基于水化度的混凝土自收缩特性的细观研究

Mesocosm study on characteristic of autogenous shrinkage for concrete based on hydration degree

采用混凝土多相复合材料模型,编制了基于水化度的混凝土温度场、湿度场和应力场仿真计算程序以及全自动的混凝土随机骨料建模程序,从细观角度研究了温度历程和混凝土自干燥效应引起的自身相对湿度对混凝土自收缩特性的影响.分析结果表明:骨料和砂浆在湿度场和应力场中表现出不同的分布特性,两者之间的粘结带很有可能是内部自收缩裂缝的启裂位置;温度历程对自收缩特性的影响是较为明显的;随机骨料的具体投放对细观分析至关重要;建立适合细观分析结果的整体评价模型,有助于更好地诊断开裂风险和防止裂缝的发展.考虑了多相材料特性差异及温、湿度影响的细观模型和计算方法能够更真实地揭示混凝土自收缩变形的内在机理及其致裂机理.

The simulation of temperature,humidity and stress fields based on the equivalent age method and the fully automatic modeling tool of aggregates was carried out.The influence of two factors,tempe-rature history and autogenous relative humidity due to self-desiccation,on autogenous shrinkage in concrete was studied from the mesocosmic view.It is concluded that the aggregate and matrix show distinct distribution properties in humidity field and stress field,the aggregate-matrix interface has high possibility to become the location of the initial cracking caused by AS,the temperature history is the main factor affecting the autogenous shrinkage,and the distribution of random aggregates is extremely important for mesoscopical analysis.It is beneficial for better estimating cracking risk and preventing cracking development through establishing whole evaluation model fitting to micro-results.In a word,the inherent mechanism and cracking mechanism of autogenous shrinkage can be explained more reasonably by using above mesoscopic model and calculation method.