Permeability and porosity changes associated with cement grout carbonation

• Published in: Cement and concrete research 1991, Vol.21 (4), p.441-454
• Main Authors: Dewaele, P.J., Reardon, E.J., Dayal, R.
• Format: Article
• Language: English
• Subjects: Applied sciences; Buildings. Public works; Concretes. Mortars. Grouts; Exact sciences and technology; Grouts; Materials
• ISSN: 0008-8846; 1873-3948
• DOI: 10.1016/0008-8846(91)90092-V

Samples of water-saturated cement grout were carbonated under high pressure to evaluate the effect of carbonation on permeability and pore size distribution. Three methods were used to transport dissolved CO 2 into the grout samples: diffusion, 1-D advection and point source advection. Microscopic examination of cross sectioned samples from the 1-D advection experiment revealed that the carbonation front had only penetrated to a depth of 1.5 mm after two months of reaction. The other two methods produced less penetration. The failure of the three methods to produce significant penetration of carbonation indicates that the production of macroscopic carbonated grout samples is not feasible within an experimental time frame, under water-saturated conditions. In all three methods, CO 2 transport was effectively arrested due to marked changes in porosity and permeability accompanying the precipitation of carbonation alteration products within the pore networks. Porosimetry and optical analyses indicate that the larger macropores of the carbonated samples were preferentially filled with reaction products. Carbonated samples exhibit a smaller average pore radius and an increased pore surface area, as compared to non-carbonated samples. The pore volume distributions show marked increases in the lower pore radius range (2–3 nm) due to carbonation. Permeability reductions of between three and five orders of magnitude were calculated for fully-carbonated grout, using flow data from the 1-D advection experiments.