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

Abstract

Viscosity-modifying agent (VMA) are used in several applications of concrete, such as underwater concrete, Self-Compacting Concrete (SCC) or Self-Levelling Underlayments (SLU) in order to improve the washout resistance and the stability. The study focuses on the modifications of cement pastes properties implied when a VMA (hydroxypropyl guars or HPG) and a superplasticizer are introduced together. For reaching this objective, two chemically different polycarboxylate-based superplasticizers (PCE) and two HPGs exhibiting different molar substitution ratios (MSHP), were studied. A method, combining total organic carbon and size exclusion chromatography, was developed in order to quantify the adsorption of the 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, strong modifications of the rheological properties of cement pastes were noticed when HPG and PCE are combined. The desorption of HPG leads to higher yield stress and residual viscosity than with PCE alone.

Influence of polycarboxylate superplasticizer, citric acid and their combination on the hydration and workability of calcium sulfoaluminate cement

“…However, the combination of several admixtures in cement paste may cause undesired interactions. Indeed, competitive adsorption between these admixtures on the surface sites of cement particles may occur, which may influence their performances [43][44][45]. When combining PCE with sodium gluconate (NG) or with hydroxyethyl cellulose (HEC), Bessaies-Bey et al [44] found that NG is able to fully desorb the pre-adsorbed PCE while PCE was also able to fully desorb the pre-adsorbed HEC.…”

“…As a result of this competitive adsorption between these admixtures, the yield stress and viscosity of the paste were decreased. In addition, Govin et al [45] highlighted a decrease of the dispersing effectiveness of PCE when combined with hydroxypropyl guar (HPG). The authors demonstrated that the admixtures (PCE and HPG), which were introduced at the same time, competed for adsorption, which explains the decrease of the yield stress of the paste.…”

The Role of Rheological Additives on Fresh and Hardened Properties of Cemented Paste Backfill

“…Bessaies-Bey et al [18] showed that PAM microgels can be adsorbed on cement particles concurrently to establish bridges between them, thereby increasing the macroscopic yield stress. With respect to the increased viscosity and yield stress owing to the viscosity modifying agents, the polycarboxylate superplasticizer (PCE) can be adopted to regulate the workability [19]. Yang et al [16] indicated that the use of superplasticizers in CPB specimens was beneficial in maintaining/improving the workability and strength properties by decreasing water requirements without lowering the fluidity or raising the amount of cement.…”

“…Yang et al [16] indicated that the use of superplasticizers in CPB specimens was beneficial in maintaining/improving the workability and strength properties by decreasing water requirements without lowering the fluidity or raising the amount of cement. Govin et al [19] investigated the effect of PCE and hydroxypropyl guar (HPG) on cement paste properties and showed that the rheological properties of the cement paste were significantly modified when HPG and PCE were combinedly used. Thus, the use of rheological additives should be optimized through a multi-objective approach.…”

Evaluations of All-in-One, Polycarboxylate-Based Superplasticizer with Viscosity Modifying Agents for the Application of Normal-Strength, High-Fluidity Concrete

“…Guar gum improves the water retention of mortar or concrete, adapts the rheological behavior of the cementitious materials, prevents aggregate segregation and improves the workability and homogeneity of cement-based systems. Moreover, the addition of the guar gum slightly increases the strength and reduces the carbonation rate [30,31]. Starches are VMA that alter the properties of a mortar in the fresh state.…”