Investigation on the reactivity of recycled brick powder

Abstract

Knowing the reactivity of recycled brick powder (RBP) is fundamental for its correct and efficient utilization. In this work, the dissolution behavior of RBP in NaOH solution and the degree of reaction in cement matrix were studied to investigate the reactivity of RBP. The results revealed that the main active species of RBP, Si and Al, showed obvious lasting dissolution with a significant non-steady state dissolution stage, indicating that the reaction proceeds slowly. The dissolution mechanism controlled by the phase boundary reaction, with activation energies of 82.74 kJ/mol and 75.79 kJ/mol for Si and Al dissolution, respectively, further confirmed this finding. The strength activity index, thermogravimetric analysis, selective dissolution, BSE-IA-Mapping and MAS NMR all confirmed reactivity of RBP. Additionally, reaction rims were observed around RBP particles in cement paste. The low Ca/Si and Ca/Al ratios and their significant increases in a direction from the particle boundary to the paste demonstrate that the rim was a hybrid phase composed of the original RBP components and the reaction products.