323 / 2019-09-30 14:21:54

Cement shape effect on the microstructure and diffusivity of cement paste from fresh state via non-spherical cement hydration to hardened state

Non-spherical cement particles,Hydration,Microstructure,Diffusivity

计算流体力学、多场耦合、生物力学、动力学等 > 多尺度建模与分析

Microstructures generated by hydration of various components in cement are important sources for determining the physical and mechanical properties of cement-based materials. The shape of cement particles is normally simplified as sphere in most cement hydration models. However, the actual shape of cement particles is non-spherical. To assess the effect of cement shape on the evolutions of the microstructure and diffusivity of cement paste, a microstructure-based model of non-spherical cement particles is proposed. In this paper, five kinds of Platonic particles and sphere are chosen to represent the shape of cement particles, and the geometric construction of hydration products are simulated based on mathematical morphology methods. Meanwhile, the degree of hydration of non-spherical cement is derived by introducing the sphericity as a shape descriptor. The decrease of sphericity results in the increase of hydration degree and the decrease of porosity of cement paste under the same hydration time conditions. This is due to that the decrease of sphericity increases the specific surface area of cement particles. Subsequently, the microstructure of cement paste consisting of hydration products, anhydrous cement particles and pores is voxelized, and a random walk algorithm is adopted to calculate the diffusivity of cement paste with such the microstructure. Results show that the relative diffusivity increases with the increase of sphericity and water cement ratios. This reveals that the larger sphericity corresponds to the smaller specific surface area, and resulting in the less hydration products and more porosity, which ultimately increases the relative diffusivity.