W/C ratio estimation of concrete through optical microscopy, electron microscopy and thermogravimetric analysis

Abstract

W/C is a fundamental parameter for concrete mix design, it defines the properties in the fresh and hardened state as well as the durability of the material. Nevertheless, once the concrete has hardened, it is very difficult to estimate the W/C in the original mix design, so far only 2 methodologies has been accepted as a standards. Because of this, the aim of the research is to use 4 methodologies, circular polarization microscopy (CPL), thermogravimetric analysis (TGA), UV light microscopy and scanning electron microscopy (SEM) + Powers and Brownyard approach to estimate the W/C of different concrete samples from a Round Robin Test done by the Applied Petrography Group (APG). The results showed that all the techniques have a correlation with the W/C. The CPL on its own and in combination with the UV light can be a feasible technique to estimate this value. Furthermore, since there were several techniques, it was decided to choose which one gave the best results using three guidelines, representativeness, reproducibility and reliability. The technique with the highest score was the combination of CPL+UV light.