STRENGTH AND DUCTILITY OF POLYMER MODIFIED STEEL FIBER REINFORCED FLEXURAL MEMBER

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1 International Journal of Advanced Research in Engineering and Technology (IJARET) Volume 7, Issue 3, May June 2016, pp , Article ID: IJARET_07_03_012 Available online at ISSN Print: and ISSN Online: IAEME Publication STRENGTH AND DUCTILITY OF POLYMER MODIFIED STEEL FIBER REINFORCED FLEXURAL MEMBER P. Palson Assistant Professor, Department of Civil and Structural Engineering, Annamalai University, Chidambaram K. Manimaran M.E. Student, Department of Civil and Structural Engineering, Annamalai University, Chidambaram ABSTRACT This study deals with the mechanical properties of conventional concrete, polymer modified concrete (SBR), and incorporation of steel fibres are studied with constant percentage of polymer (SBR) and various percentage of Steel fibre (0.5%, 1.0% and 1.5%). Based on the mechanical properties the mix proportion is optimized. This paper contains with flexural behaviour study of polymer modified concrete with and without steel fibres concrete beams. In this investigation the conventional concrete, constant percentage of polymer modified concrete and various percentages of Steel fibre (0.5%, 1.0% and 1.5%) specimens were cast for the slump range of 50 to 75 mm, and its mechanical behaviour was obtained from compression, E for concrete and Flexure test. The mix was finalized from Constant percentage of polymer and various percentage of Steel fibre. For the Finalized mix proportion from the mechanical properties, Two beams were cast for every Finalized mix (control + Polymer (10%), (control + Polymer (10%) + Steel Fibre) and the flexural behaviour were studied using static two point load and the results were compared with theoretical value. Keywords: Ductility, flexural strength, Styrene butadiene rubber- Latex, Steel fibres, etc. Cite this Article: P. Palson and K. Manimaran, Strength and Ductility of Polymer Modified Steel Fiber Reinforced Flexural Member, International Journal of Advanced Research in Engineering and Technology, 7(3), 2016, pp INTRODUCTION In order to improve the performance and durability of concrete, the allowance of polymer was introduced in the 1920s. Moreover, it provides a strong calcium silicate hydrate (CSH) aggregate bond, leading to increased tensile strength and fracture toughness. On the other editor@iaeme.com

2 Strength and Ductility of Polymer Modified Steel Fiber Reinforced Flexural Member hand, the sealing effect due to the polymer films also provides a considerable increase in waterproof or water tightness, resistance to moisture or air permeation, chemical resistance and freeze thaw durability. In civil engineers have been making good concrete with more improvement in its properties with development of super plasticizers and other admixture it is possible to achieve strength and durability of concrete. Further increase the strength addition of some material like, polymer solid content, etc. Hence improve the mechanical, physical and chemical properties of concrete and suitable polymer formations greatly improve the fundamental strength of concrete. The use of polymer modified concrete could be attributed to the increase the tensile strength of the polymer modified concrete compared to that of the conventional concrete. The type of curing for conventional concrete is Demoulded at 24hours form the time of casting, and The specimens were cured under pond curing for control concrete and for latex modified concrete 2 days wet curing by gunny bag, five days immersion curing and then air curing until the test date. Incorporation of Steel fiber in concrete is made to differently in different countries. Ductility can be defined as the ability of material to undergo large deformations without rupture before failure. In the case of reinforced concrete members subjected to inelastic deformation, not only strength but also ductility plays vital role in the design. A ductile material is the one that can undergo large strains while resisting loads. 2. PROPERTIES OF THE MATERILAS Fine Aggregate: Natural River sand passing through 4.75mm IS sieve having fineness modulus 3.12, specific gravity 2.61 and confirming to Zone III of IS 383:1970. Coarse aggregate: Crushed stone with a nominal maximum size of 20mm having fineness modulus 6.86 as per IS383:1970. Polymer Latex: Styrene Butadiene copolymer Latex manufactured by Fosroc India limited. Colour: Milky white emulsion ph: 8.5 Specific gravity 1.01 Total polymer solids: 50% Steel Fibre: Crimped Steel Fibre Used Diameter 0.6mm Length 30mm Aspect ratio 50 Materials addition and replacement: Latex 10% addition Crimped Steel Fiber 0.5%,1%,1.5% 2.1. Mix Design In this study concrete Mix M 30 was considered as control concrete (C).The mix design for the above grade of concrete as done based on IS10269:2009 for the workability range of 50-75mm. The control concrete mixture was comprised of Portland cement, water, coarse and fine aggregate. The mix proportion of control concrete is presented in Table 2. Polymer modified concrete (PMC): In this research Polymer modified concrete composition containing 10 %( CP10) SBR latex by mass of cement were prepared by modifying control concrete. Since the SBR latex used in this study contained 50%of water editor@iaeme.com

