wang et al, submitted to NRMCA Concrete Technology Forum: Focus on Pervious Concrete, May 24-25, 2006, Nashville, TN
Although the void content was reduced due to the introduction of fine sand in the mixtures, all
void content values listed in Table 4 were still within an acceptable range (>15%) for PCPC
applications. In other words, although the permeability of Mix 2A decreased from 354 in./hour
to 141.7 in/hour (from 0.25 cm/sec to 0.1 cm/sec) when compared with Mix 2, this permeability
value is still higher than the maximum requirement to drain the maximum 25 year-24 hour storm
across the United States (i.e., 12 inch (30.5 cm) (USDA 1986).
Effect of Latex on PCPC Properties.
To improve the PCPC properties, approximate 10%
latex solid (by weight of cement) was used into selected mixes. Due to the consideration of the
material cost, the latex was used to replace the same amount of cement. As a result, the cement
content of the PCPC mixes reduced from 571 lb/yd3 to 520 lb/yd3. Water-to-cement ratio (w/c)
also reduced from 0.27 to 0.22 for the latex modified PCPC to reach given slump. Table 5
presents the properties of the PCPC mixes made with the sand and latex. Probably due to the less
cement used, the PCPC mixes with latex (Table 5) had lower compressive strength than the
mixes without latex (Table 4). However, even though less cement was used, the PCPC mixes
with latex still had higher splitting tensile strength than the mixes without latex. This indicates
that the addition of latex in PCPC might improve the concrete cracking resistance.
Table 5: Properties of PCPC mixes with sand and latex (w/c=0.22, cement content 308.2 kg/m3)
Compressive Strength (psi)
Unit
Void
Splitting
Water
Mix
C. Agg.
Weight Content
Strength Permeability
7-day
21-day
28-day
(lb/yd3)
(%)
(psi)
(in./hour)
127.3
1B
3/8”RG
20.2
2641
-2924
-340
2C
#4RG
126.8
19.0
2969
3313
3349
453
255
3B
3/8”LS
117.4
25.7
2483
--
--
--
666
Table 6 presents the effect of amount of latex on PCPC properties, where latex was again used
for cement replacement, rather than addition. As observed in the table, the void content of the
PCPC decreased with the increased amount of latex replaced for cement. The optimal amount of
latex appeared to be 10% based on the consideration of the concrete strength and permeability.
Mix
Table 6: Properties of PCPC mixes with different amount of latex (w/c=0.22)
Cement
Unit
Void
Compressive Splitting
Water
Latex
Content Weight Content
Strength
Strength Permeability
Solid
(lb/yd3)
(lb/ft3)
(%)
(psi)
(psi)
(in./hour)
(lb/yd3)
2D
29
542
120.3
26.0
1307
--
--
2C
52
520
126.8
19.0
2969
453
255
2E
86
485
132.2
14.1
2735
--
57
Effect of Fiber on PCPC Properties.
Table 7 presents the effect of fiber addition on
PCPC properties, where Mixes 2F and 2G had no sand and Mix 2H had 7% sand for coarse
aggregate replacement. Generally, addition of the fiber in PCPC slightly increased the void
content and significantly increased the permeability of the concrete. More importantly, it
6
Wang et al, submitted to NRMCA Concrete Technology Forum: Focus on Pervious Concrete, May 24-25, 2006, Nashville, TN
improved the splitting tensile strength of concrete, which in turn enhanced the concrete F-T
durability.
Table 7: Properties of PCPC mixes with fiber (w/c=0.27, cement content 308.2 kg/m3)
Splitting
Water
Compressive Strength (psi)
Fiber
Unit
Void
3
Mix
Strength Permeability
(lb/yd )
Weight Content
7-day
21-day
28-day
(psi)
(in./hour)
(lb/yd3)
(%)
2F
.05
120.4
18.9
2587
2941
3106
348
383
2G
1.5
119.4
22.1
2601
2765
3106
358
964
2H
1.5
122.5
19.0
2988
3220
3849
353
425
F-T Durability Test Results.
As mentioned before, only selected concrete mixes that had
adequate void ratio and 7-day compressive strength were tested for F-T durability using ASTM
C666 ⎯ procedure A. Due to its high permeability, field PCPC is rarely in a saturated condition.
The investigators have noted that ASTM C666 method may not appropriately simulate the field
PCPC condition. However, it is believed that this simple, rapid test method simulates the
extreme case that PCPC might experience, and the method is suitable for a comparison study of
the PCPC F-T durability.
