Micromechanical properties within the interphase between heterogeneous layers made of cementitious composites

Abstract

Abstract The article presents the evaluation of the micromechanical properties of the material within the interphase between heterogeneous layers made of cementitious composites. For this purpose, two different cementitious composites were selected in order to create a two-layer heterogeneous system. Cement mortar was applied as the overlay and concrete was used as the substrate. To treat the surface of the concrete substrate, four different methods, which are the most commonly used in the industry, were applied: patch grabbing of the surface of the substrate directly after casting (T1), casting against the steel formwork (T2), mechanical grinding (T3) and shot-blasting (T4). Mechanical properties were evaluated at micro-scale using the nanoindentation technique. In particular, the indentation modulus and hardness profiles in the vicinity of the interphase between the overlay and concrete substrate were assessed. It is shown that the micromechanical properties of the cementitious composite within the interphase change and depend on the selected surface treatment method. The results indicate a significant change of the indentation modulus and hardness within the interphase region between the overlay and concrete substrate with an approximate width of 150 µm. To support these observation, the back-scattered electron images of the interphase, gained using scanning electron microscopy, are presented.