5～40℃不同硫酸盐侵蚀对铝酸盐水泥水化的影响

Effect of Sulfate Attack on Hydration of Calcium Aluminate Cement at 5-40 ℃

采用X射线衍射仪、热分析仪、压汞仪等分别研究了5℃、20℃和40℃Na2SO4和MgSO4侵蚀对铝酸盐水泥(CAC)水化的影响。结果表明:不同温度CAC水化产物的稳定性与硫酸盐种类密切相关。在5℃和20℃,浆体中主要生成十水铝酸钙(CAH10)和八水铝酸二钙(C2AH8),两者在MgSO4溶液侵蚀下均能稳定存在;但在Na2SO4溶液侵蚀下,C2AH8不稳定而基本消失,并有膨胀性钙矾石形成,试样强度降低。在40℃,浆体中主要生成C2AH8和六水铝酸三钙(C3AH6),其中C3AH6在Na2SO4溶液侵蚀下基本稳定,而C2AH8在两种硫酸盐溶液侵蚀下均基本消失,Na2SO4侵蚀样中形成大量钙矾石,MgSO4侵蚀样中则形成大量石膏,试样破坏严重。但在40℃高温条件下,两种硫酸盐侵蚀均可在一定程度上起到收缩补偿作用。

The effect of Na2 SO4 and MgSO4 attack on the hydration of calcium aluminate cement(CAC) at different temperatures(i.e., 5, 20 and 40 °C) was investigated by X-ray diffraction, thermal analyzer and mercury intrusion porosimetry. The results show that the stability of CAC hydration products at different temperatures is closely related to the types of sulfate. At 5 °C and 20 °C, CaO·Al2O3·10 H2 O(CAH10) and 2 CaO·Al2O3·8 H2 O(C2AH8) are mainly formed in the paste, both of them can exist stably under the attack of MgSO4 solution. However, C2AH8 is unstable and disappears under the attack of Na2 SO4 solution and expanded ettringite is formed, resulting in the decrease of strength. At 40 °C, C2AH8 and 3 CaO·Al2O3·6 H2 O(C3AH6) are mainly formed in the paste. For C3AH6, it can only be stable under the attack of Na2 SO4 solution, but C2AH8 disappears under the attack of both sulfate solutions, and massive ettringite and gypsum are formed in Na2 SO4 and MgSO4 attacked samples, respectively, leading to severe damage to the samples. However, at 40 °C, the two types of sulfate attack can compensate shrinkage to some extent.