Mix
1A
2
2A
2C
2F
2G
2H
3
3A
3B
Table 8: Summary of F-T test results
Descriptions
F-T cycles to failure
3/8” RG-7% sand
136
#4 RG
153
#4 RG-7% sand
>300, 2.1%weight loss at 300 cycles
#4 RG-7% sand-10% latex replacement
216
#4 RG -0.30 kg/m3 fiber
201
#4 RG -0.89 kg/m3 fiber
181
#4 RG-7% sand-0.89 kg/m3 fiber
Test is in progress; less weight loss than sample Mix 2A
3/8” LS
196
3/8” LS-7% sand
110
3/8” LS-7% sand-10% latex
110
Table 8 summarizes the F-T test results of the PCPC mixes presented in the paper. Among these
mixes, Mix 2H (with #4RG, 7% sand, and 1.5 lb/yd3 fiber) is currently showing the highest F-T
resistance, which had 0.4% weight loss after subjected to about 180 F-T cycles. Mix 2A (with #4
RG, 7% sand) is the second to the highest, which had 0.8% weight loss at 180 F-T cycles and
2.3% weight loss at 300 F-T cycles. Mix 2C (with #4RG, 7% sand, and 10% latex replacement)
comes to the third, which reached 15% weight loss at 216 F-T cycles. These results imply that
when properly designed and constructed, PCPC can have an excellent serviceability under cold
weather conditions.
Discussion
Figures 2-7 illustrate the relationships
Relationships among the PCPC Properties.
among the PCPC properties tested. Most of the relationships are similar to those of conventional
concrete.
7
Wang et al, submitted to NRMCA Concrete Technology Forum: Focus on Pervious Concrete, May 24-25, 2006, Nashville, TN
22
140
3
Unit Weight (kN/m ) = 24.19 - 0.2177 * Void Ratio
Unit Weight (kN/m3)
R2 = 0.92
130
20
125
19
120
18
115
Unit Weight (pcf)
135
21
110
17
105
16
10
15
20
25
30
35
Void Ratio (%)
Figure 2: Relationship between unit weight and void content
3000
y = 13.257e0.1579x
R2 = 0.6522
Water Permeability (in./hr)
2500
2000
1500
1000
500
0
10
15
20
25
30
35
Void Content (%)
Figure 3: Relationship between permeability and void content
4,000
No. 4 sieve
3/8 inch sieve
7-day Compressive Strength (psi)
3,500
1/2 inch sieve
3,000
2,500
2,000
1,500
1,000
500
0
0.1
0.2
0.3
0.4
0.5
0.6
Aggregate Size (in.)
Figure 4: Relationship between coarse aggregate size and PCPC 7-day Strength (River Gravel)
8
3500
24
22
3000
20
18
2500
16
4.75 mm (No. 4), RG
9.5 mm (3/8 in.), RG
4.75 mm (No. 4) PG
14
12
2000
Best FIt
10
15
20
25
4000
Strength (MPa) = 49.95 - 1.181 * Void ratio
2
R = 0.97
24
3500
3000
20
2500
16
2000
9.5 mm (3/8 in.)
12
Best Fit
1500
8
1500
10
28
20
30
22
24
26
28
30
32
34
36
Void ratio (%)
Void Ratio (%)
(a) river gravel and pea gravel
(b) crushed limestone
Figure 5: Relationship between void content and 7-day compressive strength
28-day Splitting Strength,
psi
500
450
R2 = 0.68
400
350
300
250
200
150
100
1000
2000
3000
4000
28-day Com pre s s ive Stre ngth, ps i
Figure 6: Relationship between compressive and splitting strength
350
# of F-T Cycles to Failure
350
300
250
200
150
100
50
0
1000
2000
3000
4000
300
250
200
150
100
50
0
100
200
300
400
28-day Splitting Stre ngth, ps i
28-day Com pre s s ive Stre ngth, ps i
(a) F-T durability vs. compressive strength
(b) F-T durability vs. splitting strength
Figure 7: Relationship between strength and F-T durability
9
500
7-day compressive strength (psi)
26
7-day compressive strength (MPa)
4000
Strength (MPa) = 33.45 - 0.725 * void ratio
2
R = 0.73
7-day compressive strength (psi)
28
# of F-T Cycles to Failure
7-day compressive strength (MPa)
Wang et al, submitted to NRMCA Concrete Technology Forum: Focus on Pervious Concrete, May 24-25, 2006, Nashville, TN
Wang et al, submitted to NRMCA Concrete Technology Forum: Focus on Pervious Concrete, May 24-25, 2006, Nashville, TN
Figure 2 shows that unit weight of the PCPC studied decreased linearly with void content. Figure
3 illustrates that the permeability of the concrete increased exponentially with the concrete void
content. As a result, the unit weight test can serve as a simple, quick quality control test in field
to ensure proper void content or permeability of the concrete.
