STUDY ON AXIAL STRESS-STRAIN RELATION AND POISSON S RATIO EFFECT ON COCONUT SHELL CONCRETE

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1 International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 4, April 2018, pp , Article ID: IJCIET_09_04_040 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed STUDY ON AXIAL STRESS-STRAIN RELATION AND POISSON S RATIO EFFECT ON COCONUT SHELL CONCRETE Pramod Kumar M. V M. Tech Structural Engineering, School of Civil Engineering and Chemical Engineering, Vellore Institute of Technology, Vellore, Tamil Nadu Visuvasam J, Srinivasan. K, Simon Jayasingh Assistant Professor, School of Civil and Chemical Engineering, Vellore Institute of Technology, Vellore, Tamil Nadu ABSTRACT The paper deals with the experimental investigation on the determination of axial stress-strain relation, the concrete thoroughly made with the lightweight aggregate of coconut shell. Four different grades of coconut shell concrete were used in the experiment. The coefficient of secant modulus and modulus of elasticity and chord modulus variations were observed. The experiment is entirely done with extensometer, stress-strain relations were observed. The empirical equations were finally proposed to describe the stress-strain relation of coconut shell concrete. Key words: Coconut Shell Concrete, Axial Stress-Stress Relation, Strain Gauges. Cite this Article: Pramod Kumar M. V, Visuvasam J, Srinivasan. K and Simon Jayasingh, Study On Axial Stress-Strain Relation and Poisson s Ratio Effect On Coconut Shell Concrete, International Journal of Civil Engineering and Technology, 9(4), 2018, pp INTRODUCTION 1.1. General Coconut shell concrete (CSC) is one of the unique concrete under lightweight concrete which is recently developed in the concrete world. The mechanical properties and bond properties of CSC [1] and durable properties of CSC [2] and torsional behavior of CSC [3] and excellent flexural and ductility behavior [4] are in acceptable range and similar to the lightweight concrete. Compressive strength, porosity in the concrete, water-to-cement ratio and curing temperature affect the development of stress-strain relation of concrete [5] and also an internal matrix of aggregate hugely impact on the stress-strain behavior and Poisson's ratio. In the experimental program, we made an attempt that we have developed four mix proportions of editor@iaeme.com

2 Pramod Kumar M. V, Visuvasam J, Srinivasan. K and Simon Jayasingh CSC we have tested, we found in the results there is a significant effect of aggregate type on the modulus of elasticity and Poisson's ratio. 2. MATERIALS USED IN THE STUDY 2.1. Cement Ordinary Portland cement is one of the finest, in this project OPC, 53 grade has been taken according to IS [6]. The initial setting time to be 30 minutes and final setting time to be 10 hours and having a specific gravity of Fine Aggregate River sand is used as a fine aggregate which is cheaply available in the coastal belt of Andhra Pradesh has been sieved through 4.75 mm come under zone 3 according to IS [7]. The sand is free from biodegradable matter; the fineness modulus and specific gravity are 2.61 and 2.72 respectively Water Regular water has a PH of 7 has been used in the project for mixing the ingredients and casting as well as curing according to IS [8] Coconut Shell Coconut shells were collected from near oil crushers in this project coconut shells used as a coarse aggregate, which is passed from 12.5 mm sieve and retains on 10 mm sieve. The specific gravity and water absorption capacities are 1.13 and 23.4 % Mix Design For the manufacture of CSC, it mainly depends upon the physical properties of the shell. The chosen mix proportions of M15, M20, M25, M30 as represented as Mix Ids M1, M2, M3, M4 which are the best fit for the stress-strain curve. Gunasekaran et al. [2] have developed a Mix proportion of 1:1.47:0.65:0.42 having cement content of 510 kg/m 3 with this reference we have calculated the mix proportions for M15 and M20 and M EXPERIMENTAL METHODS 3.1. Compressive Strength test The compressive strength of concrete, a high priority component in the structural design, is entirely considered as one of the most important mechanical properties which notify the quality of the concrete. The cubes of size 100 mm x 100 mm x 100 mm were tested (Figure 1) in digital compression testing machine having a maximum capacity of 20 Tons to determine compressive strength as per IS 516:1959 [9] editor@iaeme.com

