The influence of curing methods on the performance of recycled concrete powder artificial aggregates and concrete

Abstract

In order to address the issues of pollution from waste concrete powder and alleviate the shortage of natural aggregates, recycled concrete powder (RCP) was used to produce artificial aggregates (RCPA). The effects of internal and external addition alkaline activator methods, as well as natural curing (20 °C), heated curing (20/40/60/80/100 °C), and steam curing (20/40/60/80/100 °C) on the properties of RCPA were investigated. It was found that the internal addition method was more effective; the heated curing method yielded the best results, with the optimal temperature being 60 °C. The highest strength of RCPA was 10.24 MPa, with a water absorption rate of 8.68 % at this point. The microstructure of the aggregate under heated curing showed significant improvement compared to that under natural curing. Concrete was prepared using aggregates cured naturally at 20 °C (20 °C NCA) and aggregates cured at 60 °C (60 °C HCA). It was found that the mechanical properties of concrete made with 60 °C HCA were superior to those made with 20 °C NCA. The compressive strength of recycled concrete powder artificial aggregate concrete (RCPAC) at 28d reached 83.73 %-89.97 % of that of natural concrete (NC), with a density lower than NC. When subjected to compression, only mortar and interfaces in NC were damaged, whereas aggregates in RCPAC were also damaged. The resistance drying shrinkage and freeze-thaw of RCPA (ellipsoidal) concrete are better than those of natural aggregate (polyhedron) concrete. The 60 ℃ HCA concrete is optimal, enduring up to 250 freeze-thaw cycles. RCPA can replace natural aggregates in concrete production, and durability is crucial; therefore, future research should explore this area more thoroughly.