Low carbon research in precast concrete based on the synergistic mechanism of red mud-ground granulated blast furnace slag powder

Abstract

The synergistic effect red mud (RM) and ground granulated blast furnace slag (GGBS) in cementitious materials has been widely reported, which is attributed to improve the performance of low-clinker cement. However, the existence of synergistic effect between RM and GGBS under high-temperature steam curing conditions has rarely been studied. In order to maximize the use of solid waste for the purpose of low carbon and conserving resources, 65% RM and GGBS were used to replace cement for the preparation of precast concrete, and two types of water/binder (W/B) ratios and steam curing temperatures were set to investigate the synergistic effect of multisolid waste under high-temperature steam curing conditions. With decreasing RM and increasing GGBS, the demolding strength of precast concrete samples cured by 60 °C with two different W/B ratios decreases, but the demolding strength rises and then decreases when the steam curing temperature is 80 °C. This suggests that the simultaneous use of two mineral admixtures in place of cement at 80 °C produces a significant synergistic effect and is able to increase the demolding strength of the samples by up to 50%. The change in compressive strength of precast concrete samples from 3 to 90 d is significantly different from the demolding strength. At a W/B ratio of 0.3, there is still prominent synergy between RM and GGBS after 28 d of hydration of precast concrete samples at both steam curing temperatures. In contrast, with a high W/B ratio (0.45), the synergistic effect is not evident throughout the period at either steam curing temperature. From the results of the whole experiment, synergistic effect between GGBS and RM is more pronounced at low W/B ratios or high steam curing temperatures. This study provides a new idea for the synergistic utilization of high-dose of multisolid waste in the preparation of precast concrete under high-temperature curing conditions.