Bending Properties of Polyvinyl Alcohol Fiber Cementitious Composite: Sample Thickness and Test Speed Effects

Fiber Bridging on the cracks is a known mechanism in the control of width of cracks & behaviour of composites. This mechanism is used in the fiber reinforced polymers, ceramics & recently cement composite. Brittle behaviour is the most important defect of concrete. Traditional Fiber Reinforced Concretes (FRC) doesn‟t change mechanical behaviour of concrete, although it increases ductility. In this Study, the presence of two different types of Polyvinyl Alcohol (PVA) fibers and its effect on the mechanical behaviour of composite was investigated. To study the tensile behaviour of specimens, four points bending test were used. PVA2 composites show higher strength and lower deflection relative to PVA1. The sign of slope in non-linear part of Stress-deflection curve was used as a novel way to evaluate the mechanical behaviour of specimens after first cracking, if it is positive Strain-Hardening behaviour is observed and if it is negative the composite has Stress softening behaviour. Decreasing the thickness and test speed caused two dimension arrangements of fibers and more Strain-Hardening behaviour was attained. PVA1 composites showed the ideal Strain-Hardening behaviour and multiple cracking despite PVA2 composites behaved the usual stress softening.

Keywords:

Engineered Cementitious Composites , Poly Vinyl Alcohol Fiber , Fiber Reinforced Concrete , Bending Test