论文部分内容阅读
Phase conversion phenomena are often observed in calcium aluminate cements (CACs), when the water-rich hydrates (e.g., CAH10, C2AHs) formed at early ages at temperatures <30℃, expel water in time to form more compact, less water-rich structures (C3AH6).The phase conversions follow a path regulated by the thermodynamic stabilities (i.e., solubilities, Ksp) of phases.Based on this premise, it is demonstrated that conversion phenomena in CACs can be prevented by provoking the precipitation of phases more stable than those typically encountered along the conversion pathway.Therefore, X-AFm formation (where in this case, X =NO3) provoked by the sequential addition of calcium nitrate (CN) additives is identified as a means of preventing conversion.A multi-method approach comprising x-ray diffraction and evaluations of the compressive strength is applied to correlate phase balances and properties in CAC systems cured at 25℃ and 45℃.The results highlight the absence of the C3AH6 phase across all the systems and curing conditions considered, with no decrease in strength being noted, when sufficient quantities of CN additives are used.The experimental outcomes are fully supported by new insights gained from thermodynamic simulations which highlight thermodynamic selectivity as a means of regulating/controlling the evolutions of solid phase balances using inorganic salts in CACs, and more generally in cementitious material systems.