Abstract: The high liquid limit laterite soil frequently needs to be improved by adding lime or cement due to its moisture susceptible property, while it is used to construct subgrade. However, it’s difficult to uniformly mix ash and soil for the aggregate phenomenon of laterite soil; that would influence on the expected stabilization effects finally. California bearing ratio (CBR) tests are conducted on different sizes aggregation soil specimens of laterite soil and lime stabilized soil. The results show that, the dry density of soil mass increases first and then decreases with the increase of aggregate soil diameter, and the diameter corresponding to the maximum dry density is in 0.2-5 mm range for both laterite soil and lime stabilized soil; and the diameters of laterite soil and lime soil corresponding to the largest CBR values are in 5-10 mm and 2-5 mm range, respectively. The absorption and inflation rate decrease first and then increase with the increasing of aggregate soil size of them. The swelling percent of them are at minimum stage in the diameter range of 2-10 mm. Lime could reduce the expansive of the laterite soil significantly; when the aggregate soil diameter is less than 5 mm. It’s very important to control the size of soil mass strictly in the site construction, so as to ensure the soil strength and moisture don’t fluctuate.

Key words: aggregate soil, size effect, laterite soil, California bearing ratio