硫酸盐侵蚀下混凝土单轴压缩力学行为模拟及孔隙特征研究

为了研究硫酸盐侵蚀下混凝土力学行为及内部孔隙结构的变化规律,本文对在0%、10%、15%、20%四种不同质量分数硫酸钠溶液浸泡210 d的混凝土试件进行单轴压缩试验,并通过PFC^2D软件模拟应力场分布以研究试验过程中裂缝演化规律,并结合核磁共振分析其浸泡后内部孔隙分布情况。结果表明:混凝土的峰值应力、弹性模量均随浸泡浓度的增大而下降;根据PFC^2D模拟结果,在单轴压缩过程中混凝土内部最早出现张拉裂缝,随后裂缝继续扩展,逐渐出现张拉与剪切复合裂缝,最终形成一条沿对角线贯穿的剪切裂缝;硫酸盐侵蚀后混凝土T₂分布曲线有3个波峰,内部孔隙主要以微孔、小孔为主,随着浸泡浓度的增长,其微孔逐渐向小孔转化,导致混凝土的T₂峰1幅值和面积逐渐增大。

Pore Characteristics and Simulation of Mechanical Behavior of Concrete under Uniaxial Compression with Sulfate Attack

In order to study the variation of mechanical behavior and internal pore structure of concrete under sulfate attack, uniaxial compression tests were carried out on concrete specimens soaked in 0%, 10%, 15% and 20% (mass fraction) sodium sulfate solution for 210 d. The stress field distribution was simulated by PFC^2D software to study the crack evolution during the test, and the internal pore distribution was analyzed by nuclear magnetic resonance. The test results show that the peak stress and elastic modulus of the concrete decrease with the increase of immersion concentration. According to the PFC^2D simulation results, tensile cracks first appear in the concrete during uniaxial compression, then the cracks continue to expand, and tensile and shear composite cracks appear, finally a shear crack runs through the diagonal. The T₂ distribution curve of concrete after sulfate attack shows three peaks, and the internal pores are mainly micro pores and small pores. With the increase of immersion concentration, the micro pores gradually transform into small pores, resulting in the increase of T₂ peak 1 amplitude and area of the concrete.