Effect of flexural loading on degradation progress of recycled aggregate concrete subjected to sulfate attack and wetting-drying cycles

弯曲荷载对再生混凝土在硫酸盐侵蚀和干湿循环下劣化进程的影响（英文）

The degradation progress of recycled aggregate concrete(RAC) subjected to sulfate attack under wetting-drying cycles and flexural loading is studied. Three different stress ratios(0, 0.3 and 0.5) were applied in this test. The variations of relative dynamic elastic modulus Erd and water-soluble SO2-4 contents in RAC were used to evaluate degradation progress. The changes in mineral products and microstructures of interior concrete were investigated by means of X-ray diffraction(XRD), the environmental scanning electron microscope(ESEM) and X-ray computed tomography(X-CT). The results indicate that flexural loading accelerates the degradation of RAC under sulfate attack and wetting-drying cycles by expediting the transmission of SO2-4 into interior concrete. Furthermore, the accelerated effect of flexural loading is more obvious with the increase of stress ratio, that is because higher stress ratios can accelerate the extension of microcracks and generate more channels for the transmission of SO2-4. Also, more expansive products(gypsum and ettringite) are generated by the reaction of Ca(OH)2 with SO2-4, which can further accelerate the degradation of RAC.

研究了在干湿循环和弯曲荷载作用下再生混凝土硫酸盐侵蚀劣化进程.试验中使用了3种不同的荷载率(0,0. 3和0. 5),通过对再生混凝土的相对动弹性模量和水溶性SO_4^(2-)含量的变化来研究其劣化进程.并利用XRD,ESEM和X-CT等测试手段来研究再生混凝土劣化过程中内部产物与微结构的变化.结果表明,弯曲荷载能够加速再生混凝土在硫酸盐侵蚀和干湿循环下的劣化,并且加快SO_4^(2-)向混凝土内部的传输速度.这是因为随着荷载率的增加,再生混凝土的微裂纹会加速扩展,为SO_4^(2-)的传输提供更多的通道.而SO_4^(2-)将会与水化产物反应生成膨胀性产物(石膏和钙矾石),进一步加速了再生混凝土的劣化过程.