3 Sl.No MIX Cement in Kg FA in Kg CA in Kg Water in litre Polymer in litre Fiber in percent Slump in mm P. Palson and K. Manimaran required to be added in the concrete was accordingly adjusted. Some additional percentage of water to mass of binder also adjusted to maintain the slump between 50-75mm. Concrete mixtures was designed with latex modification and three mixtures of latex and steel fibre. The control concrete mix modified with 10% latex was modified with addition 0.5% steel fibre (CP 10 SF 0.5 ), 1.0% steel fibre (CP 10 SF 1.0 ) and 1.5% steel fibre (CP 10 SF 1.5 ) and without polymer and 1. %steel fibre (CSF 1.0 ).The details of mix were presented in Table.1 Table 1 Mix proportions of concrete 01 C CP CP 10S F CP 10S F CP 10S F CSF 1. 0% Test Details The weighed ingredients for the batch were mixed in a tilting drum type concrete mixture machine. The test specimens for compression (150 x 150 x 150mm cube), flexural strength (100 x 100 x 500mm prism),and modulus of elasticity of the concrete (150mm dia x 300mm height cylinder), and 125 x 250 x 3200mm beams were cast in steel moulds with mould releasing agent applied. The fresh concrete mix was filled in the steel mould in three equal layers and each layer was well compacted using table vibrator. Before the initial setting time of the concrete, top surfaces of the specimens were levelled using finishing trowel. The conventional concrete specimens were demoulded after 24 hours of casting and then moist cured for 28 days. The curing of latex modified concrete should be such that both hydration of cement and polymer formation take place yielding a strong co-matrix of hydrated cement inter penetrated by polymer film. While the hydration process is promoted by presence of moisture, film formation takes place only on drying. Therefore, the curing protocol for LMC specimens involves a combination of moist curing to promote cement hydration followed by drying to promote film formation. The latex modified cement concrete specimens were subjected to 2 days moist curing, 5 days water curing and 21 days air curing. 3. EXPERIEMENTAL INVESTIGATIONS 3.1. Mechanical Properties of Latex modified concrete Compressive Strength The compressive strength tests were conducted on a compression testing machine as per IS: The cubes 150mm sizes were tested at the age of 28 days. For each concrete editor@iaeme.com

4 Strength and Ductility of Polymer Modified Steel Fiber Reinforced Flexural Member composition three specimens were tested. Average value of three samples has been reported as compressive strength in Table 2.The compressive strength developments with respect to control concrete specimens at the age of 28 days cured are presented in Figure. 1 Table 2 Results of Compressive Strength S. No Mix Details Average Compressive Strength N/mm 2 1 C CP CP10SF CP10SF CP10SF CSF Flexural Strength Figure 1 Compressive Strength Development Concrete specimens of size 100mm x 100mm x 500mm were tested under standard four points bending in flexural testing machine. Specimens were tested at the age of 28 days. The flexural strength was calculated as the average of the three tested specimens and shown in Table 3. The flexural strength developments with respect to control concrete specimens at the age of 28 days cured are presented in Figure. 2 Table 3 Results of Flexural Strength S. No Mix Details Average Flexural Strength N/mm 2 1 C CP CP10SF CP10SF CP10SF CSF editor@iaeme.com

