High-pressure epoxy-impregnated cementitious materials for microstructure characterization

High-pressure fluorescent epoxy impregnation (>20 bar) of cement-based materials is compared to the more conventional method of vacuum impregnation. Parameters such as the epoxy resin penetration depth and the stability of the fluorescence intensity are evaluated in order to determine the effectiveness and reliability of the aforementioned methods in preparing paste and mortar samples for microstructure characterization. An evaluation of polymer loading as a function of impregnation pressure reveals a saturation pressure ( P-sat) at which complete filling of the pores is achieved. The evolution of the fluorescent epoxy resin penetration front is examined under ultraviolet (UV) light, and correlated to the impregnation pressure. Results clearly indicate that high-pressure impregnation is a more effective and faster method to imbed epoxy resin in cementitious materials. Furthermore, P-sat is a parameter that is sensitive to a material's microstructure, particularly in pastes samples of high water-to-cement ratios (W/C) which reveal a polymer overloading point. Fluorescence stability of the high-pressure-impregnated sample is compared to that of the vacuum-impregnated sample. Results show that the high-pressure-impregnated samples have a higher intensity and stability. (C) 2002 Elsevier Science Ltd. All rights reserved.