酸雨环境下老旧砖砌体的抗压性能

为研究酸雨环境下老旧砌体抗压力学性能退化规律，实验室配置了PH值分别为1.5、2.5和3.5的3种硫酸和硝酸混合溶液来模拟酸雨环境，采用完全浸泡加速腐蚀的试验方法对砖、砂浆和砖柱进行不同程度的腐蚀，并测定其抗压强度。试验表明，随着腐蚀时间的增加，砂浆试块抗压强度先增大后降低；砖试块抗压强度随腐蚀时间的增加而降低；模拟酸雨溶液PH值越小，砂浆和砖试块抗压强度降低程度也愈大；砖柱极限承载力和弹性模量均随腐蚀时间的增加而降低，且模拟酸雨溶液PH值越小，降低程度愈大；随着腐蚀时间的增加，砖柱初始刚度逐渐减小，极限破坏位移增大；模拟酸雨溶液PH值越小，砖柱在达到峰值荷载时的变形值越小，脆性愈大；基于试验结果，建立了酸雨环境下砖柱应力应变曲线上升段统一数学表达式及酸雨侵蚀后普通烧结粘土砖砌体剩余抗压强度回归公式。

Compression properties of old brick masonry in acid rain environment

Three kinds of mixed solutions of sulfuric acid and nitric acid with the pH value of 1.5, 2.5 and 3.5 were prepared in the laboratory to simulate acid rain environment. The compression properties of brick masonry exposed to acid rain environment was studied. The brick samples, mortar samples and brick-columns were completely immersed in the simulated acid solutions. After being exposed to the solutions for a certain period, compression tests were performed on the three types of the samples. The results showed that with the increase of corrosion time the compressive strength of mortar samples increased firstly and then decreased, whilst the brick samples always decreased. And the lower the pH value of the solutions was, the more the compressive strength of mortar samples and brick samples decreased. With the increase of corrosion time, the ultimate bearing capacity and elastic modulus of brick-columns showed a trend of decrease, and the lower the pH value of the solutions was, the more obvious the trend was. With the increase of corrosion time, the initial stiffness of brick-columns decreased, ultimate failure displacement increased. With the pH value of the solutions declining, the deformation of brick-columns under ultimate load decreased but the brittleness increased. Based on the experimental results, regression formulas were put forward to describe the ascending part of the stress-strain curve and the remaining compressive strength of brick-columns exposed to acid rain environment.