Long term strength development of lime stabilized soils

Abstract

To study the long term strength development of lime stabilized soils, samples were prepared using different types of soil and varying lime content and compaction condition. The unconfined compression tests were carried out on stabilized samples at 7, 28, 90, 180 and 360 days. The unconfined compressive strength of stabilized soil was also determined after soaking the specimen in water. Three types of soil, collected from Dhaka and adjacent areas, were used for the research work. Two soils were MLlCL type and the other one was CL type according to Unified Soil Classification System. Slaked lime was used as a stabilizer. The unconfined compressive strength of the soil was increased when it was stabilized with lime. The gain in strength was found to depend on a number of factors, such as lime content, soil type, curing time, mellowing time, compaction energy etc. For a particular curing period soil stabilized with higher percentages of lime showed higher compressive strength.

The CL type soil was found more suitable for lime stabilization. It attained reasonably high strength with small quantity of lime. The unconfined compressive strength of lime treated CL type soil was higher than MLlCL type soil for a given lime content and curing period. Soil containing organic matters (about 2%) need high lime content and longer curing period for stabilization. The strength of lime stabilized soil continued to increase with curing period. The rate of gain in strength was not constant with time. Initially the rate of gain in strength was high, after that the rate decreased. The soils stabilized with lower amount (3%) of lime did not show increase of strength after 180 days of curing period. But with higher amount of lime (5%, 7%), the strength increased beyond 180 days. The 360-day strength of the lime stabilized soil was appreciably higher than the 28-day strength. This was pronounced when stabilized with higher percentages of lime. The decrease in strength due to compaction delay was seen to depend on soil type. The decrease in strength was less in CL type soil than that of MLlCL type soil. The reduction in 28-day strength is about 15% for 24 hours (1 day) delay in compaction. Whereas for 336 hours (14 days) delay in compaction, the reduction in strength was approximately 50% when CL type soil was stabilized with 3% lime. The decrease in strength due to retempering was found to be similar to that of compaction delay. There was a small 1055 of strength of lime stabilized soil when they were immersed in water, for 7 days. For CL type soil, the ratio of soaked to unsoaked unconfined compressive strength was observed to vary between 0.71 to 0.85 depending on lime content and curing period.