18_ by ides editor

Full Paper Proc. of Int. Conf. on Advances in Civil Engineering 2012

Mechanical Properties of Pervious Concrete Sanket Sharma1,Sarita Singla2 and Taranjeet Kaur3 1

PEC University of Technology, Chandigarh, India Email: sanket414@gmail.com 2 PEC University of Technology, Chandigarh, India Email: {ssaritasingla@yahoo.com, taran_madan@yahoo.co.in} Abstract—The term pervious concrete typically describes a near-zero-slump, open-graded material consisting of portland cement, coarse aggregate, little or no fine aggregate, admixtures, and water. The combination of these ingredients will produce a hardened material with connected pores, ranging in size from 0.08 to 0.32 in. (2 to 8 mm), that allow water to pass through easily. The objective was to investigate the effects of percentage of fine aggregates and cement to coarse aggregate ratio on the important engineering properties of pervious concrete. As per the test results, maximum compressive strength of pervious concrete was achieved by using the 20mm graded aggregate and 1:4 cement: total aggregate ratio. The maximum cube compressive strength achieved at 7 days was 17.91 N/mm2 and 27.1 N/mm2 at 28 days. Maximum water permeability of order 3.39 X10 -4 cm/ sec was achieved which is about 3.4 times more permeable than high permeability concrete. Index Terms — Pervious Concrete, no fines concrete, cube compressive strength, cylinder compressive strength, split tensile strength, flexural strength and permeability.

Fig. 1. Pervious Concrete

A. Historical Background The use of no-fines concrete as a pavement material had been extremely limited and had only recently been developed for this particular application. However, no-fines concrete had been used extensively as a structural building material in Europe, Australia and the Middle East for over 70 years (Macintosh et al. 1965)[2]. The use of no-fines concrete became considerably more widespread during the material shortages after World War II, for cast-in place load bearing walls of single and multi-storey buildings. In recent years no-fines concrete had been used as a load bearing material in high rise buildings up to ten-storey. The most remarkable use of this form of concrete was undertaken in Stuttgart, Germany where a high rise building was constructed using conventional concrete for the six bottom storey and no-fines for the remaining thirteen upper storeys (Malhotra 1976)[3]. Offenberg stated that the first popular usage of pervious concrete was in post-World War II England where it was used in two-story homes known as the Wimpey Houses [4]. No-fine concrete was then used in some parts of the walls by Wimpey architects and engineers to decrease the cost. Some of the applications for pervious concrete involved residential roads, driveway, sidewalks, parking lots, low water crossings, artificial reefs, slope stabilization, noise barriers, tennis court, swimming pool decks, and zoo areas.

I. INTRODUCTION Pervious concrete was a special high porous concrete used for flatwork applications that allow water from precipitation and other sources to pass through, thereby reducing the runoff from a site and Recharging ground water levels. Its void content ranged from 18 to 35 % with compressive strengths of 400 to 4000 psi (28 to 281 kg/cm2)[1]. Typically, pervious concrete had little or no fine aggregate and had just enough cementitious paste to coat the coarse aggregate particles while preserving the interconnectivity of the voids. Taking advantage of the corresponding decreased density, the concrete was incredibly permeable while still able to provide a quality structural pavement. Instead of moisture (e.g. rain/snow melt) running off the surface horizontally, virtually all storm water falling onto pervious concrete immediately drained directly down through the pavement to the sub grade, eliminating runoff while providing filtration and ground water recharge. Pervious concrete resembled an open-cell material with an appearance sometimes described as that of a “Rice Krispies” treat. Nevertheless, the product could be integrally colored, painted, or otherwise modified to be aesthetically in tune with the project environment in the same ways as conventional concrete. It could even be made acceptably smooth for good shopping cart mobility by the means of rapidly advancing placing techniques, equipment, and concrete mix design technology while still maintaining a non -slip surface. © 2012 ACEE DOI: 02.AETACE.2012.3.18

B. Benefits and Problems of Pervious Concrete Mix One of the primary uses of pervious concrete is in storm water management. Due to its high porosity, pervious concrete 161

Full Paper Proc. of Int. Conf. on Advances in Civil Engineering 2012 can capture storm water and provide a pathfor water to flow into the subsoil, helping to naturally adjust the ground water level. Secondly, pervious concrete is much cooler than asphalt and conventional concrete. The light color reflects more ultraviolet rays from sun and absorbs less heat than asphalt. Pervious concrete shows several advantages on traffic. The large amounts of voids in pervious concrete are beneficial to reducing traffic noise. Pervious concrete enhances the safety of driving during raining because of the elimination of ponding. High porosity is the necessary condition that makes pervious concrete permeable, and is the main beneficial characteristic of pervious concrete. However it can cause problems that limit the utilization of pervious concrete. The bearing capacity of pervious concrete is decreased because of the existence of large amounts of air voids. The low strength limits the utilization of pervious concrete to parkinglots, sidewalks, and other low-volume traffic roadways. Abrasion of pervious concrete may limit its utilization. Raveling may happen if aggregate is not sufficiently coated with cement paste. Clogging is an unavoidable problem due to the existence of voids in pervious concrete. The open voids are highly prone to be clogged during the utilization of pervious concrete pavement over time. Typically, the initial cost of pervious concrete is greater than that of conventional concrete. However, because the lifespan of pervious concrete is longer than that of the regular concrete, some of the added cost is offset. The high initial cost of pervious concrete is partly caused by the construction of the sub grade.

