Interactions between hydrated cement paste and organic acids: Thermodynamic data and speciation modeling

Laurent de Windt (1) , Alexandra Bertron (2) , S. Larreur-Cayol (2) , Gilles Escadeillas (2)

1 GEOSCIENCES - Centre de Géosciences
2 LMDC - Laboratoire Matériaux et Durabilité des constructions

Interactions of short-chain organic acids with hydrated cement phases affect structure durability in the agro-food and nuclear waste industries but can also be used to modify cement properties. Most previous studies have been experimental, performed at fixed concentrations and pH, without quantitatively discriminating among polyacidity effects, or complexation and salt precipitation processes. This paper addresses such issues by thermodynamic equilibrium calculations for acetic, citric, oxalic, succinic acids and a simplified hydrated CEM-I. The thermodynamic constants collected from the literature allow the speciation to be modelled over a wide range of pH and concentrations. Citric and oxalic had a stronger chelating effect than acetic acid, while succinic acid was intermediate. Similarly, Ca-citrate and Ca-oxalate salts were more insoluble than Ca-acetate and Ca-succinate salts. Regarding aluminium complexation, hydroxyls, sulphates, and acid competition was highlighted. The exploration of acid mixtures showed the preponderant effect of oxalate and citrate over acetate and succinate.

Domaines: Géochimie

Laurent de Windt, Alexandra Bertron, S. Larreur-Cayol, Gilles Escadeillas. Interactions between hydrated cement paste and organic acids: Thermodynamic data and speciation modeling. Cement and Concrete Research, 2015, 69, pp.25-36. ⟨hal-01108814⟩