Laboratory Studies on Stabilization of an Expansive Soil by Lime Precipitation Technique

Lime stabilization prevails to be the most widely adopted in situ stabilization method for controlling the swell-shrink potentials of expansive soils despite construction difficulties and its ineffectiveness in certain conditions. In addition to the in situ stabilization methods presently practiced, it is theoretically possible to facilitate in situ precipitation of lime in soil by successive permeation of calcium chloride (${\mathrm{CaCl}}_2$) and sodium hydroxide (NaOH) solutions into the expansive soil. In this laboratory investigation, an attempt is made to study the precipitation of lime in soil by successive mixing of ${\mathrm{CaCl}}_2$ and NaOH solutions with the expansive soil in two different sequences. Experimental results indicated that in situ precipitation of lime in soil by sequential mixing of ${\mathrm{CaCl}}_2$ and NaOH solutions with expansive soil developed strong lime-modification and soil-lime pozzolanic reactions. The lime-modification reactions together with the poorly developed cementation products controlled the swelling potential, reduced the plasticity index, and increased the unconfined compressive strength of the expansive clay cured for 24 h. Comparatively, both lime-modification reactions and well-developed crystalline cementation products (formed by lime-soil pozzolanic reactions) contributed to the marked increase in the unconfined compressive strength of the expansive soil that was cured for 7–21 days. Results also show that the sequential mixing of expansive soil with ${\mathrm{CaCl}}_2$ solution followed by NaOH solution is more effective than mixing expansive soil with NaOH solution followed by ${\mathrm{CaCl}}_2$ solution.