Effect of Curing Time and Bentonite Content on the Quantitative Evaluation of Engineering Behavior of Cement Treated Clayey Mixtures Under Soaked Conditions
B.Sc., M.Sc., Ph.D., F.G.S., Lecturer, Laboratory of Soil Mechanics and Foundation Engineering,Geotechnical Engineering Division, Department of Civil Engineering, Aristotle University of Thessaloniki, Thesssaloniki, Greece
Cement - stabilization in clayey soils results from two distinct chemical processes, cation exchange and flocculation. These processes are associated with the potential bonds developed between cement and soil grains.
The efficacy of cement - stabilization method is related with the composition of soils and the stabilization parameters such as percentage of cement, compaction and curing time. The curing time (time of reactions provided by cation exchange and flocculation processes) plays a vital role for the development of efficient cement stabilization. Strength and durability loss of cement stabilized clay soils after soaking in water is attributed to water absorbing capacity of dominant clay mineral (e.g. montmorillonite).
The swelling clays such as bentonite soaked in water, due to environmental conditions, result to volume increase causing macro and micro-fracturing in cement stabilized soil mass. These fractures accelerate water penetration and establish the initiation a slaking which causes strength and durability loss. For these reasons, in this research work, the influence of bentonite content was evaluated on strength and slaking of clay mixtures prepared with constant percentage of kaolin and different proportions of bentonite. Also the rate of strength and durability gained during curing and soaking in water, of cement stabilized active bentonite-sand mixtures, was evaluated in terms of parameters Strength Development Index (SDI) and Slaking Development Index (SLDI) in relation to cement content. By relating strength or slaking values developed during curing time with the corresponding strength or slaking values developed during soaking time, the slope parameter k of these linear relationships was evaluated for cement stabilized active bentonite-sand mixtures.
Finally it was found that strength and durability values were increased with prolonged increase of curing and soaking time, increase of cement content and decrease portion of active clay mineral.
Keywords: curing, soaking, strength, slaking, bentonite, cement stabilization.
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