The Evaluation Method of Curing Effect on Pore Structure Formation and Initial Stress in High Performance Concrete

点击翻译按钮获取中文摘要

The purpose of this study is to develop a method to evaluate the initial stresses and the micro pore structure formation in self-compacting high performance concrete. For this purpose, a theory of the consumption and transfer of moisture in the pore structure, development of micro pore structure of hydration products according to hydration progress and the production and transfer of thermal energy was constructed based upon thermodynamical concepts. This enables a rational evaluation of the influences of drying, heat and external loads introduced to high performance concrete at early ages in an overall evaluation system.At first, the hydration heat model of cement based on the arrhenius's law of chemical reaction was proposed under arbitary temperature history, in which the chemical composition of cement used and mix proportion of concrete were adopted as imput data. As next step, the micro pore structure development in concrete was formulated in terms of the hydration progress, where … More the linearity of bulk porosity in the hydrated cluster around the particles were assumed. Also, the moisture transport and distribution model in concrete was proposed by considering the thermodynamic equilibrium of moisture in the pore in a unified adsorption condensation process. Furthermore, the prediction model of volumetric change in concrete due to drying was proposed through the evaluation of maximum pore size saturated by pore water and surface tension given by moisture transport model. Besides, the constitutive law was also proposed to predict the permeability of concrete, considering the random geometrical characteristics of micro-pore structure. Finally, these generalized models of simulation were systematically integrated with rational consideration of relations among them as FEM program "DuCOM3" on the behavior of high performance concrete at early ages. The proposed models were verified through versatile experimental data with respect to time, such as temperature rise, strength development, weight loss, volume change, pore structure distribution and so on. Less