Experimental Study on the Mechanical Properties of Polypropylene Fibre Reinforced Self Compacting Concrete with Portland Slag Cement

Abstract

Concrete is acknowledged to be a relatively brittle material when subjected to normal stresses and impact loads, where tensile strength is only approximately one tenth of its compressive strength. As a result for these characteristics, concrete member could not support such loads and stresses that usually take place on concrete beams and slabs. Historically, concrete member reinforced with continuous reinforcing bars to withstand tensile stresses and compensate for the lack of ductility and strength. Furthermore, steel reinforcement adopted to overcome high potential tensile stresses and shear stresses at critical location in concrete member. The inclusion of steel reinforcement significantly increases the strength of concrete, but to produce concrete with homogenous tensile properties, the development of micro cracks is a must to suppress. The introduction of fibres was brought in as a solution to develop concrete in view of enhancing its flexural and tensile strength. It is a new form of binder that could combine Portland cement in the bonding with cement matrices. Fibres are generally discontinuous, randomly distributed throughout the cement matrices. Fibre reinforced self-compacted concrete‟ (FRSCC) is formed from cement, various sizes of aggregates, which incorporate with discrete, discontinuous fibre

Self–compacting concrete (SCC)  is the concrete that is able to flow under that is able to flow in the interior of the formwork, filling it in a natural manner and passing through the reinforcing bars and other obstacles, flowing and consolidating under the action of its own weight. These properties enable the SCC to be an excellent material for constructions with complicated shapes and congested reinforcement. One of the main advantages in using SCC is the minimization of skilled labour needed for placing and finishing the concrete. All these benefits decrease the costs and reduce the time of the building process over constructions made from traditionally vibrated concrete. However, hardened self-compacting concrete is still as brittle as normal concrete and has a poor resistance to crack growth.To improve the post-peak parameters of SCC, polypropylene (Recron fibres) are added.

As self-compacting concrete offers several economic and technical benfits the use of polypropylene, polyester and glass fibres extends its possibilities. Polypropylene fibres bridge cracks, retard their propagation, and improve several characteristics and properties of the SCC. The purpose of thesis is to investigate the effects of weight fraction of polypropylene on the compressive strength, split tensile strength, and modulus of elasticity of polypropylene fibre reinforced self-compacting concrete.  For this purpose, Recron fibres were used. Four different fiber volumes were added to concrete mixes at 0.1, 0.2, 0.3and 0.4 percent by weight of cement. Four different mixes were prepared. After 28 days of curing, compressive strength, split tensile strength and modulus of elasticity were determined. It was found that, inclusion of polypropylene fibres significantly affect the compressive strength, split tensile strength and modulus of elasticity of self-compacting concrete.