used for all concrete mixes. The fine aggregates were obtained from ghaggar river and were first sieved through 4.75 mm sieve to remove any particles greater than 4.75 mm and it was found to be complying with Zone III. The specific gravity of fine aggregates was 2.60 and fineness modulus as 2.13. The coarse aggregate used were crushed 20mm graded aggregate with specific gravity of 2.6. Potable tap water was used for casting and curing of specimen. B. Final Mix Proportions Selected Based upon the trial mixes results, the cement content in the pervious concrete was fixed as 400Kg/m3. The water cement ratio was also fixed as 0.3. The corresponding mix proportions for the selected mixes of pervious concrete are shown in Table II. TABLE II. MIX PROPORTIONS OF D IFFERENT MIXES

C. Preparation of Test Specimens. The casting was carried out using a tilted drum type concrete mixer to ensure uniform mixing of ingredients. The specimens were cast in steel moulds and compacted on a table vibrator. Curing was done for 28 days by keeping the specimens completely immersed in potable water. The test results reported in this paper represents the average value obtained from a minimum of three specimens.

C. Recommended Design of Pervious Concrete Mix Pervious concrete mix design had generated batches that satisfy compressive strength and permeability requirements. Typical mix designs of pervious concrete had been recommended by different agencies such as National Ready Mixed Concrete Association (NRMCA), the Southern California Ready Mix Concrete Association (SCRMCA) and the Euclid Chemical Company (ECC) [5]. Refer Table I.

III. ANALYSIS OF TEST RESULTS The concrete specimens were tested after 7 days and 28 days of casting. The results of various test performed on the concrete mixes are discussed in the succeeding sections.

TABLE I. RECOMMENDED PERVIOUS CONCRETE MIX PROPORTIONS

A. Cube Compressive Strength Cube compressive strength of mixes at various ages is given in Table III. TABLE III. CUBE C OMPRESSIVE STRENGTH AT VARIOUS AGES

II. EXPERIMENTAL PROGRAM The test program was planned to investigate the mechanical behavior of pervious concrete. A. Physical Properties of Materials Used The constituent materials which were used for making pervious concrete were tested as per IS codal provisions and were found to be complying with the codal requirements. In the present investigation, ordinary portland cement of 43 grade from a single batch conforming to IS: 10262:2009 was ÂŠ 2012 ACEE DOI: 02.AETACE.2012.3.18

162

Full Paper Proc. of Int. Conf. on Advances in Civil Engineering 2012 Effect of Percentage of Fine Aggregate For 1:4 cement: total aggregate ratio mixes (C1,C2,C3) with no fines the cube compressive strength at 7 days was found to be 11.63 N/mm2, with 5 % fine aggregates the strength increased by about 5 %. With 10 % fine aggregates the cube compressive strength increased by about 50 %. The maximum cube compressive strength achieved at 28 days was 27.1 N/mm2 for C3 mix. For 1:5 cement: total aggregate ratio mixes (C4,C5,C6) with 5 % fine aggregates the cube compressive strength decreased by about 10 % - 15 %. Whereas with addition of 10 % fine aggregates the strength decreased by about 10 %. Effect of Cement: Total Aggregates Ratio For 1:4 ratio mixes gave the strength achieved was more than 1:5 ratio mixes. There was about 70 % increase in cube compressive strength at 7 days and about 45 % increase in strength at 28 days in 1:4 mixes as compared to 1:5 mixes.

TABLE V. SPLIT TENSILE STRENGTH AT VARIOUS AGES

Effect of Percentage of Fine Aggregate For 1:4 (cement: total aggregate ratio) mixes (C1,C2,C3) with no fines the cube compressive strength at 28 days was found to be 3.7 N/mm2 with 10 % fine aggregates the split tensile strength decreased by about 80 %. For 1:5 (cement: total aggregate ratio) mixes (C4, C5, C6) with 10 % fine aggregates the split tensile strength was increased by about 220 %. The maximum split tensile strength achieved at 7 days was 3.1 N/mm2 and at 28 days it was 4.5 N/mm2 for C6 mix. Effect of Cement: Total Aggregates Ratio Split tensile strength increased by changing ratio of (cement: total aggregate) 1:4 to 1:5. At 7 days there was about 43 % increase in split tensile strength when 1:5 mixes were used in place of 1:4 mixes and at 28 days there was about 46 % increase in split tensile strength by varying the cement: total aggregate ratio from 1:4 to 1:5 ratio.

