硫酸盐侵蚀水泥砂浆动弹性模量的超声检测

DYNAMIC MODULUS OF CEMENT MORTAR IN SULPHATE EROSION MEASURED BY ULTRASONIC CHECKING

用普通硅酸盐水泥,分别配制了水灰比在0.4～0.8范围内的水泥砂浆试件进行硫酸盐加速侵蚀实验。运用超声波技术测定了不同浓度硫酸盐侵蚀下不同水灰比水泥砂浆试件的动弹性模量值,分析了此实验条件下试件动弹性模量随侵蚀时间变化的规律,并对实验结果作了简要的机理分析。结果表明:在硫酸盐侵蚀条件下,水泥砂浆试件的动弹性模量随侵蚀时间首先增大至某一峰值,随后迅速降低或者逐渐缓慢降低。水灰比和硫酸根浓度对动弹性模量的影响只是反映在数值上;硫酸盐对水泥砂浆材料的侵蚀是由表及里的,动弹性模量的演化可以来反映试件整体平均强度的变化,而回弹法测定的抗压强度反映的是试件表面强度的变化。比较而言,动弹性模量的演化在时间上存在着滞后性。试件微观分析及宏观形貌表明:硫酸盐侵蚀条件下,砂浆试件动弹性模量的演化主要是膨胀产物钙矾石等的形成引起砂浆内部微观结构变化的缘故。

The accelerated sulphate erosion test for common portland cement mortar specimen prepared with water cement ratio from 0.4 to 0.8 was carried out, and the dynamic modulus variation of the specimen to the erosion time was determined by ultrasonic checking method. The correspondence of dynamic modulus with erosion time was analyzed. Experiment results show that the dynamic modulus of cement mortar in sulphate erosion increases to a peak with the increase of erosion time and then decreases rapidly or gradually, and effects of water cement ratio and sulfate concentration on the dynamic modulus are obvious numerically. Cement mortar in sulfate is eroded from surface to inside. The evolvement of dynamic modulus shows the average strength change of the specimen, while the compressive strength measured by rebound method shows the surface strength change of the mortar. There is a hysteresis phenomenon for evolvement of dynamic modulus comparing to the compressive strength by rebound method. The results of micro-analyses and macroscopic morphology indicate that the evolvement of dynamic modulus depends on the micro-structural change of mortar because of the formation of expanded products (ettringite etc.) in sulfate erosion.