硫酸盐侵蚀下水泥砂浆应力应变曲线及性能劣化研究

Stress-strain Curve and Property Deterioration of Cement Mortar under Sulfate Attack

为分析硫酸盐侵蚀引起的混凝土弹性模量、抗压强度等力学性能劣化规律,开展硫酸盐侵蚀下水泥砂浆应力应变关系的试验研究。首先,采用增设高强度弹簧钢的方法,研制了一种经济实用的测试装置,调查硫酸盐腐蚀砂浆试件的应力-应变全曲线及其时变力学性能;然后,结合其微结构形貌及孔隙率的演变,分析硫酸盐侵蚀下水泥砂浆性能的劣化原因。最后,利用最小二乘法对力学性能的试验数据进行拟合,以硫酸盐溶液浓度与浸泡时间为变量,确定水泥砂浆化学损伤程度的数学表达式。研究结果表明:硫酸盐侵蚀不会改变水泥砂浆应力-应变曲线的形状,但会导致其力学性能退化;而数学拟合公式可定量分析浸泡于不同浓度硫酸盐溶液中的水泥砂浆力学性能的时变劣化程度。

To analyze the degradation of mechanical properties like elastic modulus and compressive strength of concrete caused by external sulfate attack(ESA),an experimental study on the stress-strain relation of cement mortar under ESA was made.First,an economical and practical test device was designed by adding high strength spring steel to investigate the stress-strain curve and time-varying mechanical properties of sulfate-corroded cement mortar specimen(CMS).Then,combined with the evolution of microstructure and porosity of CMS,the reason for its performance deterioration caused by ESA was analyzed.Finally,the least square method was used to fit the experimental data of mechanical properties.Taking the concentration of sulfate solution and immersion time as variables,the mathematical expression for chemical damage of CMS was determined.The results show that ESA does not change the shape of stress-strain curve of CMS,but causes the degradation of its mechanical properties.The mathematical fitting formula can quantitatively analyze the time-varying damage degree of mechanical properties of CMS exposed to sulfate solution with different concentrations.