The effect of carbonation on a one-year atmospherically exposed lime-treated soi l structu r e is investigated. The investigation involves analyzing the chemical characteristics and pore-structu r e modifications of several specimens sampled up to 12 cm depth perpendicular to the surface. On comparing the analysis with untreated and lime-treated core-sampled specimens, carbonation is found to have occurred on specimens sampled up to 4.2 cm depth perpendicular to the surface. The decrease in soi l pH to a value 9 or lower than that and the presence of carbonates confirmed the carbonation effect. At the pore-structure level , carbonation mechanism is found to increase macropores of diameter 20000-100000 angstrom, which is missing in the non-carbonated specimens and even greater than the one found at untreated soil. Such an observation confirmed the loss of cementitious compounds due to carbonation, thus, converting the mesopores developed due to lime treatment to macropores of larger pore diameter.