摘要
处于硫酸盐侵蚀环境中服役的铁路混凝土结构,混凝土内部因膨胀性物质生成导致内部开裂。实际施工混凝土养护龄期往往达不到28 d要求,早龄期阶段混凝土水泥水化不充分、内部孔隙较多,更易受到硫酸盐侵蚀,影响结构的耐久性。为探究现浇铁路混凝土结构在干湿循环和硫酸盐双重作用下的耐久性能,进行了宏观强度试验和微观SEM试验,建立硫酸盐环境下早龄期混凝土微观结构与宏观性能之间的联系。以玉磨铁路C35和C50配合比配制的试件作为研究对象,标准养护3 d和7 d后进行30,60,90,120,150,200,250和300次硫酸盐干湿循环侵蚀试验,通过比较混凝土抗压强度、抗压强度耐蚀系数、相对质量变化和微观结构,探究早龄期混凝土的抗硫酸盐侵蚀能力。研究结果表明:对于不同强度等级及养护时间的混凝土,钙矾石在其中起填充作用的时间长短不同,填充作用在C35混凝土中比在C50混凝土中长30个循环;养护时间越短,混凝土受侵蚀前期抗压强度及质量增加越多,但侵蚀后期劣化越严重,300次干湿循环后C50-3 d,C50-7 d,C35-3 d和C35-7 d抗压强度耐蚀系数分别为0.80,0.85,0.74和0.77;电子扫描显微镜(SEM)微观形貌分析展现了硫酸盐侵蚀过程中粉煤灰颗粒及钙矾石晶体的微观形状变化过程,探明了硫酸盐侵蚀产物在混凝土中由填充作用转变为膨胀开裂作用的过程。
For railway concrete structures in sulfate attack environment,the internal cracking of concrete caused by the formation of expansive substances directly affects the safety and durability of engineering structures.The curing age of concrete in actual construction often can not meet the requirements of 28 days.In the early age stage,the cement hydration of concrete is insufficient and there are many internal pores,which are more vulnerable to sulfate erosion and affect the durability of the structure.In order to explore the durability of cast-insitu railway concrete structure under the dual action of dry wet cycle and sulfate,macro strength tests and micro SEM tests were carried out to establish the relationship between microstructure and macro performance of early age concrete in sulfate environment.The test specimens prepared with the C35 and C50 mix ratio of Yumo railway were used as the research object.After standard curing for 3 d and 7 d,the specimens were subjected to 30,60,90,120,150,200,250,300 times of sulfate drying-wetting cycles erosion tests.By comparing compressive strength,compressive strength corrosion resistance coefficient,relative mass change and microstructure of the concrete,the sulfate corrosion resistance of early age concrete was explored.The results show that the filling time of ettringite in concrete with different strength grade and curing time is different,and the pore filling process by ettringite in C35 concrete extends 30 cycles longer than that of C50 concrete.The shorter the curing time is,the more compressive strength and mass of concrete increase in the early stage of erosion,while the deterioration is more intense in the later stage of erosion.After 300 drying and wetting cycles,the corrosion resistance coefficients of C50-3 d,C50-7 d,C35-3 d and C35-7 d are 0.80,0.85,0.74 and 0.77,respectively.The results of SEM test micrograph analysis show the micro shape change process of fly ash particles and ettringite crystals in the process of sulfate corrosion,and it is revealed that the process of sulfate corrosion products in concrete changes from filling to expansion cracking.
作者
徐倩
周太全
华渊
张雅婷
王英杰
XU Qian;ZHOU Taiquan;HUA Yuan;ZHANG Yating;WANG Yingjie(School of Environmental and Civil Engineering,Jiangnan University,Wuxi 214122,China;The 4th Engineering Co.,Ltd of China Railway 25th Bureau Group,Liuzhou 545007,China)
出处
《铁道科学与工程学报》
CAS
CSCD
北大核心
2022年第1期151-160,共10页
Journal of Railway Science and Engineering
基金
江苏省自然科学基金资助项目(BK20190604)
江南大学研究生科研与实践创新计划项目(JNSJ19_014)。
