石膏对碳硫硅钙石型硫酸盐破坏的影响

Effect of Gypsum on Thaumasite Form of Sulfate Attack

通过将内掺不同种类和不同质量分数二水石膏的水泥-石灰石粉净浆和胶砂试件在(5±1)℃的低温条件下长期浸泡,并定期观测试件外观形貌与抗压强度变化,同时对净浆试件取样进行X射线衍射和Fourier红外光谱分析,研究了石膏掺量对水泥基材料碳硫硅钙石(TSA)型硫酸盐破坏的影响及破坏机理。结果表明:当净浆试件中石膏掺量≥10%时发生了TSA型硫酸盐破坏,而石膏掺量为7.0%和3.5%的净浆试件均未发生破坏;水泥基材料中的石膏是否会引起TSA型硫酸盐破坏与水泥基材料中所用水泥的铝酸三钙含量有关。

The cement-limestone pastes and mortars mixed with different kinds and mass fractions of gypsum were immersed in water at （5±1）℃ for a long time. The appearance and compressive strength of specimens were determined, and the pastes were characterized by X-ray diffraction and infrared spectroscopy. The effect of gypsum addition on the performance of the pastes and the corresponding mechanism were investigated. The results indicate that when the mixing amount of gypsum is equal to or greater than 10%, thaumasite （TSA）-type sulfate attack occurs. When the mixing amount of gypsum is 3.5%-7.0%, TSA-type sulfate attack does not occur in the paste. It is indicated that the sulfate in cement-based materials could cause TSA-type sulfate attack, which is related to the content of 3CaO·Al2O3 in the cement.