基于工业扫描分析混凝土气泡结构与抗盐冻性能

Application of Industrial Computerized Tomography to Analyze Air Voids Structure and Salt Scaling Resistance of Concrete

利用工业扫描(CT)技术对混凝土盐冻过程中气泡结构变化进行可视化表征和定量计算.研究发现引气是提高混凝土抗盐冻性能最重要的手段,建议含气量为5%~7%,同时气泡间距系数与混凝土抗盐冻性能有直接关系,气泡间距系数小于238μm时混凝土具有较好的抗盐冻性能.引气混凝土由于内部有大量小而封闭的气泡,其气泡间距系数较小,盐冻过程中气泡能够缓解结冰压,降低盐冻破坏的程度;非引气混凝土由于结冰压无法释放,当结冰压大于混凝土所能承受的膨胀力时,会在表面产生微裂缝并逐渐扩展,最终造成表面浆体剥落,形成盐冻破坏.

This paper utilizes the industrial computerized tomography to visualize and to calculate the microstructure change of concrete during cyclic freeze-thaw test. The results indicate that entraining air is the sufficient way for improving the frost resistance of concrete, and the suggested air content is 5% -7%. Also, the air void space directly affects the frost resistance of concrete, and concrete can well resist frost damage when the air void space is shorter than 238 μm. The air-entrained concrete has significant amount of fine air voids with shortened air void space, and the fine air voids can release the ice forming pressure during freezing, thus protecting the concrete from frost damage. The ice forming pressure can barely release for non-air entrained concrete,and micro-cracks forms when the ice forming pressure exceeded the allowable stress of concrete, and finally results in material loss or frost damage.