Evaluation of the effect of eggshell powder on shear strength in clay soils for shallow foundations

Abstract

Clay soils present a challenge in civil engineering due to their high plasticity, significant volumetric changes, and low stiffness, leading to settlement, bulging, and cracking in constructed structures. In Lima, Peru, districts like Ate have alluvial soils composed of highly plastic, low-consistency clays, which compromise the soil's bearing capacity and increase its seismic vulnerability. Furthermore, stabilizers such as cement and lime have high energy costs and CO2 emissions. Therefore, the objective of this research is to determine the effect of eggshell powder (ESP), due to its high CaCO3 content, on the soil's shear strength parameters, evaluating its viability as a sustainable stabilizer for shallow foundations. To this end, Atterberg limits, Proctor compaction, and direct shear tests were performed in the laboratory using samples with 0%, 15%, 25%, and 35% ESP by weight of clay soil. The results showed a reduction in both the plasticity index (from 16% to 8%) and cohesion (from 25.2 kPa to 16.6 kPa), while the angle of internal friction increased from 5.8° to 12.1° and the soil's allowable bearing capacity improved to 146.30 kPa. These findings confirm the potential of ESP as an economical, environmentally friendly, and viable stabilizer for shallow foundations, promoting sustainable geotechnical practices that valorize waste and reduce the carbon footprint of construction.