Cement-Based Solidi cation/Stabilization of Heavy Metal Contaminated Soils with the Objective of Achieving High Compressive Strength for the Final Matrix

The solidication/stabilization (s/s) of heavy metal contaminated soils using ordinarypontlandite cement (opc) is studied as a hazardous waste treatment technology. the soil-binder ratioof 8% by weight is selected for treatment by setting a justication constraint on the solidied matrix.in order to consider the physical and chemical characteristics of the solidied soil-cement mixtures,compressive strength, toxicity characteristic leaching procedure (tclp), x-ray diraction (xrd)and scanning electron microscopy (sem) are the tests done during this research. the results indicatethat despite an intensive decrease in the compressive strength of solidied soil at early curing ages, thejustication constraint set on the preparation of specimens enhances hydration reactions; and the solidiedmatrix achieves high compressive strength after 7 curing days. the leaching metal concentration inleachates is decreased gradually by aging from 1 to 28 curing days, indicating more metal stabilizationin the form of metal hydroxide precipitation, which presents itself in the developed crystalline phasesof hydrated cement, as observed in xrd patterns or by absorption on csh gel or crystals. leachingmetal concentration in leachates is lower than regulatory limits, so there is no strength concern forenvironmentally safe disposal. heavy metal contamination diverts the cement hydration reactions towardproduction of more subsidiary products, that bear less compressive strength, instead of main hydrationproducts. therefore, the main crystalline phases develop irregularly and coat the aggregates poorly, asobserved in sem micrographs.