冻融与硫酸盐作用下再生混凝土性能劣化研究

Study on performance deterioration of recycled concrete under coupling effect of freeze-thaw and sulfate

主要研究在冻融循环和硫酸盐腐蚀共同作用下再生混凝土的力学性能以及性能劣化规律.试验采用0.35、0.45、0.55三组水灰比,再生骨料质量取代率30%,Na_(2)SO_(4)溶液浓度为5%,混凝土试块在不同冻融循环次数下,其质量、相对动弹性模量、抗压强度进行测试,并结合电镜扫描和XRD衍射实验.试验结果表明:水灰比越大,再生混凝土在冻融与硫酸盐环境下的力学性能越差,耐久性能劣化也越严重,并结合电镜扫描的图片和衍射图分析了再生混凝土的损伤.同时,以相对动弹性模量作为损伤值对再生混凝土在冻融和硫酸盐共同作用下的寿命进行了预测;结果表明:水灰比是影响其寿命的重要因素,在冻融与硫酸盐共同作用的环境下,建议再生混凝土的水灰比宜控制在0.45及以下.

This paper mainly studies the mechanical properties and performance degradation of recycled concrete under the combined action of freeze-thaw cycle and sulfate corrosion.Three groups of water-cement ratios of 0.35,0.45 and 0.55 were used in the test.The replacement rate of recycled aggregate was 30%,and the concentration of Na_(2)SO_(4) solution was 5%.The mass,relative dynamic elastic modulus and compressive strength of concrete specimens were tested under different freeze-thaw cycles,combined with electron microscopy and XRD diffraction experiments.The test results show that the greater the water-cement ratio,the worse the mechanical properties of recycled concrete under freeze-thaw and sulfate environment,and the more serious the deterioration of durability.The damage of recycled concrete is analyzed by combining the images and diffraction patterns of electron microscope scanning.At the same time,the relative dynamic elastic modulus is used as the damage value to predict the life of recycled concrete under the combined action of freeze-thaw and sulfate.The results show that the water-cement ratio is an important factor affecting its service life.Under the combined action of freeze-thaw and sulfate,it is suggested that the water-cement ratio of recycled concrete should be controlled at 0.45 and below.