ABSTRACT
Abstract Pore solution studies have played a prominent role in investigations relating to
general cement chemistry and concrete durability problems. Several authors have raised the question of whether the pore solution concentrations obtained in the usual manner (under high triaxial stresses) truly represent the bulk composition of the pore fluid. This report presents parallel determinations of pore solution of mature hydrated cement pastes determined in the usual manner, and separately, in a procedure in which pore solution were recovered at incrementally increasing pressures. Pore solution of mature hcps are predominantly alkali hydroxide, with some S04 2-ions and very small concentrations of Ca2+ ions. There was only a small effect of pressure on the concentrations ofthe major components, the increase between the ion concentrations at the lowest and the highest pressures used varied from about 7% to 16%. On the other hand, sot ion concentrations increased significantly with increasing pressure, here the SO/ ions increases were on the order of 0.01 to 0.02 N over the full pressure range, insignificant in terms of the total ionic concentrations (0.5 to 0.8N) but representing 65% to 75% of the concentrations obtained at the lowest pressure. It was concluded that pore solutions expressed from hcps over the range of pressures usually employed provide an appropriate measure for the actual concentration of the major ions present in the pore fluid. Keywords: Pore solution analysis, pressure effects.
