针对水利水电工程挡水坝常用的三级配粉煤灰混凝土,采用压蒸试验、自生体积变形观测、压汞分析、电镜扫描、X射线能谱等方法,对水泥砂浆、一级配混凝土的压蒸膨胀变形与龄期长达6a的三级配外掺MgO混凝土自生体积变形的关联性进行了研究.结果表明:外掺MgO混凝土的自生体积膨胀变形与水泥砂浆、一级配混凝土的压蒸膨胀变形没有关联性.现行以水泥砂浆试件或一级配混凝土试件的压蒸膨胀变形曲线拐点或压蒸膨胀率为0.5%确定的坝体混凝土的MgO极限掺量,虽能够保障混凝土大坝安全运行,但未能反映外掺MgO混凝土膨胀变形的实际情况.%Relationship between the autoclave-treated expansibility of cement mortar, one-graded concrete and the autogenous volume deformation of three-graded MgO-mixed concrete at six-year age for the three-graded fly ash concrete commonly used in water retaining dams of water conservancy and hydropower engineering were studied based on the methods such as autoclave-treated test, autogenous volume deformation observation, mercury intrusion porosimetry, scanning electron microscopy, energy-dispersive X-ray spectroscopy and so on. The results indicate that there is no relevance between the autoclave-treated expansibility and the autogenous volume deformation. The current standard to determine the limit MgO content in dam concrete is based on the inflection point of the autoclave-treated expansibility curve or the autoclave-treated expansion ratio at 0.5% of cement mortar and one-grade concrete samples. This standard can ensure the safety operation of a concrete dam but the actual expansive deformation of MgO-mixed concrete cannot be reflected.
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