Study of the transition zone of concretes prepared with metakaolin using sem/eds-associated nanoindentation technique

Abstract

The instrumented nanoindentation technique using significantly small loads is a viable alternative for specific studies in the interfacial transition zone (ITZ) of concrete. This study analyses the properties of the transition zone of concretes prepared with metakaolin (MK) using the nanoindentation technique and SEM/EDS. The response variables adopted were the thickness of the transition zone, nano-hardness and modulus of elasticity, and the formation of high- and low-density C-S-H in the transition zone. Incorporating MK and decreasing porosity and CH content in concretes can increase the percentage of frequency of CSH in the cementitious matrix. Reduced ITZ is a direct consequence of these reported effects. However, this beneficial effect of MK on ITZ is more pronounced in concretes with poorer cement consumption. The incorporation of MK has a more discreet influence on concretes with high cement consumption − C60, with 512 kg/m³ , for example, had a similar behavior to C60 8% MK. The analysis of the ITZ thickness by nanomechanics and nanoindentation techniques presented results very similar to those of the chemical analysis (EDS).