碳酸盐环境对隧道混凝土性能和微观特征的影响

Influence of Carbonate Environment on Performance and Microscopic Characteristics of Tunnel Concrete

为探索喀斯特岩溶地区铁路混凝土隧道衬砌的侵蚀劣化情况,以普通硅酸盐水泥混凝土、硫铝酸盐水泥混凝土和喷射混凝土为研究对象,并模拟碳酸盐加速腐蚀环境。通过宏观性能测试和X射线衍射分析、傅里叶红外光谱分析、热重分析和扫描电子显微镜等微观测试方法,研究碳酸盐环境对不同种类隧道混凝土宏观性能和微观特征的影响。研究结果表明:混凝土的质量、相对动弹性模量和抗压强度随浸泡龄期的增长呈先增长后下降的趋势,浸泡180 d后开始下降,其中硫铝酸盐水泥混凝土浸泡360 d后的抗压强度低于初始值;侵蚀360 d后,样品原有水化产物中的晶体和凝胶数量急剧减少,并产生大量的碳酸钙;硫铝酸盐水泥混凝土样品中检测到了[Si(OH)_(6)]^(2-)八面体基团,证明有碳硫硅钙石生成,以钙矾石为主要水化产物的硫铝酸盐基混凝土受碳酸盐侵蚀影响更为明显。

To investigate the erosion and deterioration of railway tunnel lining concrete in karstic areas,this study focuses on ordinary Portland cement concrete and calcium sulfoaluminate cement concrete,as well as shotcrete.An environment of accelerated corrosion through carbonate exposure was simulated.The impact of carbonate environment on the macroscopic properties and microscopic characteristics of different types of tunnel concrete was studied using macroscopic performance testing and microscopic testing methods such as X-ray diffraction analysis,Fourier-transform infrared spectroscopy,thermogravimetric analysis and scanning electron microscopy.The mass,relative dynamic modulus of elasticity and compressive strength of concrete show an initial increase followed by a subsequent decrease with the increase of immersion duration.The decline starts after 180 d of immersion,in which the compressive strength of calcium sulfoaluminate cement concrete is lower than the initial value after immersing for 360 d.Microstructural analysis of the concrete reveals that after 360 d of erosion,the crystals and gels in the original hydration products of the samples sharply decrease,giving rise to a significant amount of calcium carbonate.In the samples of calcium sulfoaluminate cement concrete,[Si(OH)_(6)]^(2-)octahedral groups are detected,confirming the formation of thaumasite.The calcium sufoaluminate cement-based concrete with ettringite as the main hydration product is more significantly affected by carbonate erosion.