5 P. Palson and K. Manimaran Figure 2 Flexural Strength Development Stress Strain Curve Cylindrical specimens of size 150mm diameter and 300mm height were used for the determination of modulus of elasticity as per IS: Specimens were loaded uniaxial in a compression testing machine and deformations were recorded using dial gauge of 0.01mm least count at an interval of 10kN until the peak load. Stress strain curves obtained from cylinder compressive strength test were shown in Figure Flexural Test on Beams Figure 3 Stress Strain Curve The Experimental programme was consist of casting and testing of reinforced concrete beam of size 125mmx250mmx3200mm for all mix such as C,CP10,CP10SF0.5,CP10SF1.0and CP10SF1.5 Details of RC beam specimen section with reinforcement are shown in Figure 4. The reinforcement used was 2-12mm diameter Fe415 steel on the tension side and 2-8mm diameter in the compression zone. Test setup and typical tested specimens are shown in Figure 5 and Figure 6 respectively. The main objective of this study is to investigate the flexural behaviour and ductility of the conventional reinforced concrete beams and to improve the foresaid properties by the addition of latex and steel fibre. All the beam specimen were tested by applying 4 point static loading to have constant applied moment at middle of 1000 mm of an effective span of 3000mm.Load cell of 300kN with least count of 0.83 kn was used to measure the applied load. The load was applied in increments and each stage the following measurements were made. All the beams were simply supported and were loaded monotonically up to failure in four point bending editor@iaeme.com

6 Strength and Ductility of Polymer Modified Steel Fiber Reinforced Flexural Member (i) The deflection at mid span and one third portion from each support using a dial gauge having least count of 0.01mm. (ii) Demec gauge reading at mid span with 5 demec positions at top and 5 demec positions at bottom. (iii)crack width and crack growth was also noted along with the mode of failure for each test specimen. Crack width measured at the least count of 0.02mm. Details of test results are given in Table 7 and 8. The load versus deflection plot and moment versus curvature plot are shown in Figure 7 and 8. Energy absorption capacity of the beams could be obtained from load versus deflection curve of the specimens. Area under the load deflection considered in this study as energy absorption capacity of beams. This study adopted the ductility ratio defined by curvature at ultimate load to curvature at yield load. Results of energy absorption and ductility index are listed in Table 9. Cracking patterns of the tested beams at failure are shown in figure 6. Values of the load and crack width of all beams are listed in Table 10.The load versus crack width plot are shown in Figure mm Φ c/c 3200mm 125 mm 250 mm 3000 mm 2-8 mm Φ Figure 4 Details of RC Beam Specimens Figure 5 Test setup for beam Figure 6 Typical tested specimens Figure 7 Load Deflection Curve Figure 8 Moment Curvature Curve Figure 9 Load Vs Crack width editor@iaeme.com

7 P. Palson and K. Manimaran 4. RESULT AND DISCUSSION 4.1. Compressive Strength The compressive strength of control concrete, latex modified concrete and latex modified concrete with steel fibre were presented. It was observed that the latex modified concrete specimen showed 28 day average compressive strength of N/mm 2, at latex content of 10%. Latex modified concrete with steel fibre showed average compressive strength of order N/mm 2, N/mm2, N/mm 2 at fibre content of 0.5%, 1.0%, and 1.5% respectively, while the control concrete specimens had average compressive strength of N/mm 2. It could be observed from results that the compressive strength of concrete generally followed a decreasing trend with the latex. The compressive strength at 28 days decreased 14.55% with the latex content of 10%. The compressive strength of latex modified concrete with steel fibre increased 11.80%, 13.20%, 7.93% at the fibre content of 0.5%, 1.0%, and 1.5% respectively at 28 days. The reduction in compressive strength of latex modified concrete is due to the presence of rubber content as soft inclusion in the cement gel particles and increase in air content of latex modified concrete. Latex modified concrete with steel fibre improved the compressive strength of concrete compared to latex modified concrete. Physical interaction occurred due to the steel fibre and latex particles fill the existing spaces between the various granules of cement and those between the cement paste and the sand, which act as a filler reducing porosity cement matrix and densified structure due to the fibre and hence improvement in compressive strength Flexural Strength Addition of 10% latex in latex modified concrete increases the flexural strength to 16% at the age of 28 days. The Latex modified concrete with steel fibre ash showed an improvement of 21%,60%, and 61% at the latex content of 0.5%,1.0% and 1.5% respectively at the age of 28 days. A Significant flexural strength change was observed that mainly due to the fibre content which are providing tensile strength to the concrete and there is improvement in cement hydrate and aggregate bond because of decrease in w/b ratio and the high tensile strength of latex films present in latex modified concretes. Flexural strength depends mainly on the adhesion of aggregate grains and cement matrix. For latex modified concrete, creation of polymer membrane has a double role, that is increase the adhesion between the aggregate grains and cement matrix and fibre content prevent progressive development of initial micro cracks Elasticity modulus Stress strain characteristics of latex modified cylindrical specimens in compression obtained from load controlled tests compared to the control mix. It was observed that the stress strain plot of latex modified concretes were more deformability and similar trend to that of control specimens. The latex modified concrete and LMC with fibre showed higher moduli compared to control concrete 4.4. Flexure Behaviour of Beam The load deflection behaviour and moment curvature of test beams were investigated during the experiment. In the pre-cracking stage, the rate of deflection increase is small and increase linearly. This is expected since the strains in the steel and concrete are relatively small. In the case of concrete specimens without latex, crack appeared as the loading reached the first crack load of the specimen. Further increase of load resulted in the formation editor@iaeme.com

