含石膏质岩集料的混凝土内部硫酸盐侵蚀及抑制措施

Internal Sulphate Attack and Corresponding Control Measures of Concrete with Gypseous Rocks as Aggregate

集料中掺杂过量的硫酸盐尤其是石膏会引起混凝土内部硫酸盐侵蚀膨胀,破坏混凝土结构。研究了集料中掺杂石膏的含量、粒径对砂浆试件强度和膨胀率的影响,探讨了水泥C3A含量、矿物掺合料品种对含石膏质岩集料混凝土内部硫酸盐侵蚀的抑制效果。结果表明:随着集料中掺杂石膏质岩细粉含量的增大,内部硫酸盐侵蚀反应的速率和程度增大,当掺杂SO3含量超过1.25%时,12个月龄期的砂浆膨胀率超过0.1%并出现较大的强度损失;掺杂石膏质岩粒径越小,砂浆的膨胀率和强度损失一般越大,特别是当掺杂石膏质岩粒度小于1.18mm后将引起显著的膨胀,而当粒径大于4.75mm后,由于石膏质岩集料在混凝土中分散的不均性而产生不均匀体积膨胀,从而导致侵蚀应力集中,即使较低的SO3含量掺杂石膏质岩也有可能产生较大的强度损失。采用抗硫酸盐硅酸盐水泥及掺加适量的粉煤灰、硅灰或偏高岭土等矿物掺合料,可以有效抑制含石膏质岩集料混凝土的内部硫酸盐侵蚀膨胀。

It may lead the internal sulphate attack in concrete if aggregates mixing excessive sulfate especially gypsum and damage the concrete structure. The effect of the gypsum content, grain size on the strength and expansion ratio of concrete and mortar are studied and discussed in this paper. Some measures are proposed for inhibiting the internal sulfate attack in concrete. The results show that with the increasing of SO3 content the attack rate become bigger if gypseous rocks as fine powder in concrete. The significant expansions （〉0.1%） and big losses of strength would occur if the SO3 content exceed 1.25% after water curing 1 year. The rate of internal sulfate attack will be bigger as the decreasing particle size of fine aggregates in concrete. It would lead significant expansions if the particle size less than 1.18 mm of gypseous rocks as fine aggregate. It would lead to stress concentration due to uneven distribution of the gypseous rocks aggregate size over 4. 75mm, even if the low SO3 content in mixed gypsum rocks may induce big strength loss. It inhibits internal sulfate attack effective in addition of appropriate amount of meta kaolin, fly ash, silicate fume and use sulfate resistant cement.