硫酸盐侵蚀与冻融循环共同作用下混凝土损伤研究

Study on Damage of Concrete under the Combined Action of Sulfate Attack and Freeze-thaw Cycle

对水胶比为0.45的引气混凝土分别在质量分数为1%Na2SO4、5%Na2SO4、5%MgSO4溶液及水中进行快速冻融试验,采用超声平测法测量混凝土损伤层厚度,分析了不同溶液中混凝土的损伤层、未损伤层超声波速及损伤层厚度随冻融循环次数的变化规律。结果表明:混凝土损伤层厚度能够反映硫酸盐-冻融共同作用下混凝土损伤程度;不同溶液与冻融共同作用下混凝土损伤程度有所不同,原因在于硫酸盐溶液对混凝土冻融破坏既存在抑制作用,又存在促进作用;随着硫酸钠溶液浓度的升高,硫酸钠溶液对混凝土的冻融破坏由促进作用逐渐转变为抑制作用,由于硫酸镁具有镁盐和硫酸盐的双重腐蚀,对混凝土的冻融破坏促进作用最大。

It was studied air-entraining concrete with the water-binder ratio of 0. 45 under rapid freezing and thawing test in solutions of 1% Na2SO4、5% Na2SO4、5% MgSO4 and water. Using the ultrasonic detector tested the thickness of damaged layer, analyzing the ultrasonic wave velocity of the undamaged layer,damaged layer and the thickness of the damaged cycles. The results show that the thickness of layer in the concrete changing with the freeze-thaw damaged layer in concrete can reflect its damaged degree under the combined action of sulfate and freeze-thaw. The damaged degree of the concrete is different under the action of different solution and freeze-thaw cycles, because the sulfate solutions have both inhibitory effect and promoting effect on the freeze-thaw damage of the concrete. With the increase of solution concentration, the promoting effect of freeze-thaw damage for the concrete with sulfate solution change to be inhibitory effect. Because of the magnesium sulfate has dual corrosion of magnesium salt and sulfate, the promoting effect on the freeze-thaw damage of concrete is largest.