Objectives: To find the optimal percentage of eggshell powder which when mixed with expansive soil results in effective foundations for buildings. Methods: In this study, samples from Katreni Kona near Amalapuram, East Godavari District of Andhra Pradesh in the southern part of India was selected to collect the expansive soil which was open excavated at 2.0 m depth beneath the surface of the ground for the study. Eggshell powder (ESP) mixed with expansive soil in different percentages of 5%,

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... , 15% and 20% by dry weight was considered for evaluation. The treated and untreated samples were subjected to Compaction, California bearing ratio (CBR) (soaked and unsoaked) and Unconfined compressive strength (UCS) tests. Findings: The clay content was reduced with an increase in density and liquid limit, subsequently the plastic limit was reduced with the increase of UCS by adding the eggshell powder to the soil. The optimal dried density of the soil was increased from 14.42 kN/m 3 , 14.59 kN/m 3 , 14.71 kN/m 3 , 14.88 kN/m 3 and 14.81 kN/m 3 ,and optimum moisture content was decreased from 28.24 %, 26.42%, 26.09%, 24.48% and 23.02% respectively when 0% to 20% of eggshell powder was mixed with soil. The CBR values were increased until 15% ESP at which the maximum value was attained, and further addition decreased the CBR. Novelty: The engineering nature of expansive soil is extremely enriched with ESP stabilization. The optimum percentage of ESP was 15% when compared with other percentages that were assessed in this investigation. The solidity of soil increased with a reduced number of voids that connect the soil cells, and consistency boundaries of the land were reduced by using ESP. The CBR value with a percentage increase of ESP indicated that the soil is more suitable for foundation.