混凝土硫酸盐侵蚀影响因素的试验研究

Experimental Study on Influence Factors of Sulfate Attack of Concrete

硫酸盐侵蚀混凝土使建筑物在没有达到预期的设计使用寿命时就发生破坏,混凝土的配合比(水灰比和胶砂比)、尺寸及预养方式是否影响硫酸盐的侵蚀速度。该文以胶砂试件的抗折抗蚀系数和抗压抗蚀系数作为评定的标准,试件的制备过程按照GB/T 17671-1999,选有代表性的硫酸钠和硫酸镁溶液作为浸蚀溶液,并使溶液浓度保持其设定值,溶液每隔28 d更换一次,在规定龄期测试件强度。结果表明:试件的水灰比越大,胶砂比越小,尺寸越小(比表面积越大),侵蚀速度越快;提高预养温度、缩短预养时间可以加快侵蚀速度;硫酸镁侵蚀破坏的速度比硫酸钠侵蚀慢。对硫酸钠型侵蚀,采用抗折抗蚀系数作为判定指标较为合理,对硫酸镁型侵蚀,应该综合考虑抗折抗蚀系数和抗压抗蚀系数。

The sulfate attack of concrete would damage the useful life of buildings.Through many tests and strength analyses,the effects of concrete＇s mixture ratio,size and precured method on the rate of sulfate attack are investigated and discussed here,including sodium sulfate and magnesium sulfate attack.The results show that the speed of attack is accelerated with the increasing of the water/cement ratio and specific surface area of the specimen,as well as the decreasing of the cement/sand ratio and size of the specimen.The high precured temperature and short precured time would accelerate the speed of sulfate attack.The speed of magnesium sulfate attack is slower than that of sodium sulfate attack.It is suitable to adopt the coefficient of tensile strength as the assessing criterion of the sodium sulfate attack,and the coefficient of tensile and compressive strength should be considered together as the assessing criterion of the magnesium sulfate attack.