Investigation on the Effect of Recycled Concrete Powder in Alkali-activated Cementitous Materials

The recycled concrete powder (RCP)contains a large amount of SiO2,CaO,Al2 O3 and a small amount of unhydrated cement,which can be used as supplementary cementing materials (SCMs)through physical or chemical excitation. The resource utilization of recycled concrete powder is of great significance to save raw materials and dispose of waste. In this work,alkali-activated cementitious materials with different RCP substitution rates were prepared,and their fluidity,mechanical properties,microscopic characterization and hydration process were studied. The results show that the addition of RCP improves the fluidity of alkali-activated cementitious materials,and the fluidity of alkali-activated cementitious materials increase by 2%—12% at 10%—40% substitution rate. When RCP content is 10%,the compressive strength of alkali slag cementitious material increase by 13%. Inactive particles in RCP fill the pores and form dense microstructure. Since the inactive particles in RCP hinder the reaction between alkali solution and slag,the introduction of RCP delays the emergence of the second exothermic peak and decreases the early exothermic rate of alkali-activated cementitious materials. © 2023 Cailiao Daobaoshe/ Materials Review. All rights reserved.