Influence of anions on the geotechnical properties of soils treated with hydraulic binders: Individual and coupling effects

• A soil is submitted to an addition of SO42−, Cl−, NO3− or PO43− before treatment.
• The influence of SO42− alone or co-added with another anion is evaluated.
• Anions influence is estimated through swelling and indirect tensile strength.
• When co-added to other anions, disturbances appear at weaker SO42− contents.
• Co-addition induces more important disturbances than single addition of SO42−.

The treatment of soils with hydraulic binders improves their physical and mechanical characteristics, allowing the soils to be reused in several geotechnical applications such as road construction. The aim of this research study is to assess the influence of sulfate, chloride, nitrate and phosphate ions, introduced as CaSO4·2H2O, NaCl, NH4NO3 and KH2PO4, on the physical and mechanical properties of a treated soil under accelerated curing conditions. Then, the influence of sulfate ions is determined in the presence of another anion.Regarding the influence of each anion on the soil considered, only phosphate ions have a deleterious effect on the stabilization at concentrations between 3 and 10 g kg−1 of dry soil. The sulfate ions induce an important volumetric swelling at 10 g kg−1.However, the combination of one anion with sulfate ion induces important disturbances on both volumetric swelling and indirect tensile strength: these interactions must be taken into account in the determination of the stabilization of disruptive parameters.