酸雨侵蚀下水泥石物相组成变化的微观分析(英文)

MICROANALYSIS OF THE CHANGE OF PHASE COMPOSITIONS OF HARDENED CEMENT PASTE IN RESPONSE TO ACID RAIN ATTACK

用X射线衍射、Fourier变换红外光谱、扫描电子显微镜和X射线能量色散谱等方法研究了浸泡在pH值为2的模拟酸雨中硅酸盐水泥石物相组成的变化。结果表明:硬化水泥浆体的破坏主要是酸雨中H+与SO42-共同作用的结果。一方面,H+使硬化水泥石中的Ca(OH)2,水化硅酸钙(C-S-H)凝胶,xCaO.Al2O3.yH2O(CxAHy)等物质发生分解、转化,而引起结构溃散性腐蚀;另一方面,SO24-与水泥石作用,生成膨胀性的物质CaSO4.2H2O,而引起膨胀性腐蚀。在酸雨持续作用下,水泥石由表及里逐渐遭到侵蚀破坏,直至完全溃散,最终转变成由石膏、硅胶和铝胶等组成的一种白色稀泥状混合物。

The change of phase compositions of hardened ordinary Portland cement paste exposed to simulated acid rain was analyzed by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray diffraction analysis. The pH value of the simulated acid rain, containing SO4^2-, NO3^-, NH4^＋ and Mg^2＋, was 2. The results show that under the sustaining action of acid rain, normal cement hydrated products, such as Ca（OH）2, hydrated calcium silicate （C-S-H） gel, xCaO. Al2O3·yH2O（CxAHy） and ettringite are decomposed gradually and transformed into a white mushy mixture consisting of CaSO4·2H2O crystal, SiO2·nH2O gel and Al2O3·nH2O gel. The destruction of the cement matrix by acid rain attack is predominantly due to the coordinated effect of the dissolving erosion by H^＋ and the expanding erosion by SO4^2-, and occurs from the surface to the interior of materials.