养护对超高性能混凝土强度和显微硬度的影响

Effect of curing condition on mechanical strength and micro-hardness of ultra-high performance concrete

为优化预制电缆沟用超高性能混凝土(UHPC)的养护制度,研究了不同养护条件对超高性能混凝土力学性能和显微硬度的影响,运用概率统计分析方法进行了UHPC的显微硬度数据处理,并结合电镜分析阐明其作用机理。结果表明,组合热养护制度比常温养护和单一的加热养护制度更有利于提高7 d早期强度,但电镜分析发现150℃干热养护条件下混凝土水化产物较为粗大,孔洞率高且有微观结构开裂,这解释了混凝土28 d强度发生倒缩的现象;组合热养护混凝土在后期经过标准养护后,56 d抗压强度继续增长,高于160 MPa,可满足预制电缆沟的强度要求。

For the aim of curing regime optimization of the prefabricated cable trench,the influence of different curing condition on mechanical properties and micro-hardness of ultra-high performance concrete(UHPC)was investigated.the micro-hardness data of UHPC was processed by probabilistic statistical methods,and action mechanism of curing was clarified by scanning electron microscopy(SEM).The results indicate that compared with normal temperature curing and single curing condition,the combined curing condition significantly improves the 7 d early age mechanical properties of UHPC.However,the SEM analysis shows that during 150℃dry air heating in the combined curing,the morphology of concrete hydration products are bigger and the microstructure characteristics of concrete is higher porosity with some visible cracks.The results of micro structural tests explain the phenomenon that the 28 d age strengths of concrete are lower than 28 d age strengths.The 56 d age strengths of high temperature combined curing concrete continue to increase in subsequent standard curing condition and are higher than 160 MPa which can meet the strength requirement of prefabricated cable trench.