A Numerical Method For Predicting The Water Permeability Coefficient Of Cement Paste

As a complex porous material,cement paste is mainly composed of gel product and pores generated from the hydration reaction of cement.The pore structure in cement paste directly affects the water permeability coefficient of cement paste.The water permeability coefficient is an important index of the durability of concrete,and plays an important role in the design and assessment of concrete materials.Based on the simulated microstructure model of cement paste,the random walk algorithm is used to predict the water permeability coefficient of cement paste.This study mainly includes the following three aspects:The principles of hydration reaction are used to reconstruct the microstructure of cement paste on the microscopical level and to further evaluate the degree of hydration and the capillary porosity.Through comparison with the experimentally measured values and the empirical formula,the validity of the cement hydration model is verified.The effects of the water/cement ratio and temperature on the degree of hydration are analyzed in a quantitative manner.Based on the reconstructed structure of simple porous materials on the microscopical level,a random walk algorithm is presented for predicting the water permeability coefficient.Through comparison with the numerical solution of the Stokes equation,the validity of the random walk algorithm in predicting the water permeability coefficient of simple porous materials is preliminarily verified.Based on the reconstructed structure of cement paste on the microscopical level,the random walk algorithm is used to compute the water permeability coefficient.Through comparison with the effective medium method,the validity of the algorithm is verified.At the same time,the limitation of the algorithm is also analyzed in detail.The effects of the water/cement ratio,temperature and the cement diameter on the water permeability coefficient of cement paste is analyzed in a quantitative manner.