Ductility of steel-fibre-reinforced recycled lightweight concrete

Abstract

This work examines experimentally and numerically the influence of steel fibre reinforcement on lightweight aggregate concrete (LWAC). The replacement of conventional aggregates with recycled lightweight ones has several benefits such as reducing the mass of the structure leading to more economical designs (also beneficial under earthquake loading). The experimental project showed that it was possible to produce higher strength to weight ratio of LWAC compared to normal weight aggregate concrete (NWAC) as dry densities were approximately 700 Kg/m3 lower for identical characteristic compressive strengths between 40MPa and 30MPa. This could lead to savings in materials, construction and transportation costs making it especially useful and economical for long-span and seismic-resistant structures. Conversely, LWAC is noted for its highly brittle nature due to its associated weak aggregate interlock mechanism which can be typically compensated for by increasing shear reinforcement and dowel action by means of adding higher reinforcement ratios. Nonetheless, this creates several challenges in construction such as congestion of reinforcement in critical regions as well as increased dead loads which render LWAC use counterproductive. Thus, steel fibre reinforcement emerges as a promising solution where partial or total substitution of conventional transverse reinforcement could become a possibility. This project carries out examination of the effectiveness of hooked-end steel fibre reinforcement with fibre volume fractions of Vf = 1% and Vf = 2%. The experimental investigation includes the study of direct uniaxial compression and tension (unique pullout test) and indirect splitting and flexural tensile tests. Moreover, a nonlinear finite element study has been carried out using ABAQUS to model the experiments using CDP. Currently, there is no international standards or design guidelines for steel fibre reinforced lightweight concrete (SFRLC). This project will help address that and lead to sustainable and innovative seismic design solutions in the future.