Abstract:

The natural pumice powder is used as additives to change the cement-soil properties in order to utilize the abundant natural pumice resources in Inner Mongolia. The mechanical properties of cement-soil can be effectively improved, the durability of cement-soil is significantly enhanced. With the mixing amount of cement 15% as a benchmark, the pumice powder mixing amount is 2%, 4%, 6%, 8%, 10% respectively in the lab. The conservation age is 7 d, 28 d, 60 d, 90 d respectively. The experiments results show that the unconfined compressive strength of cement-soil increases with the mixing amount of the natural pumice powder, it reaches the peak value when the mixing amount is 8%, and there is no increasing after the value with the increasing of the mixing amount of the pumice powder. The strength of the natural pumice powder cement-soil is increasing with the conservation age, which the strength on 90 days is 1.52 to 1.6 times of the strength of on 28 days, the strength increases greatly in the late period. In the conditions of freeze-thaw cycle, the strength increasing trend of the natural pumice powder cement-soil is basically the same as before with the freeze, which the strength of the cement-soil is degraded, but the degree of strength improvement is significantly increased comparing with the soil without pumice powder mixing. The permeability coefficient of the pumice powder cement-soil is decreasing with the conservation age, the impermeability capacity is gradually increased, and particularly the permeability coefficient is decreased rapidly in the first 28 days.

Key words: cement-soil, natural pumice powder, additives, unconfined compressive strength, durabi-lity