Stabilization of sandy and clayey soils with ornamental stone sludge

This study investigates the effects of ornamental stone processing sludge (SOSP) on the geotechnical behavior of two different types of soils, a high-plasticity clay and a sandy soil. Moving beyond previous literature that focuses only on low SOSP dosages and short curing periods, this investigation reports the strength, resilient, and microstructural behaviors of soil-SOSP mixtures with replacement ratios of 0%, 25%, 50%, 75%, and 100% after a 60-day curing period. Experimental methods included soaked California Bearing Ratio (CBR) and repeated load triaxial Resilient Modulus (MR) tests, combined with pH, SEM, XRD, and XRF analyses. Quantitative results revealed CBR index improvements up to 60% and 50% for the clayey and sandy soils, respectively, while the pure SOSP intrinsic swelling of 3.11% was effectively controlled to values below 1% for all soil-SOSP mixtures. Microstructural mechanisms behind these changes were governed by physical micro-filling effects and targeted cementitious reactions supported by progressive alkalinity over time. The quantitative findings demonstrate that SOSP incorporation into both clayey and sandy soils provides a technically viable and highly sustainable solution for subgrade pavement applications.