硫酸盐侵蚀-干湿循环下不锈钢纤维再生混凝土耐久性分析

Durability analysis of stainless steel fiber recycled concrete under sulfate-dry-wet cycle

由于我国黄河流域盐渍土地区含有高浓度SO_(4)^(2-),影响着在役混凝土的力学性能和耐久性,严重阻碍了再生混凝土(RAC)在工程中的应用。【目的】为快速研究黄河流域盐渍土地层含有高浓度SO_(4)^(2-)并伴随地下水入渗和蒸发的侵蚀特点,【方法】以304不锈钢纤维再生混凝土(304SSFRAC)为研究对象,以再生混凝土(RAC)和普通钢纤维再生混凝土(PFRAC)作对比,采用5%Na_(2)SO_(4)作为侵蚀溶液,开展硫酸盐侵蚀-干湿循环作用的室内耐久性快速试验,研究立方体抗压强度、相对动弹性模量和相对质量,并通过扫描电子显微镜(SEM)手段来表征304SSFRAC微观结构,最后采用Weibull函数建立耐久性退化模型来预测试件寿命。【结果】结果显示:在0~75次的循环周期内,试件立方体抗压强度、质量和动弹性模量有明显的增强,在75次循环后,试件表面出现微裂纹,各项性能指标开始下降;SEM微观观察到混凝土内部腐蚀产物包括钙矾石、石膏等晶体。通过Weibull函数建模可得到试件寿命,【结论】结果表明,试件寿命为304SSFRAC>PFRAC>RAC,体积掺量为2%的304SSFRAC在5%Na_(2)SO_(4)干湿循环下最长使用寿命可达到499次左右。

[Objective]Due to the saline soil area of the Yellow River Basin in my country contains high concentrations of SO_(4)^(2-),which affects the mechanical properties and durability of in-service concrete,and seriously hinders the application of recycled concrete(RAC)in engineering.[Methods]Based on the erosion characteristics of high concentration of SO_(4)^(2-)in saline soil and groundwater infiltration and evaporation in the Yellow River Basin,this paper takes 304 stainless steel fiber recycled concrete(304SSFRAC)as the research object,compares RAC with ordinary steel fiber recycled concrete(PFRAC),and uses 5%Na_(2)SO_(4) as the erosion solution to carry out the indoor durability accelerated test of sulfate erosion-wet-dry cycle.The compressive strength,relative dynamic elastic modulus and relative mass of the cube were studied,and the microstructure of 304SSFRAC was characterized by scanning electron microscope(SEM).Finally,the durability degradation model was established by Weibull function to predict the life of the specimen.[Results]The result show that the cubic compressive strength,mass and dynamic elastic modulus of the specimen are obviously enhanced in the cycle from 0 to 75 times,and after 75 cycles,the surface of the specimen appears microcracks,and all performance indexes begin to decline.Microscopically,the corrosion products in concrete include ettringite,gypsum and other crystals.Through Weibull function modeling,[Conclusion]The result show that test piece life 304SSFRAC>PFRAC>RAC,and the maximum service life of 304SSFRAC with 2%volume content can reach about 499 times under 5%Na_(2)SO_(4) dry-wet cycle.