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将水灰比为0.45硫铝酸盐水泥净浆试件半浸泡在装有10%Na_2CO_3溶液中的容器中,分别在(20±2)℃,湿度(60±5)%的稳定环境中和循环变化条件下[先在(30±2)℃、湿度(80±5)%的环境保持24 h、再在(20±2)℃、湿度(60±5)%的环境保持24 h]研究其盐结晶破坏特征。结果表明:稳定环境下暴露72 d后,试件水分蒸发区表面出现了Na_2SO_4晶体,但并没有出现严重的盐结晶破坏;循环变化环境下,只经过4个循环8 d的侵蚀,试件水分蒸发区发生了严重的层状结晶破坏。其破坏机理是硫铝酸盐水泥水化产物与碳酸钠之间化学侵蚀生成物Na_2SO_4结晶破坏所致,并没有出现Na_2CO_3结晶破坏。如果胶凝材料水化产物与盐溶液之间存在化学反应,虽然环境条件满足盐结晶发生的要求,但化学侵蚀生成物结晶膨胀才是导致净浆或者混凝土试件水分蒸发区破坏的原因。
The water-cement ratio of 0.45 sulphoaluminate cement was semi-soaked in a container filled with 10% Na 2 CO 3 solution in a stable environment of (20 ± 2) ℃ and humidity (60 ± 5)% respectively Under the condition of cyclic change, [24 h at (20 ± 2) ° C and 60 ± 5% humidity] was maintained for 24 h at (30 ± 2) ° C and 80 ± 5% humidity Its salt crystallization damage characteristics. The results showed that Na_2SO_4 crystals appeared on the surface of water evaporation zone after exposure for 72 d in a stable environment, but no serious salt crystal destruction occurred. Under the cyclic change environment, only 4 cycles of 8 days erosion, Evaporation zone occurred serious stratified crystallization damage. The failure mechanism is due to the destruction of Na_2SO_4, which is a chemical attack product between sulphoaluminate cement hydrate and sodium carbonate, and no damage of Na_2CO_3 crystallizes. If there is a chemical reaction between the hydration product of the cementitious material and the salt solution, although the environmental conditions meet the requirements of salt crystallization, the crystal expansion of the chemical attack product causes the destruction of the water evaporation zone of the paste or the concrete specimen.