Figures 4 and 5 demonstrate the relationships between aggregate size, void content, and 7-day
compressive strength of PCPC. There is a trend (Figure 4) that 7-day compressive strength of
PCPC decreases with increased coarse aggregate particle size, which is similar to what is
observed in conventional concrete and largely due to the weak interfacial transition zone
between the cement paste the large size aggregate. Because of the reduced effect cross section
area, the 7-day compressive strength of PCPC also decreases with the void content of the
concrete (Figure 5).
Figure 6 illustrates an acceptable linear relationship (R2=0.74) between the 28-day compressive
and splitting tensile strength of the PCPC tested. If all the test data are considered, there is no
clear relationship between the concrete strength and F-T durability (Figure 7). However, if one
data point is taken away (Mix 3, in hollow), Figure 7b demonstrates a good relationship between
the PCPC splitting/tensile strength and F-T durability. Therefore, the splitting tensile strength
test results can serve as preliminary evaluations for the F-T resistance of PCPC.
PCPC Mix Design Criteria and Considerations.
The mix design criteria and
procedure for PCPC are under development. In the consideration of PCPC function (permeable)
and application (carrying traffic loads and exposed to a mild or cold weather condition),
permeability, strength, and F-T durability of PCPC should be considered simultaneously in the
concrete mix design. Table 9 summarizes the related PCPC properties from literature.
Table 9: PCPC properties from literature
Void
Ratio
Unit Weight
lb/ft3
Permeability
in/hour
28-day
Compressive
Strength
Flexural
Strength
(%)
(kg/m3)
(cm/sec )
psi (MPa)
psi (MPa)
15 to 25
100 - 125
(1602 -2002)
288 -756
(0.203-0.533)
15 to 35
NA
NA
United States
800 -3000
(5.5 -20.7)
NA
150- 550
(1.03 -3.79)
363- 566
(2.50 -3.90)
Reference
Tennis et al. 2004
Olek and Weiss 2003
International
19
NA
118- 130
NA
20 to 30
(1890-2082)
NA
NA
NA
11 to 15
NA
NA
36-252
(0.025-0.178)
18 to 31
NA
NA
3771 (26.0)
2553 -4650
(17.6-32.1)
638 (4.4)
561 – 825
(3.87- 5.69 )
Beeldens et al. 2003
2756 (19.0)
NA
606- 1085
(4.18 -7.48 )
Tamai and Yoshida 2003
NA
Park and Tia 2004
NA
1595-3626
(11.0 -25.0)
NA = not available
10
Beeldens 2001
Kajio et al. 1998
Wang et al, submitted to NRMCA Concrete Technology Forum: Focus on Pervious Concrete, May 24-25, 2006, Nashville, TN
Based on the results from available literature and the present study, the performance-based mix
design criteria for PCPC in a cold weather climate are proposed as follows:
(1) water permeability: ≥ 140 in./hour (0.1 cm/sec )
(2) compressive strength at 28 days: ≥ 3000 psi (20 MPa )
(3) F-T durability (based on ASTM C666-Procedure A): ≤5% after 300 F-T cycles.
These preliminary mix design criteria should be verified in field, and other important durability
issues, such as clogging and wearing resistance, may be considered in the mix design in future.
In order to meet the above permeability criterion, larger than 140 in/hour (0.1 cm/sec ), selecting
coarse aggregate with proper void content is very important. Based on the present study, the void
content of raw coarse aggregate should be higher than 35%. In the present study, a raw coarse
aggregate, #4RG, had void content of 38.5%. The void content of the PCPC made with this
aggregate was 25.3%, decreased approximate 10% when compared with raw aggregate. After
replacing 7% of the coarse aggregate with sand (for strength and durability improvement), the
corresponding PCPC had another deduction in the void content by 10%. As a result, the PCPC
mix (Mix 2A: #4 RG with 7% sand) had void content of 18.5% and permeability of 140 in./hour
(0.1 cm/sec ). This sequential deduction of void content may provide engineers with an insight to
aid selection of raw aggregate materials in PCPC mix design.
