Impact of hydroxypropylguars on the early age hydration of Portland cement

Abstract

Hydroxypropylguars (HPG) are used as admixtures in factory-made mortars. These molecules present water retention properties comparable to those obtained with commonly used cellulosic water-retaining agent. The influence of HPG on cement hydration was investigated in order to improve understanding on the delayed effect induced by polysaccharides. Hydration kinetics were characterized by means of conductivity and isothermal calorimetry measurements. The influence of polymer concentration and predissolution was studied. A weak influence of HPG on the germination of hydrates was observed. In contrast, HPG induced a significant decrease in the hydrates growth rate. Strong effects of the polymer concentration and predissolution were noticed too. From these results, we supported the hypothesis that HPG adsorption on hydrated phases via polar interactions should be responsible for the delayed effect observed.

Modification of water retention and rheological properties of fresh state cement-based mortars by guar gum derivatives

“…5(a)). This tendency is consistent with previous studies conducted on HPGs and cellulose ethers (CE) in cementitious materials [15,20]. Fig.…”

Influence of hydroxypropylguars on rheological behavior of cement-based mortars

“…In literature, an increase in the DS conducts to a decrease in zero-shear rate viscosity. However, in the same time, polymer adsorption on cement phases is also reduced [29]. Consequently, the effect of substitution degree on viscosity is compensated by the effect of adsorption ability, leading to comparable viscosities.…”

“…The sample thus exhibits higher viscosity at low shear rate and higher yield stress. Moreover, polysaccharides such as HPG and HPMC are able to adsorb on cement grains [29,48]. Since polysaccharides exhibit long chains, the same molecule can adsorb on separate cement particles and draw them together.…”

“…The efficiency of HPG as good water retention agent has been shown by several authors [17,[29][30][31] but studies about their effect on rheological properties are very scarce. Izaguirre et al [32] have worked with aerial lime-based mortars and Cappellari et al [17] have characterized only one HPG.…”

Use of ultrasonic degradation to study the molecular weight influence of polymeric admixtures for mortars

“…On the other hand, hydropropylguar were tested. In 2004, these guar gum derivatives were presented by Plank as promising new class of water-retaining agent [30] because of high water retention capacity [31][32][33] and a low pollution process of manufacturing [34]. HPG use is now well-established in industrial construction chemistry.…”