Environmental assessment of the behavior of a BOF steel slag used in road construction : the PRECODD-ECLAIR research program

International audienceSteel production generate great amounts of by-products as steel slags. The use of Basic Oxygen Furnace slags (BOF slags) has been restrained due to insufficient volume stability, and due to the lack of environmental regulations. The purpose of the PRECODD-ECLAIR research program is to develop a behavior model based on a multi-scale physico-chemical, mechanical, hydrodynamic and ecotoxicological characterizations of a BOF slag used in a public works scenario. This paper aims at presenting the overall ECLAIR research program, the equipped experimental platform constructed using a BOF steel slag, and the first results of the slag characterization

Microstructural investigations on plasticity of lime-treated soils

The surface charge distribution of clay particles governs the interparticle forces and their arrangement in clay-water systems. The plasticity properties are the consequences of the interaction at the microscopic scale, even if they are traditionally linked to the mechanical properties of fine-grained soils. In the paper, the plasticity modifications induced by the addition of lime were experimentally investigated for two different clays (namely kaolinite and bentonite) in order to gain microstructural insights of the mechanisms affecting their plastic behavior as a function of the lime content and curing time. Zeta potential and dynamic light scattering measurements, as well as thermogravimetric analyses, highlighted the mechanisms responsible for the plastic changes at a small scale. The increase of the interparticle attraction forces due to the addition of lime increased the liquid and plastic limits of kaolinite in the short term, without significant changes in the long term due to the low reactivity of the clay in terms of pozzolanic reactions. The addition of lime to bentonite resulted in a decrease of interparticle repulsion double layer interactions. Rearrangement of the clay particles determined a reduction of the liquid limit and an increase of the plastic limit of the treated clays in the very short term. Precipitation of the bonding compounds due to pozzolanic reactions increased both the liquid and plastic limits over the time