硅酸盐学报2025，Vol.53Issue(5)：1236-1246,11.DOI:10.14062/j.issn.0454-5648.20240714
裂后超高性能混凝土在冻融循环下拉伸性能演化
Tensile Performance Evolution of Cracked Ultra-High-Performance Concrete Under Freeze-Thaw Conditions
摘要
Abstract
Introduction Ultra-High Performance Concrete(UHPC)is widely recognized for its exceptional mechanical properties and durability,making it a cornerstone material in modern infrastructure projects.However,the long-term service performance of UHPC structures with initial cracks under freeze-thaw(F-T)cycling remains a safety concern,particularly in harsh environments such as cold regions and coastal zones.While extensive research has focused on the properties of uncracked UHPC,the study on degradation of cracked UHPC under coupled F-T cycling and self-healing conditions is limited.Existing studies highlight UHPC's intrinsic self-healing potential through secondary hydration and carbonation reactions,yet the interplay between these healing mechanisms and cyclic F-T-induced deterioration remains unclear.To address this,the present study investigates the tensile performance evolution of pre-cracked UHPC under F-T cycling and water-curing conditions.By integrating macroscopic mechanical tests with microscopic analyses,this work aims to unravel the dual effects of self-healing and F-T-induced damage on UHPC's structural integrity. Methods UHPC specimens were prepared using white cement,silica fume,quartz powder/sand,steel fibers(2%by volume),and a polycarboxylate superplasticizer.The mix design followed a water-to-binder ratio of 0.22.After casting and demolding,specimens underwent 48 h hot-water curing at 90℃.Dog-bone-shaped specimens(30 mm×13 mm×80 mm)were pre-notched and subjected to pre-tensioning to introduce controlled initial cracks(100 μm width)via displacement-controlled loading.Pre-cracked specimens were divided into two groups,including 1)F-T cycling groups:Exposed to 100,200,or 300 F-T cycles(-17℃to 8℃per cycle);2)water-curing groups:immersed in 20℃water for 14,30 d,or 60 d.Secondary tensile tests were conducted to evaluate residual strength and crack recovery.Single-fiber pull-out tests assessed interfacial bond performance,while scanning electron microscopy(SEM)and thermogravimetric analysis(TGA)characterized microstructural evolution and hydration products. Results and discussion Water-cured specimens exhibited remarkable mechanical recovery.After 60 d,tensile strength exceeded the undamaged control group by 32%,attributed to C-S-H gel and Ca(OH)2 filling microcracks.SEM revealed dense microstructures with nearly closed cracks,confirming the role of secondary hydration in enhancing matrix integrity.Single-fiber pull-out tests showed interfacial bond strength fully recovered within 30 d,though prolonged immersion led to steel fiber corrosion,reducing post-peak ductility.F-T cycling initially promoted low-temperature self-healing.After 200 cycles,tensile strength increased by 14%due to partial crack closure via hydration.However,beyond 300 cycles,cumulative damage dominated:surface spalling,fiber corrosion,and interfacial debonding caused a 7.1%decline in tensile strength.TGA confirmed reduced Ca(OH)2 and CaCO3 content under F-T conditions,indicating suppressed hydration and carbonation compared to water curing.Progressive densification of the matrix with crystalline hydration products sealing cracks.Initial healing at 100-200 F-T cycles was counteracted by interfacial microcrack propagation and fiber-matrix debonding at 300 cycles.EDS analysis highlighted localized CaCO3 precipitation at crack surfaces,insufficient to offset F-T-induced damage.The study revealed a critical threshold(200 F-T cycles)where self-healing and deterioration mechanisms compete.While water ingress facilitates secondary hydration,prolonged F-T exposure disrupts the healing process through ice crystallization pressure and moisture redistribution,exacerbating matrix degradation. Conclusions Water curing significantly enhances UHPC's self-healing capacity,with complete tensile strength recovery,which was driven by continuous secondary hydration and carbonation,forming dense,crack-resistant matrices.Freeze-thaw cycling exhibited a dual role:healing occurred at early stages(≤200 cycles),but 300 cycles led to irreversible strength loss.Microstructural analysis underscored the importance of hydration products(C-S-H,CaCO3)in healing cracks,while F-T cycling disrupts interfacial bonding and accelerates matrix spalling.For UHPC structures in cold climates,proactive crack sealing and controlled curing are essential to maximize self-healing benefits before F-T damage accumulates.Future work should explore hybrid curing regimes and corrosion-resistant fibers to extend service life.关键词
超高性能混凝土/自愈合/冻融循环/拉伸性能Key words
ultra-high performance concrete/self-healing/freeze-thaw cycles/tensile performance分类
建筑与水利引用本文复制引用
林勋,赵梦佳,陈璨,张洪锐,钟锐,王景全,姚一鸣..裂后超高性能混凝土在冻融循环下拉伸性能演化[J].硅酸盐学报,2025,53(5):1236-1246,11.基金项目
国家自然科学基金(52278245) （52278245）
中央高校基本科研业务费(2242023R40006). （2242023R40006）
