Microstructure-based modelling of drying shrinkage and microcracking of cement paste at high relative humidity

Abstract

In order to comprehensively understand the drying behavior of cementitious materials, this paper presents a microstructure-based model to simulate the water evaporation process in capillary pores, the drying-induced deformation of cement paste with free boundary condition and the microcracking of cement paste under constraint. This model is applicable to high relative humidity ranges where the capillary pressure effect quantified by the Kelvin equation is the primary loading stimulus. Mainly two parts of modeling work are carried out. (1) From a microstructure model of cement paste HYMOSTRUC3D, the water evaporation in capillary pores is captured by a multi-step digitalization algorithm. (2) The drying-induced shrinkage deformation and internal microcracking of hardened cement paste with different boundary constraints are simulated by a 3D lattice fracture model. In order to reduce the computational cost, a two-scale modeling regime is employed where the microstructure of cement paste and the nanostructure of C-S-H are incorporated. Experimental test about free shrinkage of cement paste is utilized to validate the model. At last, the model is compared with poro-elastic-mechanical models, and is applied to study the influences of water-to-cement ratio and hydration time on the free shrinkage as well as the influence of constraints on the internal microcracking.