There are many factors affecting concrete strength, such as concrete materials, w/c, mixing and
consolidation methods, some of which (such as consolidation) are discussed by authors in a
separate paper. To meet the PCPC strength criterion above, using small amount of sand (7%
weight of total aggregate in the present study) is recommended for the concrete permeability and
cost considerations. The recommend w/c is 0.27 or lower; however, it can be further reduced if
workability of the concrete is improved. The cement content should be just enough to coat the
aggregate particles with a thin layer. In the present study, cement content of 570 lb/cy (338
kg/m3 ) was used for most mixes. The calculated average paste thickness around aggregate
particles in these PCPC mixes is approximate 0.008” (200 micrometer). Excessive cement may
seal the voids between aggregate particles and significant reduces permeability of the concrete.
However, cement content may vary when different aggregate is used.
For conventional concrete, F-T resistance of concrete largely depends on aggregate quality,
concrete air void system (especially the void spacing factor) and strength (especially the strength
of the interfacial transition zone between aggregate and cement paste). It is well accepted that
concrete with void spacing factor of 0.008” (200 micrometer) generally has good F-T resistance.
In PCPC, void system may be less important due to the open structure of the material. As
mentioned above, the calculated average paste thickness around aggregate particles in the most
PCPC mixes studied is approximate 0.008” (200 micrometer), which indicates that requirement
for AEA might be arbitrary. However, it was observed under microscope that the paste thickness
in some regions of the PCPC was often larger than the average value. Therefore, AEA is still
recommended for the PCPC application under a cold weather condition until further research is
conducted.
Figure 7 has shown that PCPC F-T durability increases with concrete strength, especially the
splitting tensile strength. Addition of micro-fiber or latex generally increases concrete tensile
strength, and it therefore is recommended for the PCPC in the cold weather climate region. (Note
that some latex modified PCPC in the present study did not perform well during the F-T tests,
11
Wang et al, submitted to NRMCA Concrete Technology Forum: Focus on Pervious Concrete, May 24-25, 2006, Nashville, TN
which is probably because the latex was used for cement replacement, rather than addition.)
Based on the present study, the recommend 28-day splitting tensile strength value for the PCPC
in the cold weather climate region is 360 psi (2.5 MPa) and higher.
Concluding Remarks
In the present paper, effects of concrete materials (coarse aggregate, sand, cementitious
materials, fibers, and latex) and mix proportions on PCPC functional properties (permeability
and strength), quality control properties (void content and unit weight), and F-T durability are
evaluated. The relationships between these properties are explored. The PCPC mix design
criteria and considerations are discussed. The study concludes that when properly designed and
constructed, PCPC can have an excellent serviceability under cold weather conditions. Proper
strength and F-T durability of PCPC can be achieved by use small amount of sand and microfibers in the concrete.
References
Beeldens, A,. Van Gemert, D., and Caestecker, C. (2003). Porous Concrete: Laboratory Versus Field
Experience. Proceedings 9th International Symposium on Concrete Roads, Istanbul, Turkey.
Kajio, S., Tanaka, S., Tomita, R., Noda, E., and Hashimoto, S. (1998). Properties of Porous Concrete with
High Strength, Proceedings 8th International Symposium on Concrete Roads, Lisbon, pp 171177.
National Ready Mixed Concrete Association (NRMCA). (2004). Freeze-Thaw Resistance of Pervious
Concrete.
Olek, J., and Weiss, W. J., (2003). Development of Quiet and Durable Porous Portland Cement Concrete
Paving Materials. Final Report SQDH 2003-5 Center for Advanced Cement Based Materials,
Purdue.
Park, S., and M. Tia. (2004). An experimental study on the water-purification properties of porous
concrete. Cement and Concrete Research 34,177-184
Ramakrishnan, V. (1992) “Latex-Modified Concrete and Mortars,” NCHRP Synthesis 179,
Transportation Research Board, National Research Council, Washington, D.C.
Tamai, M., and Yoshida, M. (2003). “Durability of Porous Concrete.” Paper presented at the Sixth
International Conference on Durability of Concrete, American Concrete Institute.
Tennis, P.D., Leming, M.L., and Akers, D.J. (2004). Pervious Concrete Pavements, Special Publication
by the Portland Cement Association and the National Ready Mixed Concrete Association.
United States Department of Agriculture (USDA). (1986). Technical Release 55: Urban
Hydrology for Small Watersheds.
Youngs, Andy. (2005). Pervious Concrete It’s for Real. Presentation at Pervious Concrete and Parking
Area Design Workshop, Omaha.
12