硫酸盐侵蚀作用下纳米混凝土力学特性及微观结构劣化机制研究

Study on Mechanical Properties and Microstructure Deterioration Mechanism of Nano⁃concrete under Sulfate Attack

硫酸盐侵蚀一直是影响混凝土耐久性的重要因素之一,特别是在西北寒旱及沿海盐渍土区。基于试验研究了硫酸盐侵蚀作用下,掺纳米SiO_(2)和纳米CuO混凝土的抗压强度、轴向应力-应变以及微观特性,并分析了硫酸盐侵蚀环境下纳米材料的改性效果。试验结果表明:随着纳米CuO掺量的提高,混凝土的抗压强度、剩余强度系数逐渐降低;当纳米SiO_(2)掺量增加时,混凝土的抗压强度、剩余强度系数先降低后升高。相比于未掺加纳米材料混凝土,掺入纳米材料能显著提高混凝土的延性。同时,对于提高混凝土的抗压强度纳米材料具有最佳掺入量,纳米SiO_(2)和纳米CuO的最佳掺量分别为3%和1%(质量分数)。此外,纳米材料具有桥接和填充效应,能抑制混凝土裂缝的发展、细化孔隙结构、提高密实度,进而提高混凝土的力学性能。

Sulfate attack has always been an important factor affecting the durability of concrete,espe-cially in the northwest cold and arid regions,and coastal saline soil area of China.Based on experi-ments,the compressive strength,axial stress-strain and microstructure properties of concrete modi-fied with nano-SiO_(2) and nano-CuO under the influence of sulfate attack were studied,and the strength-ened effect of nano-materials was analyzed.The results show that with the increase of nano-CuO con-tent,the compressive strength and residual strength coefficient of concrete gradually decreased.When the content of nano-SiO_(2) increases,the compressive strength and residual strength coefficient first de-crease and then increase.Compared with the concrete without adding nano-materials,the addition of nano-materials can improve the ductility of concrete.With the increase of erosion time,the ductility of nano-concrete is better.Meanwhile,there is an optimum content of nano-materials for improving the compressive strength of concrete,and the optimum contents of nano-SiO_(2) and nano-CuO are 3%and 1%(quality score),respectively.Additionally,nano-materials have a certain bridging and filling ef-fect,which might affect the degree of crack propagation,refine the pore structure and improve the compactness of nano-concretes,thereby improving the mechanical properties of concrete.