Modeling of microstructural effects on the creep of hardened cement paste using an experimentally informed lattice model

This paper presents a method to numerically investigate the microstructural effect on the creep behavior of cement paste at the microscale. The lattice fracture model is extended to consider local time-dependent deformations of calcium-silicate-hydrate phases in the cement paste by imposing local forces. The term “experimentally informed model” is used herein as the heterogeneous microstructures of hardened cement pastes were obtained by using the X-ray computed microtomography and directly implemented into the model. The mechanical and creep properties of different constituents at the resolution of 5 µm were inversely identified from the fracture and creep bending tests on cementitious microcantilever beams at the microscale. The model is then validated through the comparison with the testing results of cement pastes with different w/c ratios and microstructures. It is found that the developed model can successfully reproduce experimentally observed behaviors and be applied to explain the experimental results in detail. With the method presented in this paper, the relationship between the volume fractions of different components and the global creep behavior of cement paste can be established. The validation of the model performed at the microscale forms a basis for the multiscale analysis of concrete creep.