This study investigated the progression of deterioration in cement treated surplus soils with cement contents of 1.7, 3.5 and 5.3 % under soaked condition by conducting needle penetration test and measuring calcium ion distribution within soil specimens. It was found that deterioration has progressed throughout the specimen after 336 days soaking in all the cases. From the measurement of calcium ion distribution, it was identified that calcium has leached out from the centre to the surface of the specimens though that distribution did not follow a good correlation with localized strength distribution. It was understood that the progression of deterioration of improved surplus soils with lower cement contents cannot be explained only with the remaining amount of calcium.

In this study, the effect of environmental exposure conditions on the long term mechanical property of surplus soils improved by lime and cement was investigated by conducting unconfined compression tests on the specimens cured under different conditions. As the result of the experiments after about 1 year (336 days) from specimen preparation, the unconfined compressive strengths of the soaked specimens were found to be the smallest, while those of the sealed specimens were the largest. Effect of soaking on the strengths appeared obviously in the cement treated soil, while the effect decreased when the duration of initial sealed curing increased. It was inferred that these differences in the strengths were caused by the changes in physical properties such as degree of saturation, and chemical properties due possibly to the leaching of hydration products during soaked curing.

In this study, the effect of physical and chemical properties on the long term mechanical property of surplus soils improved by lime and cement was investigated by conducting unconfined compression and needle penetration tests on the specimens cured under different conditions. The conditions of curing were set as sealed with plastic wrapping and soaked under pure and acidic water, respectively. As the result of the experiments after about 6 months (168 days) from specimen preparation, effect of soaking on the strengths appeared obviously in the cement treated soil. The unconfined compressive strengths of the soaked specimens were found to be the smallest, while those of the sealed specimens were the largest. It was suggested by the needle penetration resistance that local deterioration progressed gradually from the surface of the soaked specimens. It was inferred that these differences in the strengths between sealed and soaked curing were caused by the changes in physical properties such as degree of saturation, and chemical properties due possibly to the leaching of hydration products during soaked curing.