Enhancing temperature resistance of calcium aluminate cement through carbonated steel slag

The conversion from metastable phase to stable phase in calcium aluminate cement (CAC) caused by temperature increase can lead to an increase in porosity and a decrease in compressive strength. This study investigated the effects of carbonated steel slag (CSS) on the hydration, microstructure, and resistance to temperature fluctuations of CAC at temperatures ranging from 20 degrees C to 70 degrees C. The results showed that the incorporation of CSS leads to the formation of carbonate-AFm (or AFt) phases (hemicarboaluminate (Hc) and monocarboaluminate (Mc)). The increase of CSS content promotes the hydration of CA and CA2 to Hc and Mc (Hc/Mc), and weakens the hydration to C3AH6 and AH3 at 70 degrees C. Therefore, the impact of the conversion from CAH10 phase to C3AH6 phase on CAC is weakened. As the CSS content increases from 0 to 40 %, the loss of compressive strength of the samples decreases from 45.7 % to 10.4 % at 70 degrees C for 7 days, corresponding to a 77.2 % increase in temperature fluctuation resistance. Meanwhile, the addition of CSS can alleviate the increase in pore volume of CAC at 70 degrees C, and even lead to a decrease in CSS-40 sample.