Effect of basalt fibers on mechanical properties of calcium carbonate whisker-steel fiber reinforced concrete

Abstract

Nowadays, hybrid fiber reinforced concrete is being considered for structural applications due to its enhanced mechanical properties compared to concrete without fibers/plain concrete. In this work, the mechanical properties of new kind of hybrid fiber reinforced concrete, i.e. CaCO3 whisker-steel fiber-basalt fiber reinforced concrete (CSBFRC) with various basalt fibers percentages are studied. All the fiber-reinforced concretes are compared with that of plain concrete (PC). The CaCO3 whisker, steel and basalt fiber lengths are 20–30 μm, 35 mm and 12 mm, respectively. Steel fibers and CaCO3 whiskers contents are 0.32% and 0.9%, by volume, respectively. Various basalt fiber contents of 0.34%, 0.68%, 1.02% and 1.36%, by volume, are added. For each batch, cylinders and beam-lets are cast and tested under respective compressive, splitting tensile and flexural load as per ASTM standards. Stress-strain curves and load-deflection curves are obtained. Strengths, energy absorptions and toughness indices are determined against for each type of loading. The scanning electron microscopy (SEM) analysis is performed to reveal the behavior (interfacial bonding) of CaCO3 whiskers, basalt fibers and steel fibers. It is concluded that, with increasing content of basalt fibers up to 0.68%, there is an increase in the mechanical properties of hybrid fiber reinforced concrete and CSBFRC4 is found to be an optimum. However, beyond 0.68%, the mechanical properties of CSBFRC decrease with an increase in the basalt fiber content. The resistance against cracking provided by hybrid fibers is observed by SEM images.