USE OF PERVIOUS CONCRETE FOR STORM WATER MANAGEMENT

Transcription

1 USE OF PERVIOUS CONCRETE FOR STORM WATER MANAGEMENT Aniket Ambare 1 and Pravin S. Chaudhari 2 1 PG.Student, Civil and Environmental Engineering Department, V.J.T.I. Mumbai , Maharashtra India 2 Assistant Professor, Civil and Environmental Engineering Department, V.J.T.I. Mumbai , Maharashtra India Abstract- The groundwater reserves have been depleting day by day since the late 20 th century due to increase in pumping of water from the ground, at a faster rate than replanting construction of asphalt and cement concrete road due to which percolation of water is preventing to this problem pervious concrete presents a promising solution. Pervious concrete when used in places where there is light moving loads or dead load like footpath, sidewalk, 2 wheeler parking lots etc. can facilitate in replenishing the ground water and reducing storm water runoff. Pervious concrete in its original from has higher voids contents and porosity due to which infiltration rate of water through the concrete increases, but this consequently decreases the strength of the concrete. In this project an attempt was made to increase the strength of pervious concrete by maintaining all the useful properties, by the addition of polypropylene fibers to the pervious concrete. A mix design was prepared for both pervious concrete with fiber and without fiber by using ACI 522R. Pervious concrete trial mixes were prepared and tested for compressive strength & workability and comparison between both the samples was made. The pervious concrete mix was checked for void content, porosity and infiltration rate was also tested. Keywords- Pervious concrete, compressive strength, workability, infiltration rate. I. INTRODUCTION Pervious concrete is similar to conventional concrete except that it has an intentionally created network of interconnected voids that allow water to pass through the concrete matrix. These voids are typically 15-35% of the total volume of the concrete. [1] The voids are maintained through placement and compaction by using gap graded coarse aggregate and a viscous cement paste that prevents the separation of paste and aggregates. Additionally, fine aggregate is typically omitted from pervious concrete because it increases the paste volume and decreases the interconnected void volume. [1] Pervious concrete is used in parking areas, areas with light traffic, residential streets, pedestrian walkways, and greenhouses. It is an important application for sustainable construction and is one of the techniques used for ground water recharge. [4] Pervious concrete pavement in rural areas is a unique and effective means to achieve important environmental issues and support green, sustainable growth.[4] By capturing storm water and allowing it to seep into the ground, porous concrete is instrumental in recharging groundwater, reducing storm water runoff. A. Need of study In areas large amount of rainwater ends up falling on impervious surfaces such as parking lots, driveways, sidewalks, and streets rather than soaking into the soil. This creates an imbalance in the natural ecosystem and leads to a host of problems including erosion, floods, ground water level depletion and pollution of rivers, as rainwater rushing across pavement surfaces picks up everything from oil and grease spills to de-icing salts and chemical fertilizers. A simple solution to avoid these problems is to stop constructing impervious surfaces that block natural water infiltration into the soil. Rather than building them with conventional concrete, we should be switching to Pervious Concrete or Porous Pavement, a material that offers the inherent DOI: /IJMTER MFPW 179

2 durability and low life-cycle costs of a typical concrete pavement while retaining storm water runoff and replenishing local watershed systems. Instead of preventing infiltration of water into the soil, pervious pavement assists the process by capturing rainwater in a network of voids and allowing it to percolate into the underlying soil. II. OBJECTIVES OF THE STUDY The objectives of the current study as follows, a) To increase the strength of the pervious road by using suitable strengthen materials. b) To minimize the cost per unit cubic meter of pervious concrete in comparison to impervious concrete. III. METHODOLOGY From literature survey provides technical information on pervious concrete applications, design method, materials properties, mixture proportioning, construction methods, testing and inspections. The term Pervious concrete typically describe a near zero slump, open graded material consisting of cement, coarse aggregate, admixture, water and fiber. The combination of this ingredient will produce a hardened material with connected pores range in size from 2 to 8mm that allows to pass through easily. The void content can range from 15 to 35% with typical compressive strength of 3 to 28 MPa.[3] The drainage rate of pervious concrete will vary with aggregate size and density of the mixture, but will generally fall into range of 81 to 730 l/min/m 3.[3] A. Methodology Flow chart The methodology adopted carried out is presented in the form of flow chart After identification of problem and setting the objectives of the research, the research methodology has carefully design to achieve above mentioned objectives also the sequential activities involved in this study are presented in flow chart as shown in figure 1. Figure 1. Flow Chart of Methodology used for experimental All rights Reserved 180

