冻融环境下黏土红砖的性能劣化规律与微结构演化

Performance deterioration and microstructure evolution of clay brick submitted to freeze-thaw cycles

系统研究了黏土红砖在冻融环境下的外观、质量损失率及相对动弹模量变化；采用压汞法分析了黏土红砖冻融前后的孔径分布变化规律，并应用X射线计算机断层扫描技术原位定量追踪了黏土红砖冻融环境下的三维孔结构演化过程．结果表明，冻融初期黏土红砖外观破坏不明显，35次冻融循环后开始出现宏观裂纹，65次冻融循环后分层，并沿分层界面剥落．黏土红砖质量及相对动弹模量随冻融次数的增加均表现出先略有增大再下降的规律，并且质量变化敏感．孔结构分析结果表明，65次冻融循环后黏土红砖平均孔径增大近4倍，气孔总体积增加23％，体积为0．01～0．1 mm^3的气孔数量和体积显著增多，抗冻性能明显降低．

The changes of appearance,mass loss percentage and relative dynamic elastic modulus of clay brick submitted to freeze-thaw cycles were systematically studied.The mercury intrusion poro-simetry （MIP）was utilized to investigate the pore size distribution before and after freeze-thaw cy-cles.The X-ray computed tomography （CT）was also used to in situ quantitatively observe the evo-lution of the three-dimensional pore structure under freeze-thaw cycles.The results show that the frost damage is slight in the early stages.Macroscopic cracks appear on the surface after 35 freeze-thaw cycles and spalling occurs after 65 cycles.Mass is more sensitive when submitted to freeze-thaw cycles and shows a similar regulation as the relative dynamic elastic modulus with a first gradual increase,followed by a decrease.The pore structure analysis results show that the average pore size increases about 4 times after freeze-thaw cycles with coarse pores increasing by 23% in volume. Simultaneously,the number and the volume of pores with the volume of 0.01 to 0.1 mm3 increase evidently.The frost resistance of clay red brick is reduced consequently.