冻融与盐蚀耦合作用下混凝土的细观特征与损伤演化规律  

Mesoscopic Characteristics and Damage Evolution of Concrete Under Coupling Freeze-Thaw and Salt Erosion

作　　者：陈少杰[1] 任建喜[1] 刘浪[2] 李玉根 任翔[1] 符强 CHEN Shaojie;REN Jianxi;LIU Lang;LI Yugen;REN Xiang;FU Qiang(School of Architecture and Civil Engineering,Xi'an University of Science and Technology,Xi'an 710054,China;School of Energy Engineering,Xi'an University of Science and Technology,Xi'an 710054,China;School of Architecture Engineering,Yulin University,Yulin 719000,Shaanxi,China;Shanxi Modern Architectural Design and Research Institute Co.,Ltd,Xi'an 710021,China)

机构地区：[1]西安科技大学建筑与土木工程学院,西安710054 [2]西安科技大学能源学院,西安710054 [3]榆林学院建筑工程学院,陕西榆林719000 [4]陕西省现代建筑设计研究院有限公司,西安710021

出　　处：《硅酸盐学报》2024年第11期3524-3536,共13页Journal of The Chinese Ceramic Society

基　　金：国家自然科学基金(52268047);陕西省自然科学基础研究计划(2024JC-YBQN-0610);陕西省博士后科研项目(2023BSHEDZZ310);陕西省“四主体一联合”地下结构抗震校企联合研究中心开放基金(KY2024-YB01);榆林市科技计划项目(CXY-2022-157)。

摘　　要：通过快速冻融试验,结合X射线计算机断层成像(CT)扫描技术和三维重构分析,在细观尺度上研究了不同氯盐浓度环境与冻融作用下混凝土剥落深度、体积损失率、孔隙结构和CT值的变化规律。基于CT数据建立了混凝土的损伤演化模型,并与波幅和质量定义的损伤进行了对比分析。结果表明:冻融与盐蚀耦合作用下混凝土主要发生砂浆剥落破坏,剥落深度和体积损失率随冻融次数的增加而增大。冻融过程中混凝土的损伤由表及里,随着表面砂浆剥落,部分闭口孔逐渐转为开口孔,最终消失,试样孔隙率整体呈波动增大趋势。氯盐浓度对混凝土冻融损伤发展速度影响显著,随着氯盐浓度的增加,混凝土的剥落深度和体积损失率呈先增大后减小的趋势。混凝土的超声波波幅随冻融次数的增加逐渐减小,二者存在较好的指数关系。试验设计的4种浓度中,3.5%(质量分数)氯盐溶液中的混凝土冻融破坏最严重。基于CT数据定义的损伤演化模型与波幅和质量表征的损伤度线性关系良好,且与质量损失率吻合度更高,说明该模型较好地反映了混凝土的损伤演化过程。Introduction Concrete structures serving in cold regions are often affected by freeze-thaw damage,which is the main reason for the loss of durability in cold region concrete.Additionally,cold region concrete is also subject to salt erosion due to factors such as soil salinity and winter salt application.The coupled action of freeze-thaw and salt attack causes more severe damage to the internal structure of concrete materials,greatly impacting their service life.The deterioration of concrete durability under the coupled action of freeze-thaw and salt attack is primarily manifested as degradation of macroscopic properties such as mass,dynamic elastic modulus,and strength,accompanied by changes in the microstructure.The deterioration process is a complex physical-chemical process involving multiple scales.Merely focusing on the evolution of macroscopic properties often hinders a deep understanding of the degradation mechanisms.Therefore,it is of great significance to clarify the evolution process of microscopic features of concrete under the coupled action of freeze-thaw and salt attack,quantitatively characterize the damage evolution laws from the perspective of pore structure,spalling depth,and compactness,in order to gain a profound understanding of the coupling mechanism and degradation mechanisms of both phenomena.Methods Concrete specimens were prepared using volume-stable P·O 42.5 ordinary Portland cement,river sand with a fineness modulus of 2.5,and coarse aggregates ranging from 5 mm to 10 mm.The dimensions of the concrete specimens were 100 mm×100 mm×100 mm.NaCl solutions with four different concentrations,namely 0%,3.5%,5.0%,and 8.0%,were used as the corrosive medium in the freeze-thaw process.A freeze-thaw cycling tests according to the fast freezing method specified in GB/T50082—2009.Concrete specimens were scanned using a LightSpeed 64-layer helical CT scanner with a resolution of 512×512 pixels and an X-ray tube voltage of 120 kV.To prevent water evaporation and loss of moisture during CT scanni

关 键 词：冻融 盐蚀 混凝土 细观特征 扫描技术 损伤分析 

分 类 号：TU528[建筑科学—建筑技术科学]