Prospect of gold tailings as a new mineral admixture: Effect on hydration, pore structure and mechanical properties of concrete

Abstract

Gold tailings, with silica (SiO₂) as their primary component, have potential as a mineral admixture. To optimize the utilization of gold tailings while reducing cement consumption, this study investigates their substitution for cement. The effects on fluidity, setting time, mechanical properties, resistivity, hydration products, and pore structure of composite cementitious materials with different gold tailings substitution ratios are explored. Cost effectiveness of these composite concrete was also assessed. Results show that increasing gold tailings substitution moderately reduces fluidity and extends setting time. As low-activity admixtures, gold tailings slightly shorten the dissolution period while prolonging induction and acceleration periods of pastes. They do not alter the hydration product types of cement but improve hydration degree of cement. In the early stages of hydration, a high content of gold tailings increases the number of large-diameter pores. As hydration progresses, these pores are gradually filled by hydration products. Despite a gradual decline in early mechanical strength with increasing gold tailings content, this decline diminishes as hydration progresses at equivalent substitution ratios. Overall, a 10% substitution ratio of gold tailings has proven to be optimal, as the mechanical strength and porosity characteristics of the concrete at 28 d are comparable to those without gold tailings, while also offering similar cost benefits.