Amelioration of Soil Expansion Using Calcined Ornamental Stones Hazardous Carbonate Wastes

Serious environmental hazards can be created due to the accumulation of the ornamental stone carbonate wastes in the Shak Al-Thoaban industrial area, Cairo, Egypt. The present study investigates the use of this waste, after calcination, as a soil stabilizing agent. The effect of the calcined carbonate waste (CCW) on the soil swelling, plasticity, and microstructural and mineralogical compositions has been studied. The stabilization was performed using different CCW doses (1.25–12.5%) and various water amounts (20%, 50%, and 80% by the liquid limit of the natural soil). The stabilized samples were cured for different periods (1 h–90 days). The pH, electrical conductivity (EC), and the mineralogical and microstructural characteristics of the stabilized samples were studied with the proceeding of curing time. The Addition of a small amount of the CCW induced significant improvement in the soil swelling and plasticity in the short term. Significant microstructural and mineralogical modifications were achieved after stabilization. A densely packed cement block-like microstructure developed after two weeks of curing. The XRD results indicated the modification of Na-montmorillonite of the natural soil to Ca-montmorillonite in the stabilized one. Formation of hydrocalumite pozzolanic phase was detected starting from the first day of curing up to 90 days. The results of the thermal gravimetric analysis confirmed the development of the Ca hydrate phase in the stabilized soil sample.