CaCO3和CaSO4·2H2O共同作用下Ca2+对C3A水化浆体固化氯离子性能的影响

Role of Calcium Ion on Chloride Binding in Hydrated C3A Pastes Blended with CaCO3 and CaSO4·2H2O

采用平衡法研究了CaCO 3和CaSO 4·2H 2 O共同存在时Ca 2+对C3A水化浆体氯离子固化能力、生成产物和氯盐溶液pH值的影响.结果表明:C3A水化浆体固化氯离子后生成含氯铝酸盐并释放OH-,提高了氯盐溶液的pH值;CaCO 3和CaSO 4·2H 2 O分别作用时均会降低C3A水化浆体的氯离子固化能力和氯盐溶液pH值的提高程度,CaCO 3和CaSO 4·2H 2 O共同作用时则会显著降低C3A水化浆体的氯离子固化能力;C3A水化浆体中含氯铝酸盐生成量和氯离子固化能力随氯盐溶液pH值的降低而减小,而Ca 2+会降低氯盐溶液pH值的提高程度,但能提高C3A水化浆体的氯离子固化能力,CaCO 3或CaSO 4·2H 2 O单独存在时都能使Ca 2+提高氯离子固化能力的效果更为显著,且CaCO 3比CaSO 4·2H 2 O的作用更加明显,但CaCO 3和CaSO 4·2H 2 O共同存在时会出现负协同作用;在CaCO 3和CaSO 4·2H 2 O共同作用下,Ca 2+促进各水化产物与氯离子反应生成含氯铝酸盐的效果由小到大为:AFt<C3AH 6<AFm<碳铝酸钙水化物,同时改变了所生成含氯铝酸盐(固溶体)的物相结构.

Role of Ca2+on chloride binding in hydrated C3A pastes blended with CaCO3 and CaSO4·2H2O was investigated by chloride binding capacity,phase assemblages and pH value based on equilibration method.The results show that pH value increases as a result of the chloride binding by hydrated C 3 A pastes resulting in the formation of chloride-bearing AFm phases and release of OH-.Both of CaCO 3 and CaSO 4·2H2O leads to the decrease of chloride binding capacity and pH value,and combined incorporation of CaCO3 and CaSO4·2H2O causes significant reduction in chloride binding capacity specially.Reduction in pH value of chloride solutions decreases chloride binding capacity of hydrated C 3 A pastes by less formation of chloride-bearing AFm phases,while Ca 2+leads to lower pH value but higher chloride binding capacity.The promotion in chloride binding capacity by Ca 2+is more pronounced with incorporation of CaCO3 or CaSO 4·2H 2O but less notable with both of them,and effect of CaCO 3 is more severe.Ca 2+increases chloride binding capacity by promoting the transformation of hydrates in hydrated C 3 A pastes blended with CaCO 3 and CaSO4·2H2O to chloride-bearing AFm,with improvement of AFt<C3 AH 6<AFm<carboaluminate hydrates.The phase structure of chloride-bearing AFm which are solid solutions is affected.