特高拱坝专用低热硅酸盐水泥研究与应用

Development and application of specific low heat portland cement for building ultra-high arch dams

特高拱坝应力水平较高,对坝体混凝土整体性、安全性和耐久性要求更高,要求大坝混凝土具有较高的强度等级、抗渗等级和抗冻等级,以及较高的综合抗裂能力,为此研究了一种专门用于特高拱坝的低热硅酸盐水泥(简称"低热水泥")。根据低热水泥矿物组成与强度、水化热的影响规律,确定了专用低热水泥四种主要矿物的适宜含量;控制MgO含量在4%~5%之间以补偿混凝土温降收缩;控制比表面积不大于340 m^2/kg以减缓水泥早期水化速度。提出专用低热水泥技术要求并制定了相应的标准,采用符合该标准的专用低热水泥配制的大坝混凝土单位用水量较低、后期强度较高、绝热温升较低、综合抗裂性能较强。建立了专用低热水泥生产工艺全过程质量控制精细化管理与监造体系,实现了专用低热水泥的规模化稳定生产,为300 m级特高拱坝以及其他水电工程应用低热水泥奠定了良好的基础。

Ultra high arch dams have higher stress levels and higher requirements of integrity, safety and durability of concrete dam bodies, which requires dam concrete to have higher strength grade, penetration resistance, frost resistance, and crack resistance. In this study, we have developed a specific low heat Portland cement that is suitable for the production of such dam concrete for ultra high arch dams. For this new type of cement, suitable contents of its four major mineral components were determined by considering the comprehensive effects of cement mineral composition, material strength and hydration heat. Its MgO content was controlled in the range of 4%-5% to compensate thermal shrinkage during concrete temperature drop, and its specific surface area was limited to no greater than 340 m^2/kg to reduce cement hydration rate at early stage. A new standard, Technical Requirements of Low Heat Portland Cement for Arch Dams, is suggested in this study and the corresponding design criteria are set to control cement quality. The dam concrete made of the specific cement that meets this standard will have a satisfactory performance in low unit water consumption, low adiabatic temperature rise, and high crack resistance. For this specific cement, a management and supervision system of quality control for the whole procedure has already been established and its large-scale steady production is achieved. Thus all this has laid a solid basis for application of low heat Portland cement in construction of 300 m high arch dams and other hydropower projects.