Using fly ash and volcanic tuff along with lime for stabilizing high plasticity clay soil

Purpose: The study aims to investigate the impact of using fly ash, volcanic tuff, and lime in the chemical stabilization of highly plastic clay. Theory and Methods: In this study, fly ash and volcanic tuff were mixed separately with high-plasticity clay, and experiments were carried out. Then, in addition to these additives, 6% lime was added, and the same experiments were repeated. The study investigated the impact of additives on various properties of clay, including consistency limits, maximum dry unit weight, optimum water content, and unconfined compressive strength. ASTM D1140, ASTM D422, ASTM D854, ASTM D698, ASTM D4318, and ASTM D2166/D2166M-16 standards were applied in the experiments. The additive ratios that gave the highest unconfined compressive strength were selected, and samples were prepared for these ratios. The samples were dry-cured for 7, 14, 21, 90, and 120 days and then unconfined pressure tests were performed on the samples. Results: Clay + fly ash samples were created by mixing fly ash with clay at weight ratios of 0%, 5%, 10%, 15%, 20%, 25% and 30%. Clay + volcanic tuff samples were also prepared by mixing volcanic tuff with clay at weight ratios of 0%, 5%, 10%, 15%, and 25%. Then, the experiments were repeated for the same fly ash and volcanic tuff ratios, while keeping the optimal lime ratio of 6% constant. The addition of fly ash reduced the liquid limit, and plasticity index while increasing the unconfined compressive strength. Similarly, the addition of volcanic tuff resulted in reduced liquid limit and plasticity index of the clay, along with increased unconfined compressive strength. Adding 6% lime to these additives improved the engineering properties of the mixtures more effectively. For each additive, the ratios that yielded the highest unconfined compressive strength were identified as Clay+ 15% fly ash, Clay+10% volcanic tuff, Clay+15% fly ash+6% lime, and Clay+10% volcanic tuff+6% lime. An increase in the unconfined compressive strength of the samples was observed with increasing curing time (7, 14, 21, 90, and 120 days). Conclusion: It has been demonstrated that fly ash and volcanic tuff can be utilized for stabilizing high- plasticity clay soil. It has also been found that adding lime at the optimal rate enhances the success of stabilizing these materials.