Steel fibre-reinforced high-strength concrete incorporating copper slag: Mechanical, gamma-ray shielding, impact resistance, and microstructural characteristics

Abstract

Copper slag (CS) is a hazardous by-product of copper manufacture and its disposal has resulted in serious environmental issues. In this study, the gamma-ray shielding capacity and impact resistance as well as the density, mechanical and microstructural properties of concrete mixes in which natural sand was partially replaced with CS at 20%, 40%, and 60% (by weight) were evaluated. The mixes were prepared with water to binder (w/b) ratios of 0.35 and 0.40. Steel fibres (SF) were also incorporated at volume fraction of 1.0%. As expected, mixes with a higher w/b ratio showed higher workability and lower strength and radiation shielding properties. The mechanical properties were improved with increasing replacement ratios of CS. The compressive strength of CS concrete increased by 5–12% relative to that of the control concrete. SF-reinforced concrete showed 27% and 25% higher splitting tensile and flexural strengths, respectively, compared to those of the counterpart unreinforced concrete. The linear attenuation coefficient of concrete specimens subjected to IAEA 137Cs (662 keV) point source was higher in mixes with lower w/b ratio and higher CS content and up to 42% enhancement in the linear attenuation coefficient was obtained at CS content of 60% and w/b ratio of 0.35. However, the effect of SF was not significant. On the other hand, SF-reinforced mixes with 60% CS exhibited about 40% higher impact resistance compared to its corresponding unreinforced mix. The microstructural properties of selected mixes were studied using scanning electron microscopy (SEM). CS concrete showed a denser matrix with fewer pores compared to the control concrete. Based on the experimental results, the use of 60% CS yields the best properties of high-strength concrete; however, it increases the unit weight beyond normal-weight concrete.