Effect of Carbonation on the Properties of Silty and Sandy Soils Treated with Lime and Cement

Abstract

Laboratory investigations on the carbonation of lime- and cement-treated soils were mostly conducted by using a carbon dioxide content up to about 10%, which is much higher than atmospheric carbon dioxide (≈0.03%). Therefore, the present study examines the physicochemical, pore structure, and compressive strength evolution of lime- and cement-treated specimens by exposing the top surface of the specimens to 0.3% carbon dioxide content. The study examines carbonation’s impact on silty and sandy soils. Specimens treated with 2.5% quicklime, 5% cement, or a mixture of 1% quicklime and 5% cement underwent 28 days of carbonation. The strength obtained was maximum for carbon dioxide–exposed cement-treated soils, followed by combined lime-and-cement-treated soils, and then lime-treated soils. All carbon dioxide–exposed specimens showed comparatively greater strength than the corresponding nonexposed specimens. In addition to calcite deposition, soil suction and cementitious compounds also contributed to this high strength evolution in the carbon dioxide–exposed specimens. Based on physicochemical and pore structure analysis, the combined contribution made by soil suction and calcite precipitation toward strength evolution can be considered almost the same. The significant differences in strength evolution between the carbonated specimens are attributed to the differences in the development of cementitious compounds. This development of cementitious compounds is governed by the soil’s mineralogy and the binders added. The exposure condition of soil specimens during the carbonation reaction defines the soil suction evolution. Therefore, the study highlights the importance of reproducing carbon dioxide content and curing conditions close to the in situ situations to accurately assess the strength evolution of carbonated specimens.