Application of multiple techniques to quantify pore structure of degraded cementitious materials.

Carbonation and leaching of concrete are considered as the main degradation processes for many important applications (e.g. nuclear waste facilities, hydro structures) because of its importance for long-term durability assessment even with extremely slow processes. The degradation modifies the microstructure of cement-based materials from nano-scale up to microand meso-scale. However, there is no unique technique able to characterize these microstructural changes at the different scales. In this study, we introduced a combined method in which N2-adsorption, mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) were used to quantify the microstructural changes at nano, sub-micro, and micro level, respectively. With this approach, we obtain a larger range of pore size distribution and minimize the limitations of each technique. The characterizations were performed on sound, leached and carbonated cement pastes with different w/p ratios and limestone filler replacements. The leached and carbonated materials were obtained under accelerated conditions using ammonium nitrate solution and elevated pressure of pure CO2, respectively.