Mechanical properties of polymer impregnated cement systems and the effect of moisture on their dimensional stability

Cement matrices were prepared by autoclaving portland cement-silica mixtures having various percentages by weight of silica, with water-to-cement ratios of from 0.22 to 0.45. Normal cement paste samples were also made for comparison. Samples were heated to 100°C in vacuum for 24 h before impregnation with methyl methacrylate monomer (MMA), which was then polymerized; impregnation was repeated for complete impregnation. Young's modulus and microhardness were measured as a function of volume fraction of PMMA and results compared with those obtained from similar samples conditioned to 11% RH. Autoclaved impregnated and unimpregnated specimens and room-temperature-cured cement paste specimens at both conditions were exposed to 100% RH and their length changes measured for up to four years. Permeation to water vapour in the impregnated specimens, although decreased, still occurs and impregnation increased long-term expansion on exposure. Expansion on exposure to 100% RH is much larger for D-dried than for 11% RH-conditioned matrices; the latter produced stronger bodies on impregnation.