Chemical resistance of eco-concrete – Experimental approach on Ca-leaching and sulphate attack

The chemical resistance of eco-concrete with high levels (35–65 wt-%) of limestone substitution against Ca-leaching behaviour and sulphate attack was investigated by immersing powdered material in a 10 g L⁻¹ Na₂SO₄ solution. Time-resolved hydrochemical characterisation of the reactive solutions was coupled with chemical, structural and mineralogical characterisation of the experimental solid materials to describe and to quantify alteration phenomena like the dissolution of portlandite and AFm-phases, transformation of C-S-H gel and the precipitation of ettringite, calcite and hydrogarnet. Nucleation and crystal growth dynamics of ettringite are controlled by the availability of Ca, reactive Al, solution pH and potentially the amount of clay minerals and/or superplasticiser used in the eco-concrete material. The experimental approach allows revealing competing reaction pathways and kinetics causing concrete damage in sulphate-loaded environments and to tailor eco-concrete towards an elevated degree of chemical resistance.