Blast furnace slag-modified grouts for in situ stabilization of chromium-contaminated soil

Blast furnace slag-modified grouts were used to stabilize soils contaminated with trivalent and hexavalent chromium. Slag content, grout/soil ratio and water/cementitious material ratio were varied to determine the effects on leachability of chromium, permeability and compressive strength. Slag-modified grouts successfully stabilized Cr(VI)-contaminated soil to give low leachability, thereby allowing omission of the pretreatment stage to reduce Cr(VI) to Cr(III) necessary with lime and ordinary Portland cement stabilization procedures. Leachability of both Cr(III) and Cr(VI) decreased with increasing slag content. The permanence of leach resistance is enhanced by higher slag levels in grout. Compressive strength of grout-treated soil ranges from 6 to 36 MPa and permeability is of the order of 10−11 to 10−7 cm/s, depending on mix proportions. Slag-modified grouts have potential for in situ stabilization of Cr(III)- or Cr(VI)-contaminated landfills.