TA616 : Experimental investigation of the effect simultaneously addition of steel macro fibers and polypropylene micro fibers on the mechanical propertis of concrete containing recycled aggregates
Thesis > Central Library of Shahrood University > Civil & Architectural Engineering > MSc > 2021
Authors:
Sadegh Ghasemi [Author], Jalil Shafaei[Supervisor], Meysam Jalali[Supervisor]
Abstarct: Concrete is known as the second most used material in the world after water due to its benefits and advantages. As the consumption of concrete increases, of the mines natural aggregates decrease. This highlights the need to replace recycled aggregates with natural aggregates. In this study, recycled aggregates have been replaced by natural aggregates in proportions of 25% and 50% by weight. Replacing recycled aggregates with natural aggregates cause to reduces the mechanical properties of concrete. To compensate for the reduction of mechanical properties of concrete due to the replacement of aggregates by the simultaneous addtion of steel fibers of 0.5 % and 1% by volume fraction and 0.4 % by volume fraction of polypropylene fibers in the sample Concrete. Has been used. A total of 12 mixing designs were tested for compression strength, Brazilian tension strength and flexural strength by four-point bending. In this Experimental study, factors such as wear percentage of natural and recycled aggregates, moisture content and water absorption of recycled and natural aggregates, aggregate density, specific gravity of fresh concrete, compressive strength, tensile strength, modulus of elasticity, peak loads, fracture modulus, flexural stiffness and equivalent flexural strength were investigated. The results show that the replacement of 25% and 50% of recycled aggregates with natural aggregates cause to reduces 14% and 15% of compressive strength, 3% and 13% Brazilian tensile strength and 10% and 12% modulus of rupture are observed compared to concrete, respectively. Also, adding 0.4 % of polypropylene fibers to the control concrete increases 1.52% of the compressive strength, 1.46% of the tensile strength and 33% of the rupture modulus. In case of simultaneous addition of 0.4 % polypropylene fibers with 1% steel fibers to concrete without recycled aggregates, it increases the compressive strength by 3%, the Brazilian tensile strength by 26% and the modulus by 66%, respectively. Rupture is observed in relation to concrete. Which shows that steel fibers are more efficient in improving the tensile and flexural strength of concrete than polypropylene fibers. Also, reinforced concrete with hybrid fibers does not break after breaking, and the fibers play an important role in maintaining the cohesion of the concrete.
Keywords:
#Recycled aggregates concrete #Fiber reinforced concrete #Steel fibers #Polypropylene fibers #Four-point bending. Keeping place: Central Library of Shahrood University
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