基于电阻率法的预裂纹水泥浆体环开裂性能研究
发布时间：2018-10-05 14:23
【摘要】：混凝土早期开裂降低了混凝土的耐久性,开裂问题成为研究热点问题。目前研究开裂问题的方法很多,但尚未形成一个标准方法,本文基于预裂纹水泥浆体环开裂实验,提出了一种快速预测水泥浆体环开裂时间的方法——电阻率法。采用预裂纹水泥浆体环开裂装置研究了水灰比、水泥等级对预裂纹水泥浆体环开裂时间的影响。结果表明:同一水泥等级的水泥浆体环,不同水灰比对开裂时间的影响有相同的趋势,即水灰比越低,水泥浆体环开裂时间越早。P?C32.5的水泥浆体环开裂时间与水灰比变化曲线位于P?O42.5的水泥的上方,即同一水灰比水泥浆体环,水泥等级越高,水泥浆体环开裂时间越早。采用电阻率法研究了水灰比、水泥等级对水泥浆体1440 min(24 h)内电阻率曲线和其变化速率曲线的影响。结果表明:在水泥等级相同的条件下,低水灰比水泥浆体的电阻率曲线始终在高水灰比水泥浆体电阻率曲线的上方,其电阻率变化速率曲线的3个极大值点出现的时间越早。在水灰比相同的情况下,在水化早期P?O42.5水泥浆体的电阻率小于P?C32.5的电阻率,但是在水化后期P?O42.5水泥浆体的电阻率却高于P?C32.5的电阻率,P?O42.5水泥浆体的1440 min内电阻率变化速率曲线的3个极大值点出现时间的比P?C32.5的早。在预裂纹水泥浆体环开裂实验和电阻率实验基础上,得到了水泥浆体24 h(1440min)的电阻率越大,预裂纹水泥浆体环开裂时间越早;建立了水泥浆体环开裂时间与水泥浆体24 h电阻率的关系式;提出了用水泥浆体24 h电阻率来预测水泥浆体环开裂时间的方法。利用ANSYS热——结构耦合场模拟水泥浆体环湿度场变化时程进而得到水泥浆体内部最大拉应力变化时程,对比实际抗拉强度得到开裂时间,为研究开裂问题提供了一种可供借鉴的方法。
[Abstract]:The early cracking of concrete reduces the durability of concrete. At present, there are many methods to study the cracking problem, but no standard method has been formed. Based on the cracking experiment of pre-cracked cement paste, a new method, resistivity method, is proposed to predict the crack time of cement paste ring quickly. The effects of water-cement ratio and cement grade on crack time of pre-cracked cement paste ring were studied by using pre-cracked cement paste ring cracking device. The results show that the influence of different water-cement ratio on the cracking time of cement paste ring with the same cement grade has the same trend, that is, the lower the water-cement ratio, the earlier the crack time of cement paste ring. The C32.5 cement paste ring crack time and water-cement ratio change curve is located in P? The higher the cement grade is, the earlier the cracking time of cement paste ring is. The effects of water-cement ratio and cement grade on the resistivity curve and the change rate curve of cement paste in 1440 min (24 h) were studied by resistivity method. The results show that under the same cement grade, the resistivity curve of low water-cement ratio cement paste is always above the resistivity curve of high water-cement ratio cement paste, and the three maximum points of the resistivity change rate curve appear earlier. In the case of the same water-cement ratio, in the early stage of hydration, P? The resistivity of O42.5 cement paste is less than that of P? The resistivity of C32.5, but at the later stage of hydration? The resistivity of O42.5 cement paste is higher than that of P? C32.5 resistivity? In 1440 min of O42.5 cement paste, the ratio of the time to appear of the three maximum points of the resistivity change rate curve is P? C32.5 early. On the basis of crack test and resistivity experiment of pre-cracked cement paste, the higher the resistivity of cement paste is 24 h (1440min), the earlier the crack time of pre-cracked cement paste ring is. The relationship between the crack time of cement paste ring and the 24 h resistivity of cement paste is established, and the method of predicting the crack time of cement paste ring with 24 h resistivity of cement paste is put forward. The ANSYS thermal-structural coupling field is used to simulate the time history of moisture field change in cement paste ring, and then the maximum tensile stress change time history of cement slurry is obtained, and the cracking time is obtained by comparing the actual tensile strength. The method can be used for reference in the study of cracking problem.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528
[Abstract]:The early cracking of concrete reduces the durability of concrete. At present, there are many methods to study the cracking problem, but no standard method has been formed. Based on the cracking experiment of pre-cracked cement paste, a new method, resistivity method, is proposed to predict the crack time of cement paste ring quickly. The effects of water-cement ratio and cement grade on crack time of pre-cracked cement paste ring were studied by using pre-cracked cement paste ring cracking device. The results show that the influence of different water-cement ratio on the cracking time of cement paste ring with the same cement grade has the same trend, that is, the lower the water-cement ratio, the earlier the crack time of cement paste ring. The C32.5 cement paste ring crack time and water-cement ratio change curve is located in P? The higher the cement grade is, the earlier the cracking time of cement paste ring is. The effects of water-cement ratio and cement grade on the resistivity curve and the change rate curve of cement paste in 1440 min (24 h) were studied by resistivity method. The results show that under the same cement grade, the resistivity curve of low water-cement ratio cement paste is always above the resistivity curve of high water-cement ratio cement paste, and the three maximum points of the resistivity change rate curve appear earlier. In the case of the same water-cement ratio, in the early stage of hydration, P? The resistivity of O42.5 cement paste is less than that of P? The resistivity of C32.5, but at the later stage of hydration? The resistivity of O42.5 cement paste is higher than that of P? C32.5 resistivity? In 1440 min of O42.5 cement paste, the ratio of the time to appear of the three maximum points of the resistivity change rate curve is P? C32.5 early. On the basis of crack test and resistivity experiment of pre-cracked cement paste, the higher the resistivity of cement paste is 24 h (1440min), the earlier the crack time of pre-cracked cement paste ring is. The relationship between the crack time of cement paste ring and the 24 h resistivity of cement paste is established, and the method of predicting the crack time of cement paste ring with 24 h resistivity of cement paste is put forward. The ANSYS thermal-structural coupling field is used to simulate the time history of moisture field change in cement paste ring, and then the maximum tensile stress change time history of cement slurry is obtained, and the cracking time is obtained by comparing the actual tensile strength. The method can be used for reference in the study of cracking problem.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528
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