PROPERTIES IMPROVEMENT OF LEAN CONCRETE MIXES USING SILICA-FUME AND POLYMERS

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1 International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 9, September 218, pp , Article ID: IJCIET_9_9_136 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed PROPERTIES IMPROVEMENT OF LEAN CONCRETE MIXES USING SILICA-FUME AND POLYMERS Hayder Mohammed Jasim AL-Modern, Tagreed Hameed Khlif ALabedi, Layth Abdulrasool Mahdi Alasadi Faculty of Engineering, University of Kufa/Najaf ABSTRACT Lean concrete mixes is a concrete mix with low cement content and high percentages of aggregates, it used in several works such as the blinding concrete under foundations and as leveling course below footings or in mass concrete such as dams. The need to make this layer of concrete in more strength and more durable is important, using polymers such as styrene butadiene rubber ( SBR ) in concrete improve the mechanical strength of concrete and durability and make concrete permeability very low, and also using silica-fume powder leads also to improve the strength of concrete. This investigation studies the effect of using styrene butadiene rubber polymer in different percentages and also silica fume to lean mixes to improve the mechanical properties. Mixes with 1% polymers gives the highest values of mechanical properties with 1 % silica fume, it gives average compressive strength of 24.3 MPa while in reference mix give 13.2 MPa, the flexural strength also increased from 1.24 MPa for lean mixes to 4.8 MPa to silica-polymer mixes.the main reason for using polymers and silica fume is because of these two materials reduce the heat of hydration during mixing and casting concrete, so that is very important in mass concrete. Key words: lean concrete, styrene butadiene polymer, compressive strength, tensile strength, flexural strength Cite this Article: Hayder Mohammed Jasim AL-Modern, Tagreed Hameed Khlif ALabedi, Layth Abdulrasool Mahdi Alasadi, Properties Improvement of Lean Concrete Mixes using Silica-Fume and Polymers. International Journal of Civil Engineering and Technology, 9(9), 218, pp INTRODUCTION Using SBR polymers improve the mechanical properties and also durability and less permeable concrete [ 1, 2]. Lean concrete mixes is a typical concrete which has low quantity of cement and can be used under footings or in mass construction where strength is not important [3], in some dams in united states using more than 2 kg per cubic meters leads to cracks in dams because of large quantities in heat of hydration, it lowered to 167 kg per cubic editor@iaeme.com

2 Hayder Mohammed Jasim AL-Modern, Tagreed Hameed Khlif ALabedi, Layth Abdulrasool Mahdi Alasadi meter [ 3]. Sometimes lean concrete mixes may be subjected to attack of groundwater that contains harmful salts, so the lean mix can have damaged. This investigation deals with improving some mechanical properties like compressive, tensile and flexural strength by adding polymers and silica fume, that highly increase the properties of low cement content or lean mixes of concrete and these two materials reduce voids and decrease permeability and make lean concrete more durable. And another important thing of using polymers and silica fume in this study is the heat of hydration which reduces by using SBR polymers [ 4 ] and also silica fume which give more increment in strength and reduce the heat of hydration [ ] which is very important in mass concrete construction such as dams. 2. EXPERIMENTAL PROGRESSES 1- materials: sulfate resistance cement used in all mixes, fine aggregate with zone 1 as shown in table 1 is used and 2 mm maximum size aggregate used as sown in table 2 confirm with IS-383 [ 6]. 2- tests: compressive, tensile and flexural tests were done, the compressive strength done by using steel molds with 1*1*1 mm, and using 3 specimens for each mix and taking the average value, tensile strength done by using splitting test for 1*2 cm cylinders and flexural strength done by using prisms of 1 *1*4 cm and third point loading test. figures 1 and two show flexural and compressive strength tests. Table 1 grading of coarse aggregates according to IS-Standards Sieve size, mm Percentage passing by weight Percentage passing, IS - Standards Table 2 Grading of fine aggregates according to IS-Standards Sieve size, mm Percentage passing by weight Percentage passing, IS Standards zone 1 1 mm 1 1 mm mm mm micron micron micron RESULTS AND DISCUSSIONS Tables 3 and 4 shows all the mixes used in the study, table 3 shows lean mixes modifies with % silica fume admixture and different percentages of SBR polymers starting from 2% to 1 %, it can be seen that compressive strength improved the low compressive strength(13.2 MPa) for reference mix to 22.7 MPa with 1% polymers and constant value of silica fume of %, this can be attributed by the effect of polymers particles which forms polymer films inside concrete, and this film bonds with cement particles and external silica surface of aggregates [7], also silica fume react with cement hydration compounds like calcium hydroxide and forming additional cement paste or calcium silicate hydrate (C-S-H)which caused extra strength and decrease permeability to concrete, [8, 9]. Figures ( 3 to 8) show the editor@iaeme.com