8 Strength and Ductility of Polymer Modified Steel Fiber Reinforced Flexural Member of additional cracks and widening of earlier cracks. Loading the beam until the ultimate stage, most of the cracks propagated towards top of the beam. In the case of specimens with latex large number of cracks developed. Latex modified concrete beams and latex modified with fibre specimen showed less crack Behaviour. Addition of latex and fibre improved the first crack load. At ultimate load the deflection was found to be higher. Referring to the experimental results following observations may be noted. Specimens with latex alone showed no significant improvement in ultimate load whereas specimens with fibre showed improvement in ultimate load. In latex modified concrete with fibre specimens, addition latex fills the voids present in concrete and improves the bond strength of the concrete and improves the bod between fibre and concrete. Hence an improvement in the first crack load and ultimate load was noticed. Referring to load deflection and moment curvature curve, all curves are linear up to the first crack and then they become non-linear due to the formation of multiple cracks and propagate further upto ultimate load. Addition of latex and fibre controls the widening of cracks. 5. CONCLUSIONS (i) The reducing effect of latex addition on compressive strength of latex modified concrete could be attributed to incorporation of soft rubbery material in the matrix. The strength reduction is found to decrease with steel fibre content. And hence steel fibre can be used for compensating the strength reduction due to latex addition. (ii) Flexural strength increased with the polymer addition and steel fibre (iii)elastic modulus decreased over unmodified concrete tendency is in agreement with increased deformability of latex modified concrete over unmodified concrete. The addition of fibre in latex modified concrete beam increases the ductile behaviour. (iv) Addition Latex and fibre improved the first crack load. (v) However load carrying capacity is only marginally improved. The addition of latex in concrete flexural members improves the cracking behaviour significantly REFERENCES 1. ACI committee 548 Guide for the use of polymer in concrete. ACI material journal, Vol83, no. 5, 1986 pp Alessandra.E.F, de s. Almeida (2007), Experimental study on polymer modified mortars with silica fume applied to porcelain tile, Building and Environment 42, 2007 pp Alessandra. E.F, de s. Almeida (2007), Mineralogical study of polymer modified mortar with silica fume, Construction and Building Materials 20,2006 pp Barluenga. G, Hernandez-Olivars. F,(2004) SBR latex modified mortar rheology and mechanical behaviour, Cement and Concrete Composites, Vol. 34, 2004, pp Bureau of Indian Standards IS 10262:2009, Recommended Guideline for Concrete Mix Design. 6. Bureau of Indian Standards IS 456:2000, Code of Practice for Plain and Reinforced Concrete. 7. Bureau of Indian Standards, IS 2386:1963, Part 3 Method of Test for Aggregates for Concrete Specific Gravity, Density, Voids Absorption and Bulking editor@iaeme.com

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