3 B. Identification of problem India is facing a typical problem of ground water table falling at a fast rate due to reduced recharge of rainwater into subsoil and unplanned water withdrawal for agriculture and industry by pumping. Pervious Concrete is adopted for construction of pavements, platform/walkways, parking lots designed for lighter load, can help in improving recharging of rainwater. It can become a component of rainwater harvesting schemes being prepared by Government of India on a Priority basis C. Material Procurement for Experiment 1. Cement: OPC 53 grade is used as per IS (1987) with specific gravity The percentage of water required for standard consistency is 31.5 %. The initial and final setting times of cement were 60 min and 270 min. 2. Aggregate: Aggregate used in pervious concrete are typically single sized aggregate 10mm. Rounded and crushed aggregates have been used to make pervious concrete. The specific gravity of coarse aggregate is Water: Water-to-cement ratios between 0.27 and 0.40 are used routinely with proper inclusion of chemical admixtures, and those as high as 0.35 have been used successfully. The relation between strength and water-to-cement ratio is not clear for pervious concrete, because unlike conventional concrete, the total paste content is less than the voids content between the aggregates. 4. Admixture: The Mid Polyvinyl Chloride is used in concrete the density is 1.1 kg/m 3 5. Fibre: Polypropylene Fibers 12 mm Polypropylene fibers were introduced into the paste to enhance the post-cracking behavior of the paste. To ensure proper dispersion of these fibers, they were initially separated using an air compressor prior to mixing. The fiber was used at 2% by volume of concrete.[2] D. Concrete Mix Design The advance concrete mix design was used for designing the mix which uses ACI 522R-10 guidelines Pervious concrete. The various steps involved in the mix design are given below: Step 1: Determine aggregate Weight Percentage fine Aggregate Table 1 Effective b/b0 values (ACI 522R-10) b/bo ASTM C33/C33M Size no/. 8 ASTM C33/C33M Size no/ Density of 10 mm aggregate = 1600 kg/m 3 W a = 0.99 x 1600 = 1584 kg/ m 3 Step 2: Adjust to SSD weight W SSD = 1584 x 1.2 W SSD = kg/m 3 Step 3: Determine paste volume Void percent = 10% Cement Paste = 32% V p = 0.32 x 27 = 8.64 ft 3 = m All rights Reserved 181

4 Step 4: Determine Cement Content [ ( ) ] [ ( ) ] c = Kg/m 3 Step 5: Determine Water Content: ( ) w = 368 x 0.35 = Kg/m 3 Step 6: Determine Solid Volume Aggregate Volume V a = / (2.74 x 1000) = 0.65 m 3 Volume of cement V c = 368 / (3.15 x1000) = 0.11 m 3 Water volume V w = 129 / 1000 = m 3 Total solids volume V s = = m 3 Figure 2. Relation between paste and void content (ACI 522R -10) Step 7: Check percent voids ( ) = = [( )/1)] x100 = = 11.1 % Step 8: Iterative trial batching and testing The trial batch weight per cubic meter are as follows: Table 2. Quantity of material required per meter cube of concrete in kg Material Quantity per m 3 Cement Aggregate Water Admixture 2 % Total weight Density of concrete 368 Kg 1900 kg 129 Kg 7.3 kg kg kg E. Casting and Curing The moulds of 150x150x150 mm were well cleaned and the internal faces were completely oiled to avoid adhesion with the concrete after hardening. The casting was carried out in one layer without compaction. The specimens were demoulded after 24 hours. After demoulding, the specimens were completely immersed in All rights Reserved 182

5 Figure 3. Casting cube F. Testing The field trials were carried out in fully equipped laboratory in controlled environment. For each trial mix, slump cone test was measured workability of concrete. For each trial mix, 9 cubes and in total 21 cubes of size 15x15x15 cm was casted for different tests. 3 cubes each were tested for 7 days, 14 days, 28 days compressive strength. The different tests carried out are as follows, [3] 1. Slump cone test 2.Compressive strength 3.Void content 4.Porosity IV. RESULT AND DISCUSSION The study was conducted to make a clear comparison between compressive strength of pervious concrete with and without addition of fibers is carried out, The other parameters of pervious concrete like Infiltration Rate, Void ratio, Porosity is determined. The experimental results are discussed as below. A. Workability The test for workability was conducted by using slump cone method by taking two trial mixes and the following table 3 shows the results obtained, Table 3. Result of Slump Cone Test Sr.No Mix Proportion Workability (Slump in mm) Admixture Dosage (%) Cement Aggregate Water Fibre (%) Form the workability test it can be seen that with the addition of 2% fibers to the pervious concrete, there is significant improvement workability of concrete in comparison to pervious concrete without fiber. B. Compressive Strength The test for determining the compressive strength of pervious concrete with fiber and without addition of fibers are conducted by using mix design as discussed above. The compressive strength for pervious concrete with fiber and without addition of fiber were conducted for interval of 7 days, 14 days and 28 days the results obtained are summarized as All rights Reserved 183

