微膨胀型中热水泥在三峡二阶段工程砼中的应用

三峡二阶段工程控制砼用水泥的MgO量为3.5％～5.0％,使砼具有自生体积微膨胀性质,以补偿砼硬化过程中的收缩应力,提高砼抗裂性。试样抽检和观测表明:用MgO量为3.5％～5.0％的微膨胀中热水泥配制砼,具有微膨胀性,最大膨胀量约55μm;一般半年至1年变形趋于稳定。2000年底对大坝砼裂缝调查统计是:无贯穿性裂缝,二类裂缝数为0.171条/万m3、三类裂缝数为0.048条/万m3,均低于三峡工程砼控制二类、三类裂缝数量≤0.5条/万m3要求,为确保三峡工程砼耐久性奠定了基础。

Application of microexpansion medium heat cement in the concrete engineering of 2nd phase of Three Gorge project

In the 2nd phase of the Three Gorge project, the MgO in the cement used for concreting is controlled within the range of 3.5%~5.0%, so that the concrete can have the property of self-generated volumetric microexpansion to compensate the contraction stress in the process of concrete hardening, so as to increase anti-cracking property of concrete. The sample testing and observation show that the concrete made of micro-expansion medium heat cement with MgO in the range of 3.5% ~ 5.0% has the micro-expansion property with the max. expansion of ca. 55 um. Normally the deformation becomes stable after half to one year. The investigation statistics to the cracks in the concrete of the dam at the end of 2000 reveals that there is no penetrating crack, the secondary crack is 0.171/10 000m3, tertiary crack is 0.048/10 000 m3, all below the figures of <0.5/10 000 m3 for both categories of crack required for the Three Gorge project, which provides a sound basis for the durability of the engineering concrete in Three Gorge project.