Investigations on the rehydration of recycled blended SCMs cement

This paper intends to contribute to a better knowledge of the dehydration and rehydration of blended SCMs(SF, FA, GGBS, LS)-cement pastes. To this end, a comprehensive experimental program combining QXRD, TG, SEM, isothermal calorimetry, MIP and mechanical tests was performed. The thermal activation temperature (TAT) has a significant influence on the rehydration properties of recycled blended cement (RBC) pastes, in particular, different optimum TAT was obtained in different RBC with various precursor components, resulting in pastes with different microstructure and mechanical properties. The RBC paste is formed by a ‘dual structure’ composed by internal hydration products (rehydrated from porous RBC particles) and external hydration products (surrounding dispersed particles, primarily AFt and AFm). The reformation of C(-A)-S-H from the thermal-activated dehydrated amorphous phases is found to be responsible for the reactivity and strength gain of the RBC as a binder.