Characterizing Porosity and Diffusive Properties of Monolithic Cement-Based Solidified/Stabilized Materials

Abstract

This paper presents the application of a single reservoir diffusion test to determine both the effective porosity of a soil-cement matrix and the diffusivity of tritium through saturated, monolithic, cement solidified/stabilized wasteforms. Testing was performed on a laboratory mixture of cement paste, sand, and kaolinite. The influence of porosity on the proper interpretation of the diffusion tests was examined. Results of tests on three replicate specimens were consistent and indicate effective porosities of 0.26 to 0.28 and effective diffusive coefficients of 2.5 x 10(-10) to 3.0 x 10(-10) m(2)/s. The effect of curing time is discussed. Products of the effective diffusion coefficients and porosity (n(e)D(e)),) decreased by 22 % from specimens cured for 14 days to specimens cured for 28 days prior to testing while from 70 to 126 days of curing n(e)D(e) only changed by 8 %. This suggests that curing should be carried out for greater than 70 days prior to conducting these tests.