冻融与牛尿侵蚀共同作用下混凝土损伤研究

Study on Concrete Damage under the Combined Actions of Freeze-thaw and Cattle Urine Erosion

本文以牛尿作为侵蚀介质,研究了3种配合比混凝土冻融循环后的动弹模量和质量变化,结合XRD分析冻融与牛尿侵蚀共同破坏后的混凝土物相组成。结果表明:相较于水介质冻融循环,冻融与牛尿侵蚀共同作用下的混凝土动弹模量和质量损失明显增加,XRD衍射图谱中出现明显的碳酸钙晶体。冻融与牛尿侵蚀共同作用下的混凝土不仅受到水结冰以及尿液中无机盐和尿素结晶膨胀压的疲劳作用,牛尿也会与混凝土水化产物发生化学作用,加剧混凝土碳化腐蚀、开裂破坏。提高混凝土致密性,改善孔结构,可以减少腐蚀介质对混凝土内部的渗透,从而大幅提高混凝土在牛尿侵蚀下的抗冻耐久性。

The cattle urine was used as erosion medium,and the dynamic modulus and mass changes of concrete with three different proportions after freeze-thaw cycle were studied.The composition of concrete destroyed by the freeze-thaw and cattle urine was analyzed by XRD.The results show that compared with the freeze-thaw cycle of water medium,the dynamic modulus and mass loss of concrete under the combined actions of freezethaw and cattle urine erosion increased obviously.Moreover,obvious calcium carbonate crystals appeared in the XRD diffraction pattern.Concrete under the combined actions of freeze-thaw and cattle urine erosion is not only subjected to the fatigue function caused by water freezing and crystallization expansion pressure of inorganic salt and urea in urine,but also urine would react with hydration products of concrete,which aggravates carbonation corrosion and cracking of concrete.Increasing the compactness of concrete and improving the pore structure could reduce the penetration of corrosion medium into concrete,thus greatly improve the frost resistance of concrete under cattle urine erosion.