盐–冻融/干湿循环作用下纤维混凝土耐久性能  

Durability of Fiber Reinforced Concrete Under Salt-Freeze-Thaw/Dry-Wet Cycles

作　　者：段明翰 覃源[1] 李阳[1] DUAN Minghan;QIN Yuan;LI Yang(State Key Laboratory of Eco-hydraulics in Northwest Arid Region,Xi'an University of Technology,Xi'an 710048,China)

机构地区：[1]西安理工大学省部共建西北旱区生态水利国家重点实验室,西安710048

出　　处：《硅酸盐学报》2024年第12期3703-3717,共15页Journal of The Chinese Ceramic Society

基　　金：国家自然科学基金面上项目(52279139)。

摘　　要：为探究纤维混凝土在高寒盐渍土环境下的耐久性能,对西藏地区某工程现场暴露养护后的聚丙烯、聚丙烯腈及聚酯等3种纤维混凝土进行复合盐–冻融/干湿循环加速试验,通过测试试件超声波波速、劈拉强度及微观结构,进一步分析耐久性能衰减规律及损伤机理。结果表明:现场暴露养护下纤维混凝土均出现网状结构微裂纹,与素混凝土有显著差异;而表面裂纹与内部裂缝在盐–冻融/干湿循环作用下逐渐联通则会造成波速和劈拉强度下降;纤维的桥联–阻裂–增韧作用以能量传递方式体现,通过改善界面过渡区处的裂纹扩展能力,延缓了劈拉过程中的荷载损伤;波速损伤量与劈拉强度具有显著的相关性,建立的预测模型在一定程度上具有适用性。Introduction In alpine saline soil environments,concrete has a multi-factor coupling degradation due to the freeze-thaw cycles,as well as sulfate and chloride corrosion.This degradation results in a significant decline in structural lifespan primarily due to reduced material durability.The maintenance process is complex and incurs substantial economic losses,attracting considerable attentions.Under the influence of these coupled factors,the presence of salt facilitates the migration of water toward the salt.Upon reaching the critical freezing point,ice jams occur,leading to concrete damage from ice pressure.Also,the formation of numerous expansion products generates an expansion pressure during dry-wet cycles,further contributing to concrete deterioration.Although the use of fiber-reinforced concrete has a potential to mitigate these issues,tight construction timelines can result in an initial damage,such as cracks during winter construction,which are often unavoidable.The existing research on the durability and mechanisms of fiber-reinforced concrete in real crack states within this environment remains insufficient,indicating a need for a further research.Methods This study examined the fiber-reinforced concrete used in a project located in the alpine saline soil region of Tibet,China.Three distinct types of fiber concrete specimens were designed and manufactured with polypropylene fiber(PPF),polyacrylonitrile fiber(PANF),and modified polyester fiber(PEF).After 150 d outdoor curing,the actual cracks were analyzed by a microscope.Two accelerated degradation tests were conducted,i.e.,composite salt-freeze-thaw and composite salt–dry–wet cycles.The durability damage mechanisms and patterns were investigated in detail through measurements of ultrasonic wave velocity and splitting tensile strength,as well as by scanning electron microscopy.Results and discussion According to the crack information statistics of the specimens after outdoor exposure and curing,the cracks in plain concrete are straight and singular,w

关 键 词：纤维混凝土 高寒盐渍土 冻融/干湿循环 超声波波速 劈拉强度 预测模型 

分 类 号：TV431.3[水利工程—水工结构工程]