ABSTRACT:Swelling soils which are problematic in terms of geotechnics should be determined in preliminary works a n d appropriate cautions should be taken. The most frequently used method among the cautions to be taken is to stabilize soil with in-situ operations. One of the most widely used stabilization methods is lime column technique. Before stabilizing a swelling soil with lime column technique, it is investigated if the lime column works for the soil. This is done by creating a small-scale model of the land in the laboratory. The created models are left for a specific curing time to ensure the stabilization. Determination of the appropriate curing time is important for the performance of lime column. The aim of this study is to determine the curing time for the laboratory models, which are designed for investigating lime column performance, with an easy a n d economic method. The method is based on measuring the ion migration distance by using phenolphthalein which is an acid base indicator. In the scope of the study, a small scale laboratory model was designed for a Na-bentonite clay. The ion migration distance from the lime column in the model was measured by using phenolphthalein in various curing times a n d the measurements were stopped when the ion migration distance reached a constant value. The time in which the ion migration distance started not to change was taken as the cure time. The results obtained in this study showed that phenolphthalein can be a useful tool for determination of curing time in the laboratory applications of lime column.