B. Cylinder Compressive Strength Cylinder compressive strength of mixes at various ages is given in Table IV. TABLE IV. C YLINDER C OMPRESSIVE STRENGTH AT VARIOUS AGES

D. Flexural Strength Flexural strength of mixes at various ages is given in Table VI. TABLE VI. FLEXURAL STRENGTH AT VARIOUS AGES

Effect of Percentage of Fine Aggregate For 1:4 cement: total aggregate ratio (C1,C2,C3) with no fines the strength at 28 days was found to be 9.12 N/mm2, with 10 % fine aggregates the cylinder compressive strength variation was not significant. For 1:5 cement: total aggregate ratio mixes (C4,C5,C6) with 10 % fine aggregates the cylinder compressive strength decreased by about 50 %. The maximum cylinder compressive strength achieved at 7 days was 4.6 N/ mm2 and at 28 days it was 6.4 N/mm2 for C4 mix. Effect of Cement: Total Aggregates Ratio It was seen that strength increased by changing ratio of cement: total aggregates from 1:5 to 1:4. 1:4 ratio mixes gave more strength than 1:5 ratio mixes. With 0% fine aggregates there was about 30% increase in cylinder compressive strength at 7 days and about 40% increase at 28 days for 1:4 (cement: total aggregate) mixes as compared to 1:5 (cement: total aggregate) mixes.

Effect of Percentage of Fine Aggregate For 1:4 (cement: total aggregate) mixes (C1,C2,C3) with no fines concrete the strength was found to be 4.0 kg/cm2, with addition of 10 % fine aggregates the flexural strength increased by about 30 %. For 1:5 cement: total aggregate ratio mixes (C4,C5,C6) with addition of 10 % fine aggregates the flexural strength increased by about 50 % as compared to when no fine aggregates was added. The maximum flexural strength achieved at 7 days was 2.84 N/mm2 and at 28 days it was 3.83 N/mm2 for C6 mix. Effect of Cement: Total Aggregates Ratio In 1:4 (cement: total aggregate) mixes, there was 48% increase in strength at 7 days and about 31% increase in strength at 28 days as compared to 1:5(cement: total

C. Split Tensile Strength Split Tensile strength of mixes at various ages is given in Table V.

ÂŠ 2012 ACEE DOI: 02.AETACE.2012.3.18

163

Full Paper Proc. of Int. Conf. on Advances in Civil Engineering 2012 aggregate) mixes.

in percentage of fine aggregates. Compressive strength decreased with increase in cement: total aggregate ratio. Hence 1:4 mix proportions gave better strength as compared to 1:5 mix proportions. Split tensile strength for 1:5 cement: total aggregate mix increased by about 220% with addition of 10% fine aggregate when compared with mix having no fine aggregates. Flexural strength of pervious concrete increased by 50% with addition of 10% fine aggregates as compared to mix having no fine aggregates.

E. Permeability Water permeability test of pervious concrete was conducted according to IS: 3085 – 1965. Area (A) was kept constant as 225cm2. H/L ratio was also calculated as 112500. Fig 2 shows the water permeability of various mixes.

REFERENCES [1] American Concrete Institute (ACI). (2006) “Pervious Concrete, ACI 522 Committee Report, Farmington Hills, MI: ACI”. [2] Carolinas Ready Mixed Concrete Association, Inc. (2003) “Pervious Concrete Installation Course Information Packet”. Carolinas Ready Mixes Concrete Association Inc. Revised July 2003. [3] Kevern, J. T., (2006) “Mix Design Development for Portland Cement Pervious Concrete in Cold Weather Climates.” M.S. Thesis. Ames, IA: Iowa State University. [4] Malhotra, V. M. 1976. “No-Fines Concrete – Its Properties and Applications”. [5] Journal of the American Concrete Institute. Vol 73. No. 11. [6] Meininger, Richard C. 1988. “No-Fines Pervious Concrete for Paving Concrete”. [7] International: Design and Construction. Vol 10. No. 8. August. [8] Neville, A. M. 1996. “Properties of Concrete”. John Wiley & Sons. Inc. New York. USA. [9] Ghafoori, Nader & Dutta, Shivaji. 1995. “Building and NonPavement Applications of No-Fines Concrete”.

Fig. 2. Water Permeability of Pervious Concrete

CONCLUSIONS Compressive strength increased by addition of 5% fine aggregates but the strength decreased with further increase

164