Combination of superplasticizers with hydroxypropyl guar, effect on cement-paste properties

Alexandre Govin (1, 2) , Marie-Claude Bartholin (1, 2) , Wolfram Schmidt (3) , Philippe Grosseau (1, 2)

1 PMMG-ENSMSE - Département Procédés de Mise en oeuvre des Milieux Granulaires
2 LGF-ENSMSE - Laboratoire Georges Friedel
3 BAM Bundesanstalt für Materialforschung u. -prüfung

Viscosity-modifying agent (VMA) are used in several applications of concrete, such as underwater con-crete, Self-Compacting Concrete (SCC) or Self-Levelling Underlayments (SLU) in order to improve thewashout resistance and the stability. The study focuses on the modifications of cement pastes propertiesimplied when a VMA (hydroxypropyl guars or HPG) and a superplasticizer are introduced together. Forreaching this objective, two chemically different polycarboxylate-based superplasticizers (PCE) andtwo HPGs exhibiting different molar substitution ratios (MS_HP), were studied. A method, combining totalorganic carbon and size exclusion chromatography, was developed in order to quantify the adsorption ofthe both admixtures. The adsorption of HPGs appears being significantly lowered by the presence of PCE,while only the adsorption of the less charged PCE is slightly affected by the HPG. As consequence, strongmodifications of the rheological properties of cement pastes were noticed when HPG and PCE are com-bined. The desorption of HPG leads to higher yield stress and residual viscosity than with PCE alone.

Mots clés: Admixture; Rheology; Adsorption; Polymers; Pore solution

Domaines: Matériaux; Génie civil

Alexandre Govin, Marie-Claude Bartholin, Wolfram Schmidt, Philippe Grosseau. Combination of superplasticizers with hydroxypropyl guar, effect on cement-paste properties. Construction and Building Materials, 2019, 215, pp.595-604. ⟨10.1016/j.conbuildmat.2019.04.137⟩. ⟨hal-02149405⟩