Stabilization of Sandy Subgrade Soils with Clay and Crushed Stone

Abstract This study evaluated the improvement of a sandy soil through stabilization with varying clay contents (5%, 10%, 15%, and 20%) and a constant proportion of 5% crushed stone for its application as a subgrade material in an unpaved road in Lima. The research followed an applied approach with an experimental design and a quantitative methodology. Soil samples were collected from three test pits along the road section, and laboratory tests were conducted in accordance with ASTM standards, including Modified Proctor, California Bearing Ratio (CBR), and permeability tests. The results showed that the mixture containing 15% clay and 5% crushed stone provided the best overall performance. Although the maximum dry density reached 1.916 g/cm 3 with 20% clay (a 12.44% increase compared to the natural soil), the 15% clay mixture exhibited the optimal balance between mechanical and hydraulic properties. The CBR increased from 8.6% to 18.5%, representing an improvement of 115.12%, while hydraulic conductivity decreased from 0.00345 cm/s to 0.00049 cm/s, corresponding to a reduction of approximately 85.8%. These improvements significantly enhance the soil’s bearing capacity, compaction efficiency, and drainage characteristics. It is concluded that the combination of 15% clay and 5% crushed stone constitutes an optimal and economically viable solution for stabilizing sandy soils, making it suitable for subgrade applications in urban roads subjected to light to medium traffic conditions