干热养护对活性粉末混凝土力学及收缩影响研究（英文）

Influence of dry heating regime on the mechanical and shrinkage properties of reactive powder concreteInfluence of dry heating regime on the mechanical and shrinkage properties of reactive powder concrete

目的:高温干热养护工艺对活性粉末混凝土的力学强度及收缩性能有重要影响。本文针对不同的高温养护温度和时间分析活性粉末混凝土材料的抗压强度、抗折强度、收缩和微观结构,探索高温干热养护环境提升活性粉末混凝土材料力学性能的机理,并讨论外部环境湿度对材料收缩变形的影响。创新点:1.通过调整不同养护工艺参数,大幅度提升活性粉末混凝土的早期强度;2.建立试验模型,成功模拟适应性冲压工艺过程。方法:1.通过实验分析,研究不同养护温度和养护时间对活性粉末混凝土力学强度的影响(表4);2.通过设计不同的养护湿度(50%和90%),构建后期养护环境与材料干燥收缩之间的关系,得到适应性的后期养护参数(表5);3.通过与已有研究的分析对比,提出适用于工程实际的高温干热养护工艺参数,并得出后期高湿度养护降低活性粉末混凝土收缩的微观机理(图7)。结论:1.通过调整高温养护的温度和养护时间可以对活性粉末混凝土的强度产生影响。2.试件在经历高温养护后再进行高湿度养护可以有效降低材料的后期干燥收缩。3.材料界面过渡区在高温养护条件下变得更加密实;在高温环境下生成托勃莫来石或硬硅钙石是材料获得较高强度的主要原因。

The influence of the curing temperature (150℃,200℃,250℃,and 300℃)and curing time (4h,8h,and 12h)on the mechanical properties and shrinkage development of reactive powder concrete (RPC)was studied,and a curing regime for improving its mechanical properties is proposed.Test results show that the compressive and flexural strengths of specimens increase at curing temperatures of 200℃ to 250℃,but decrease at curing temperature of 300℃.Meanwhile,shrinkage measurement results indicate that the ultimate shrinkage of high-temperature cured RPC at 50% relative humidity (RH)is lower than in the control group.Scanning electron microscope results reveal that high-temperature curing improves the microscopic pore structure of RPC and makes the interfacial transition zone denser.Furthermore,the dry-heat curing regime can accelerate the cement hydration process,and tobermorite or xonotlite was found to be one of the major crystalline hydrates at high temperature.