3 Study On Axial Stress-Strain Relation and Poisson s Ratio Effect On Coconut Shell Concrete (a) Testing of specimen (b) Tested specimen Figure 1 Compressive strength test on CSC 3.2. Static Modulus of Elasticity and Poisson s Ratio Cylinders of 150mm diameter and 300mm height were taken to find the chord modulus of elasticity and Poisson's ratio of CSC. The test was carried out by using extensometer. The specimens were loaded up to 40% of the ultimate load as per ASTMC [10]. 4. DISCUSSION ON TEST RESULTS 4.1. Compressive Strength After curing of 3, 7 and 28 days, the cubical moulds of CSC are tested by using compression testing machine having a maximum capacity of 20 Tons. The average compressive strength of cubes was taken according to as per IS 516:1959. The compressive strength results of cylindrical and cubical specimens for 28 days have been tabulated below. Mix Id Cylinder Compressive Strength (MPa) Table 1 Testing results of hardened concrete of CSC Cube Compressive Strength (MPa) Unit Weight of Hardened Concrete (kg/m 3 ) M M M M From the above results, The CSC unit weight varies from 1900 kg/m 3 to 2000 kg/m 3 which meet the demand of lightweight structural concrete Axial Stress-Strain Behavior The total four different grades of CSC cubes were cast. The total cylinders were tested using extensometer. The unfold diagram of strain gauges has been represented below. Each cylindrical specimen has been attached to four strain gauges (Figure 2) editor@iaeme.com

4 Pramod Kumar M. V, Visuvasam J, Srinivasan. K and Simon Jayasingh (a) Unfolded diagram of strain gauges (b) Specimen with strain gauges Figure 2 Strain gauge arrangement Accordingly, both oblique strains and longitudinal strains have been measured, after measuring the strains using regression analysis the stress versus strain graphs were plotted for selected mix proportions. The stress-strain relationship of M3 mix obtained by extensometer is given in Figure 3. Figure 3 Stress vs strain of M3 mix by extensometer Secant modulus is the line from which origin to any point of the stress-strain curve. The secant modulus of the M3 mix by extensometer is given in Figure 4. Figure 4 Secant modulus of the M3 mix by an extensometer editor@iaeme.com

5 Study On Axial Stress-Strain Relation and Poisson s Ratio Effect On Coconut Shell Concrete From the above graphs, stress-strain characteristics of CSC are not similar to conventional concrete. Due to the higher elongation readings in CSC, the curves represent to be little zigzag. The obtained strain value is more at failure leads to the lower modulus of elasticity compared to conventional concrete as per IS 456:2000. The deformations and average modulus of elasticity of CSC are tabulated below Table 2. Table 2 Strain values of various mix proportions for 40% of ultimate load and peak stress. Mix Id Cylinder Compressive Strength (MPa) Strain at 40% of Ultimate Load Strain at Peak Stress M M M M The maximum strain achieved in the CSC is almost within the range of 0.002, the average modulus of elasticity M3 mix is MPa which is almost less than half of conventional concrete. Based on the test results the modulus of elasticity of CSC is compared with 5000 fck whereas fck is characteristic cube compressive strength. The stress strain relationship plot for the all mix proportions with obtained equation and regression factor values in the range of 0.95 to 0.99 is given in Figure 6. Figure 6 Stress vs strain curves for all selected mix ID 4.3. Comparison of Ec Results Table 3 Investigated and proposed modulus of elasticity results of all mix proportions Mix Id Maximum Strain Investigated Static Modulus(Mpa) Proposed Modulus 1580 Fck M M M M editor@iaeme.com