6 Compressive Strenght International Journal of Modern Trends in Engineering and Research (IJMTER) Compressive Strength No of Days Adding Fibre in PC Pervious Concrete (PC) Figure 4. Comparison of compressive strength of Pervious concrete From the above (figure 4) graph a clear difference between the compressive strength of pervious concrete with fibers and without fibers is observed. With the addition of fibers to the pervious concrete there is increase the compressive strength of concrete for 7days, 14 days & 28 days. An average increased in compressive strength by 12.95% is seen with the addition of fibers to the pervious concrete. C. Void Content The void ratio for the pervious concrete without fibers was calculated by using ASTM c1688/1688m [5] for fresh concrete following calculation & results are as follows: 1.Unit Weight: 2.Theoretical Density 3.Void Content % The void content considered for the mix design was 10%, the calculated void content for the mix design came out to be 11.80%. This void content will increase the permeability of water over the pervious concrete pavement and help in the drainage of water to the sub catchment. D. Porosity The total porosity was measured by finding the difference of the pervious concrete. ( ( ) ) Where, is the total porosity of the pervious concrete (%), is the pervious concrete sample weight air-dried for 24 h (kg), is the pervious concrete sample submerged underwater weight (kg), is the pervious concrete sample volume (mm3 ), is density of water (kg/mm3 All rights Reserved 184

7 ( ( ) ) The porosity was obtained by taking into consideration the air dried cube, the higher is porosity the better will be permeability and more water will be drain from the pervious concrete pavement.d 2 E. Infiltration Rate The infiltration rate (I) is calculated as follows: Where, I is Infiltration rate, mm/h, M is Mass of infiltrated water, kg, D is Inside diameter of infiltration ring mm, t is time required for measured amount of water to infiltrate the concrete K= in SI units V. CONCLUSION As a result of this study, the following conclusions can be drawn: The workability of pervious concrete with & without fiber was conducted by slump cone test by the comparing the results for the both type of samples the workability for sample with fiber was observed to be more than sample without fibers. Both the samples were tested for compressive strength at an interval of 7 days, 14 days & 28 days the samples with fibers had an average increase in compressive strength by factor of 12.95% compare to that without fibers. This shows that addition of fibers pervious concrete improve the strength of pervious concrete. This pervious concrete can be used for parking lots, foot path etc. and will be able to resists the loads of the vehicles and pedestrian for a longer duration while draining the surface water at the same time. The void ratio for the fresh pervious concrete was calculated and found out to 11.80% this void ratio is sufficient for draining pavement water to the sub catchment area. Due to more voids in pervious concrete it is difficult to high strength. Porosity for pervious concrete was calculated in harden concrete state, the more porous is the concrete more will be the permeability and faster will be percolation rate of the water. The infiltration was found at to be mm/hr which is within the range for effective permeability for the pervious concrete. Higher the infiltration rate faster will be the drainage of water through the pavement. REFERENCES [1] Mary E. V., Kevin M, & Lev K. (2012), Location and Depth of Pervious Concrete Clogging Material before and after Void Maintenance with Common Municipal Utility Vehicles, American Society of Civil Engineers, Vol. 138, [2] Amanda L. A., Mahsa H. D.,Anto S.,& Dr. Medhat S.(2010), Optimizing the strength and permeability of pervious concrete, Permeable Pavement Design And Technology All rights Reserved 185

8 [3] Jing Y & Guoliang J, (2002), Experimental study on properties of pervious concrete pavement materials, Elsevier Science, [4] Anush K. C,& Krishna P. B.(2016), Pervious concrete as a sustainable pavement material Research findings and future prospects: A state-of-the-art review, Elsevier Science,Vol 111, [5] ACI 522R -10 Report on Pervious Concrete [6] ASTM C 1688 Standard Test Method for Density and Void Content of Freshly Mixed Pervious Concrete [7] ASTM 1701 Standard Test Method for Infiltration Rate of In Place Pervious Concrete [1] All rights Reserved 186