全坝外掺MgO混凝土筑坝技术在贵州省拱坝工程中的应用

Application of damming technology with MgO admixed concrete used in the whole dam in Guizhou's arch dam projects

为促进外掺MgO混凝土的推广应用和深入研究,对贵州省采用全坝外掺MgO混凝土筑坝技术建成1 a以上的8座拱坝的混凝土变形、诱导缝设置与施工等情况进行了总结和分析。分析结果表明:拱坝结构的超静定特性为外掺MgO混凝土在膨胀变化过程中形成预压应力提供了良好的约束环境;按照现行的水泥砂浆压蒸法或一级配混凝土压蒸法确定的MgO掺量制备外掺MgO混凝土,坝体混凝土的实测膨胀量多为50×10^(-6)~150×10^(-6),未完全达到补偿温降收缩所需的设计期望值;设置诱导缝是充分利用外掺MgO混凝土筑坝技术优越性的有效措施;在碾压混凝土中外掺MgO材料,有利于同时发挥碾压混凝土和外掺MgO混凝土快速、经济筑坝的优越性。

In order to promote the application and deep research of MgO-admixed concrete,the conditions of concrete deformation,configuration and construction of induced joints for 8 arch dams in Guizhou Province were analyzed.These arch dams were constructed with MgO-admixed concrete in the whole dam body and have been in operation for more than a year.Results show that the statically indeterminate property of the arch dam structure provides a good constrained environment for MgO-admixed concrete to form compressive pre-stresses during the concrete expansion process.The amount of MgO in the concrete can be determined by cement mortar autoclave method or one-grade concrete autoclave method.The measured expansion capacity of dam concrete with such amount of MgO is about 50×10^-6-150×10^-6,which does not reach the expected value to fully compensate the shrinkage crack induced by temperature drop.Configuration of induced joints is an efficient measure to take full advantage of the MgO-admixed concrete damming technology.Once the MgO materials is mixed into the roller compacted concrete（RCC）,the fast and economical superiority of RCC and MgO-admixed concrete in dam construction can take great effect.