6 Pramod Kumar M. V, Visuvasam J, Srinivasan. K and Simon Jayasingh 4.4. Chord modulus and Poisson's ratio Chord modulus and Poisson s ratio has been calculated by using formula taken from ASTM469 [10] for the selected mix ids the values of chord modulus, modulus of elasticity is given below a table 4 Mix Id Modulus Of Elasticity(Mpa) Table 4 Secant Modulus (Mpa) Chord Modulus (Mpa) Poissons Ratio, µ M M M M From the above table it has been observed that the secant modulus of CSC within the range of 1550MPa to 1700MPa, and also modulus of elasticity has been recorded up to in the range of 1450MPa to 1600MPa which is decidedly less than when compared to conventional concrete. and also observed than Poisson's ratio within the range of( ) which meets the demand of structural lightweight concrete, but there observed a high deformations occurred in the lateral direction which leads more significant loss in weaker face of CSC. 5. CONCLUSIONS From this research, the stress-strain characteristics of CSC are studied, the following conclusions are obtained. Compressive strength and the elastic modulus of CSC are significantly influenced by the mineralogy of coconut shell. The experiments of coconut shell achieve the requirements for use as lightweight aggregate concrete. CSC being a lightweight has the more significant difference in properties such as compressive strength, density, ultimate strain, elastic modulus, Poisson's ratio. The compressive strength of cylinder to cube ratio is achieved as 0.65, which is decreased by 18% compared to conventional concrete. For coconut shell, the maximum strain obtained was as similar as conventional concrete The modulus of elasticity of CSC varies from 1400MPa to 1600MPa The chord modulus for CSC varies from 7.5GPa to 9GPa is very much lower than conventional as per IS456:2000 Based on stress vs strain the final coefficient obtained for different grades of concrete as per IS456 E c=1510 f ck The Poisson's ratio of CSC results in the range of which is meeting the demand of lightweight concrete. The lateral strains of CSC are more due to its weaker interface, which increases Poisson's ratio editor@iaeme.com

7 Study On Axial Stress-Strain Relation and Poisson s Ratio Effect On Coconut Shell Concrete REFERENCES [1] Gunasekaran, K., P. S. Kumar, and M. Lakshmipathy. "Mechanical and bond properties of coconut shell concrete." Construction and building materials 25.1 (2011): [2] Gunasekaran, K., R. Annadurai, and P. S. Kumar. "A study on some durability properties of coconut shell aggregate concrete." Materials and Structures 48.5 (2015): [3] Gunasekaran, K., R. Ramasubramani, R. Annadurai, and S. Prakash Chandra. "Study on reinforced lightweight coconut shell concrete beam behaviour under torsion." Materials & Design 57 (2014): [4] Gunasekaran, K., R. Annadurai, and P. S. Kumar. "Study on reinforced lightweight coconut shell concrete beam behaviour under flexure." Materials & Design 46 (2013): [5] [6] Zhou, Yong, et al. "A fundamental study on compressive strength, static and dynamic elastic moduli of young concrete." Construction and Building Materials 98 (2015): [7] [8] The designation, Indian Standard. "IS , Specification for 53 grade ordinary Portland cement, Bureau of Indian Standards, New Delhi, India." Indian Standard Designation, IS [9] Bureau of Indian Standard (BIS), Specification for Coarse and Fine Aggregate From Natural Sources for Concrete, IS 383(Second rev.), p. New Delhi, India,1970. [10] IS Plain and Reinforced Concrete - Code of Practice is an Indian Standard code of practice for general structural use of plain and reinforced concrete [11] Bureau of Indian Standards, IS : Method of Tests for Strength of Concrete, Is Methods of Tests for Strength of Concrete, [12] R. Udhayasankar and B. Karthikeyan, Mechanical, Thermal, and Morphological Properties of Coconut Shell Biocomposites Reinforced with Cardanol Resin, International Journal of Mechanical Engineering and Technology 8(11), 2017, pp [13] H. Ajith Hebbar, Anvith A Hebbar and Dayananda Patwardhan. Novel and Eco Friendly Ant Chalk and Mosquito Mat From Coconut Shell Oil. International Journal of Advanced Research in Engineering and Technology, 6(10), 2015, pp [14] Dewanshu Ahlawat and, L.G.Kalurkar, Strength Properties of Coconut Shell Concrete, Volume 4, Issue 7, November-December 2013, pp , International Journal of Advanced Research in Engineering and Technology (IJARET) [15] Vikesh B.S and K. Gunasekaran, Study for the Development of Stress Block for Coconut Shell Concrete. International Journal of Civil Engineering and Technology, 8(4), 2017, pp [16] ASTM C , Standard Test Method for Static Modulus of Elasticity and Poisson s Ratio of Concrete in Compression, Annual Book of ASTM standards editor@iaeme.com