MgO膨胀剂在水工混凝土中的极限掺量研究

Study on limit contents of MgO expansion agent in hydraulic concrete

为了满足水工大坝对外掺MgO混凝土自生体积膨胀变形的需要和促进外掺MgO混凝土的推广应用,提出采用砂子等量替代混凝土中的粗骨料拌制"模拟砂浆"试件进行压蒸实验。结果表明,采用该法测得的压蒸膨胀率均比采用水泥净浆、水泥砂浆、一级配混凝土作为压蒸试件的测值低,由此确定的混凝土的MgO极限掺量均比现行方法高;若以压蒸膨胀率随MgO掺量变化曲线的拐点对应的MgO掺量作为混凝土的MgO极限掺量,则当粉煤灰掺量为40%时,采用"模拟砂浆"试件确定的MgO极限掺量可达到12%。

In order to meet the requirement for the autogenic volume-expanding deformation of hydraulic concrete mixed with light-burned magnesium oxide （MgO）and promote the application of MgO concrete,the autoclave test was carried out with “simulation mortar”specimen which using equivalent amount sand to replace coarse aggregate in the concrete.The result shows that the autoclave-treated expansibility of the specimen made by this simulation method was smaller than that of cement paste,cement mortar and grade-one concrete and the MgO limit contents acquired by this method is higher than current methods.If the MgO limit contents are determined at the MgO contents correspond to the inflection point of the curve that the autoclave-treated expansibility var-ying with MgO contents,then the MgO limit contents can reach 12% with simulation mortar specimen when the fly ash content was 40% in the concrete.