3 Properties Improvement of Lean Concrete Mixes using Silica-Fume and Polymers relationship between polymer/cement ratio and compressive, tensile and flexural strength of lean mix concrete with mathematical models, the relations show straight lines relationship and show the improvement by adding polymers to mixes. tensile strength increased from 1.8 MPa to 2.8 MPa by adding 1% SBR polymer (for % silica fume) and increased to 2.92 MPa for 1% silica fume, flexural strength increased highly from 1.24 MPa to 4.11 MPa and to 4.8 MPa for % and 1 % silica fume mixes respectively, and that attributed to high bond of SBR films that formed inside concrete which bonds with silica of aggregates and cement gel particles and also attributed to high tensile strength of the polymers films itself [ 1] which ranged between 18 2 MPa. Table 3 Mechanical behavior for lean concrete improved with SBR and silica-fume powder. Mix Comp strength Tensile strength Flexural strength 1:3:6 ref :3:6, 2% polymer :3:6, 4% polymer :3:6, 6% polymer :3:6, 8% polymer :3:6, 1% polymer Table 4 Mechanical behavior for lean concrete mix improved with polymers and 1 % silica-fume powder. Mix Comp strength Tensile strength Flexural strength 1:3:6 ref :3:6, 2% polymer and 1% silica fume 1:3:6, 4% polymer and 1% silica fume 1:3:6, 6% polymer and 1% silica fume 1:3:6, 8% polymer :3:6, 1% polymer and 1% silica fume Figure 1 Flexural strength test for lean mix concrete (third point loading) editor@iaeme.com

4 Compressive strength(mpa) Hayder Mohammed Jasim AL-Modern, Tagreed Hameed Khlif ALabedi, Layth Abdulrasool Mahdi Alasadi Figure 2 Compressive strength test for lean mix concrete Compressive strength with different polymer ratio and constant % silica fume y =.9699x R = Figure 3 Relationship between polymer/cement ratio and compressive strength of lean mix concrete (with % silica fume) Figure 4 Relationship between polymer/cement ratio and tensile strength of lean mix concrete (with % silica fume) editor@iaeme.com

5 Tensile strength(mpa) Compressive strength(mpa) Flexural strength(mpa) Properties Improvement of Lean Concrete Mixes using Silica-Fume and Polymers Flexural strength with different polymer ratio and constant % silica fume y=.2667x R² = Figure Relationship between polymer/cement ratio and flexural strength of lean mix concrete (with % silica fume) Compressive strength with different polymer ratio and constant 1% silica fume y=1.144x R² = Figure 6 Relationship between polymer/cement ratio and compressive strength of lean mix concrete (with 1% silica fume) Tensile strength with different polymer ratio and constant 1% silica fume y=.164x R² = Figure 7 Relationship between polymer/cement ratio and tensile strength of lean mix concrete (with 1% silica fume) editor@iaeme.com

6 Flexural strength(mpa) Hayder Mohammed Jasim AL-Modern, Tagreed Hameed Khlif ALabedi, Layth Abdulrasool Mahdi Alasadi Flexural strength with different polymer ratio and constant 1% silica fume y=.36x R² = Figure 8 Relationship between polymer/cement ratio and flexural strength of lean mix concrete (with 1% silica fume) 4. CONCLUSIONS The 1- In previous studies, the polymer SBR and silica fume admixtures reduce the heat of hydration of cement, so that is very important to mass concrete construction and this point attribute the reason of using these two materials in this study. 2- polymer SBR and silica fume increase values of mechanical properties such as compressive, tensile and flexural strengths, and using 1% silica fume and 1 % SBR polymer give maximum strength to lean mixes. 3- compressive strength increased from 13.2 MPa to 24.3 MPa, tensile strength increased from 1.1 to 2.9 MPa, and flexural strength increased from 1.2 MPa to 4.8 MPa, by using SBR polymers and silica fume, and these increments attributed to the action of both sbr which bonds strongly with silicates and cement gel, and also the action of silica fume which reacts with calcium hydroxide which liberates from cement hydration, and forming another active gel which reduces voids inside concrete and gives additional strength. REFERENCES [1] Kapil, E., Performance analysis of styrene-butadiene rubber latex on cement concrete mixes, an international journal of engineering research and applications, vol 4, issue an 3, 214, p.p [2] Omprakash, S and hired, S., Review On Polymer Modified Concrete and its applications to concrete structures, International Journal of engineering research, vol issue special 3, Feb. 216, p.p [3] ACI-27.1R-96, Mass Concrete,Report of ACI-Committee 27, 1996,p.p [4] Xiaoling, Q. Influence of SBR latex and HPMC on the cement hydration at an early age, case studies on construction materials journal homepage, ccm, vol 6, June 217, p.p [] Zhang, M., Effect of silica fume on cement hydration and temperature rise of concrete in the tropical environment, the IES Journal Part A: Civil and Structural Engineering, vol 1 issue 2, editor@iaeme.com

7 Properties Improvement of Lean Concrete Mixes using Silica-Fume and Polymers [6] IS 383, Indian standards specifications for coarse and fine aggregates, Affirmed, 22, 2p. [7] Alnuman, B., and Ibrahim, A., stress-strain relationship of polymer modified concrete, Iraqi journal for civil engineering, June 2. [8] borsaikia, A., Effect of silica fume on some properties of concrete, Research Gate, March 21, p.p 1-7 [9] Bayasi, z, and Zhou, j., Properties of Silica Fume Concrete and Mortar, ACI Material Journal, Vol 9, no. 4, July- August [1] Wikipedia, the free Encyclopedia Styrene Butadiene, 23 March 218,