Improving the carbonation performance of sulfate-activated material cured waste sediments by calcined Mg-Al hydrotalcite: Influence of CLDH dosages, carbonation concentrations and cycles

Abstract

A method was proposed to strengthen the carbonation resistance of the waste sludge matrix by replacing part of cement with industrial by-products such as ground-granulated blast-furnace slag (GGBFS) and fly ash (FA) via the structural recrystallization and anion exchangeability of calcined Mg-Al hydrotalcite in a humid carbon dioxide environment. The mechanical and workability results showed that although the addition of CLDH weakened the flow extension of the mixture samples, they accelerated the solidification and hardening of the samples and increased the development of compressive strength in a slightly carbonized environment (e.g., C5T3L0.3 and C5T3L0.6). Furthermore, XRD, TG, BSE, and MIP techniques were used to analyze the composition of the hydration products and the distribution of the pore structure of the CLDHs-containing samples at different carbonation times and carbonation concentrations. The results indicated that CLDHs had good carbon sequestration capability. The addition of CLDH helped to refine the pores, and a slightly carbonized product like calcium carbonate could enhance the strength development by filling the pores, but too much had side effects. The outcomes of the study also provided an alternative way of thinking about the anti-carbonation behavior of cement pastes.