Experimental and numerical evaluation of mechanical properties of interface between filler and hydration products

The interface between filler and hydration products can have a significant effect on the mechanical properties of the cement paste system. Surface analysis techniques and mechanical model can be used to study the mechanical properties of the interface. These studies can provide insight into the adhesion mechanisms between filler and hydration products. In this paper, cement pastes blended with fillers (micronized sand and limestone powder) are discussed. Crack paths and fracture surfaces of loaded cement pastes were investigated by scanning electron microscopy (SEM) observation. Parallel with the SEM observations, the influence of interface properties on crack propagation, tensile strength and fracture energy was studied numerically by using a lattice model. With these SEM observations and simulation results the mechanical properties of the interface between filler and hydration products were evaluated. Limestone powder exhibited superior bond characteristics with hydration products compared with micronized sand. Furthermore, it suggests that the limestone-hydration products interface is even stronger than hydration products. This is likely due to the strong electrostatic interactions or the iono-covalent forces between limestone particles and C-S-H particles.