Determination of optimum fiber content for fiber reinforced micro concrete

Abstract

Fiber Reinforced Concrete is one of the most promising construction techniques and repairing materials of modern times. Polyester and steel fibers are, by far, the front runner in the field of reinforcing fibers. A very recent investigation on the properties of locally available Galvanized Iron wire (GI wire) which is basically mild steel wire with a thin coating of Zinc has discovered that it has the potential to be a viable lowcost alternative of commercially available steel fibers. Besides that, polyester fiber has been used as popular reinforcing material from long ago. On the other hand, Micro concrete technology is a new trend where the size of coarse aggregate is reduced significantly without compromising the strength of concrete. Here along with strength, workability is ensured using chemical admixture (Super plasticizer).Now a days it is mainly used for retrofitting purposes for its various inherent characteristics. Therefore, a research has been conducted to study the performance of locally available GI wire fiber reinforced Micro concrete (GWRMC) and Polyester fiber reinforced Micro concrete (PFRMC) and also make comparison to find the suitable option for our country. This paper presents the findings of several basic characteristics of GWRMC and PFRMC primarily related to strength, ductility and durability. The prime focus of the study was on the effect of fiber content on the foregoing properties of Micro concrete. Consequently, within the scope of the work, fiber dosage was varied within low range (1 to 2.5% by weight for GWRMC and 0.1 to 0.5% by volume for PFRMC) while the concrete mix-design and fiber properties were kept unchanged. A wide variety of tests including compressive and splitting tensile strength, modulus of elasticity and water absorption test (Sorptivity) were performed on suitable test specimens. It was observed for polyester fiber compressive strength increases upto 43 percent and splitting tensile strengths increases upto 30 percent with respect to control. Again for steel fiber compressive strength increases upto 47 percent and splitting tensile strengths increases upto 25 percent with respect to control. Durability test i.e. Sorptivity revealed that water absorption rate of Micro concrete is significantly lower than normal concrete. Furthermore, cost analysis and comparison of both types of fiber shows that the use of GI wire fiber instead of polyester fiber is little bit economical and convenient from the perspectives of Bangladesh.