Promoting the simultaneous reaction of carbonate and aluminate phases through anhydrous carbonation : improving the properties of sulfoaluminate cement and stabilizing ettringite

Abstract

This research introduced a novel method named anhydrous carbonation (AC), which was developed to enhance the performance of sulfoaluminate cement (SAC) and stabilize AFt via promoting the reaction between the in-situ generation of highly active calcium carbonate (HACC) and C4A3Š. The results indicate that AC accelerated the hydration process and significantly improved both the early and later compressive strength of hydrated samples. Specifically, compared to the reference (Ref) sample, the compressive strength of the AC-2h sample at 1d and 28d can be increased by up to 28.0 % and 27.2 %, respectively. AC altered the hydration kinetics of SAC, promoting the dissolution of clinker and the precipitation of hydration products. During the early hydration stage (1 day), C4A3Š reacted with water and formed AFm. Simultaneously, the HACC reacted with C4A3Š and produced monocarboaluminate (Mc), hemicarboaluminate (Hc). In the later hydration stage (28 days), AFm reacted with HACC, forming Mc and Hc, further stabilizing AFt. The performance enhancement of SAC after AC is primarily attributed to a pivotal “reaction window” between HACC and C4A3Š. This interaction synchronizes carbonate-aluminate reactions, facilitating Mc and Hc formation. The indirect stabilization of AFt, the provision of nucleation sites for hydration products by HACC, and the filler effect of HACC as an inert filler refined the pore structure and reduced the size of cement clinker particles.