Experimental and analytical study of steel and chopped glass fibre reinforced concrete under compression

Fibres have been used in concrete mixtures for many applications to improve performance. Fibres bridge cracks which enhances peak, post-cracking, and toughness responses. Understanding the compressive behaviour of Fibre Reinforced Concrete (FRC) is important for the structural design of compressive members including columns, piers, and compressive struts of beams. An experimental and analytical investigation was carried out to evaluate the compressive response of FRC. A total of 50 cylinders (100 x 200 mm) were tested in compression to evaluate the effect of adding steel and/or glass fibres with three dosages (0.5%, 1.0%, and 1.5% by volume fraction) on compressive strength; modulus of elasticity; Poisson's ratio; yield, peak, and ultimate strains; and toughness index. Since adding fibres affects concrete's stress-strain relationship, a new concrete compressive stress-strain relationship that accounts for the effect of steel and glass fibres is proposed. This study also presents new design-oriented expressions for equivalent stress block parameters that consider fibre influence. Results indicate that adding fibres significantly increases peak stress, yield strain, ultimate strain, and toughness index though the modulus of elasticity was unaffected. The proposed model was found to give a good, though the conservative representation of the measured stress-strain response with experimental to predicted ratios between 1.00 and 1.13 and a coefficient of variation between 5% and 14%.