Effects of a water-retaining agent on the rheological behaviour of a single-coat render mortar

Influence of hydroxypropylguars on rheological behavior of cement-based mortars

“…In contrast, Cappellari et al [17] obtained a reduction in yield stress of mortar with increasing dosage of hydroxyethyl methyl cellulose. The results of Paiva et al [15] and Bouras et al [18] show an initial decrease followed by an increase in mortar yield stress when the dosage of hydroxypropyl methyl cellulose and starch ether, respectively, increases. In addition, these trends can be amplified or modified when several polysaccharidic admixtures are blended, due to synergic effect and formation of interpolymer complexes [19].…”

“…However, according to several authors, polysaccharides lead to an increase in the entrained air amount [15,17], highlighted by a rise in the total porosity from 15 to 50% and a drop of the mortar density [35,[52][53][54], to steric hindrance induced by their adsorption on cement grains [16] and repulsive depletion forces induced by polymers dissolved in pore solution [16]. All these factors tend to decrease impact of Van der Waals attractive forces and thus yield stress.…”

“…The use of VEAs allows overcoming this problem by enhancing the sedimentation resistance while maintaining high fluidity [8][9][10][11][12][13]. The incorporation of VEA in shotcrete or render mortar is also very useful to ensure sagging resistance for thick application on vertical support, and allows sufficient fluidity for normal pumpability [10,[14][15][16][17] by supplying shear thinning rheological behavior. Thus polysaccharides provide high yield stress and apparent viscosity at low shear rate but low resistance to flow at high shear rate [7].…”

“…Among the polysaccharidic VEAs, microbial-source polysaccharides such as welan gum [11][12][13]20,21] and cellulose ethers [14][15][16][17]22] are the most widely used and studied. Nevertheless, the hydroxypropylguar (HPG) are now well-established in the construction industry as water retention agent for mortars [23].…”

Influência do uso de aditivo retentor de água à base de éter de celulose nas propriedades das argamassas de assentamento em alvenaria estrutural de blocos de concreto

“…Também conhecidos como aditivos promotores de viscosidade, os aditivos retentores de água são em sua maioria à base de éter de celulose, sendo os mais comumente empregados na confecção de argamassas o hidroxipropil-metilcelulose (HPMC) e o hidroxietil-metilcelulose (HEMC) (PAIVA et al, 2006). Polímeros à base de éter de celulose são materiais orgânicos derivados da celulose e solúveis em água, que apresentam como propriedade principal a grande capacidade de reter água (PAIVA et al, 2009).…”