Evaluation of waste concrete recycled powder (WCRP) on the preparation of low-exothermic cement

Adjusting the cement hydration process to reduce the heat release of cement was hotspots. Waste concrete recycled powder (WCRP) was produced by crushing construction wastes, which had the potential to change the hydration process for the existence of C-S-H particles. However, the effect of performance and mechanism of WCRP acting as supplementary cementitious material on low-exothermic cement was still unclear. Here, we crushed waste concrete to obtain WCRP, and then prepared the mixing pastes of WCRP and ordinary Portland cement. The hydration heat, compressive strength, and microstructure of the pastes were studied. The results indicated that WCRP decreased the hydration heat of cement pastes. The compressive strength increase rate with hydration heat for cement pastes containing WCRP indicated a good linear relationship. When the content of WCRP was less than 30%, the early compressive strength of cement pastes changed slightly. This is due to the new cement hydrates rebinders with WCRP particles. The microstructure analysis showed an increasing pores content and unchange of hydrates after WCRP addition. Fly ash (FA) and silica fume (SF) can enhance the hydration degree of WCRP pastes, and then improve the compressive strength. This study provided a reference for the application of WCRP in the preparation of low exothermic cement.

Automated summary

This study found that waste concrete recycled powder (WCRP) can reduce the hydration heat of cement pastes, and there is a linear relationship between the compressive strength increase rate and hydration heat for cement pastes containing WCRP. When the content of WCRP is lower than 30%, the early compressive strength of cement pastes remains relatively stable. Additionally, fly ash and silica fume can enhance the hydration degree of WCRP pastes and improve the compressive strength.