核电站大体积混凝土早龄期裂缝的影响因素

FACTORS INFLUENCING EARLY AGE CRACKS ON MASSIVE CONCRETE OF NUCLEAR POWER STATION

通过胶凝材料组分调整和水化热的测定分析,骨料级配的优化以及混凝土的自由收缩试验,对某核电站常规岛基础大体积混凝土早龄期裂缝的影响因素进行了试验研究。试验结果表明:优化胶凝材料的组分构成可降低水化热,减缓胶凝材料的水化速率;优化后的新配合比在保证混凝土抗压强度的基础上,加入聚丙烯短纤维后,混凝土的工作性仍能满足高坍落度泵送混凝土的要求;掺入纤维减少了混凝土的自由收缩,提高了混凝土抵抗收缩能力。通过模拟大体积混凝土绝热温升试验,结果表明优化后的新配合比可降低混凝土水化温升的峰值温度,进而可在一定程度上降低水化反应时大体积混凝土的温度应力,降低温度裂缝出现的概率;同时纤维的掺入使混凝土早龄期可见收缩裂缝明显减少。

Factors influencing early age cracks on massive power station are tested and researched through adjustment of concrete of routine island ingredients of cementing foundation of a nuclear material, hydration heat measurement and analysis, aggregate gradation optimization and free shrinkage test of concrete. The test results show that cementing pressure s optimization of ingredients of cementing material could reduce hydration heat and slow down material hydration; the optimized mix proportion of cementing material could not only guarantee the trength of concrete, but also satisfy the requirements of high-slump pumped concrete after polypropylene fiber is added; the fiber added could effectively reduce the free shrinkage of concrete and improve concrete performance against shrinkage. At last, adiabatic temperature rise test of massive concrete is carried out and test results show that the optimized proportion could reduce the peak temperature of concrete hydration temperature rise, and then reduce the temperature stress of massive concrete during hydration reaction and the probability of crack generation caused by temperature variation; meanwhile, the fiber added could obviously reduce visible early age shrinkage cracks.