Preparation of C/M−S−H cementitious materials from phosphate tailings and their dehydration and hydration mechanism

Abstract

Aiming to reduce the CO2 emission of the cement materials preparation, a novel strategy to fabricate C/M-S-H cementitious materials from phosphate tailings has been proposed. To reveal the dehydration and hydration behavior of C/M-S-H, an experimental program combining TG, XRD, SEM, and corresponding strength evaluation was performed. The agglomerate-shaped C-S-H and flake-shaped M-S-H were synthesized from phosphate tailings. The experimental results showed that the rehydration capacity of C-S-H increased and then decreased with the rise in temperature (200–600 °C). The basic structural framework of M-S-H was maintained below 400 °C and disrupted at 600 °C, where the rehydration capacity decreased sharply. The dehydrated M-S-H showed a structural recovery after rehydration. However, dehydrated C-S-H formed dense C-S-H particles on the surface after rehydration, increasing the accumulation volume in this region and improving early strength. Ultimately, appropriate dehydration temperatures and additions could increase early hydration reactivity, thereby enhancing the concrete.