Interaction Between Superplasticizers and Calcium Aluminate Hydrates

Abstract

Sodium lignosulfonate and naphthalene and melamine sulfonate formaldehyde condensates, dissolved in lime water, are adsorbed on C4AHU and C&i6. When dissolved in dimethylsulfoxide the same admixtures are adsorbed on CsAHIJ but, apparently, not on C3AHa. The adsorption isotherms of the two polycondensates are very similar but different from those of lignosulfonate. This fact can be attributed to the considerable structural difference between the synthetic admixtures and the lignine derivative. The particle zeta potential is modified by the presence of the admixtures, minimum additions of which are enough to bring the zeta potential to negative constant values. Nevertheless, the values of the potential cannot be correlated with the viscosity of the aluminate hydrate pastes, since the viscosity first increases and then decreases as the admixture increases. This behavior can be explained by a bridging effect among the particles, which overcomes the repulsive effect due to zeta potential.

Use of lignin-based products in concrete

“…Adsorption isotherms in the aqueous medium are shown at the right-hand side of Figure 11. The zeta-potential was found to decrease linearly as the adsorption increased and stabilized to a constant value when the isotherm reached values approaching the maximum adsorption [20]. The left-hand side of Figure 11 shows the zeta-potential measurements corresponding to the amount of adsorbed admixture.…”

“…The dispersing action of such admixtures is explained in terms of lowering of zeta-potential, that results upon adsorption of the admixture in the cement paste phase [ 11,19,20]. The dispersing action of such admixtures is explained in terms of lowering of zeta-potential, that results upon adsorption of the admixture in the cement paste phase [ 11,19,20].…”

“…The zeta-potential of the cement-water system without any additives is about -8 millivolt (mV) [19]. Exhaustive investigations on the effects of lignosulphonate-based admixtures and superplasticizers on the adsorption characteristics and zeta-potential on the cement as well as various cement minerals have been reported [20,. Exhaustive investigations on the effects of lignosulphonate-based admixtures and superplasticizers on the adsorption characteristics and zeta-potential on the cement as well as various cement minerals have been reported [20,.…”

“…Lignosulphonate salts play an important role in set retardation and both sugar-free calcium-and sodium-lignosulphonates were found to retard the hydration of C,A as efficiently as commercial lignosulphonates [24]. Massazza and C,A dispersed in solution containing sodium lignosulphonate [20]. Massazza and C,A dispersed in solution containing sodium lignosulphonate [20].…”

Chemical Admixtures of Highway Concrete: Fundamental Research and a Guide to Usage, Part II - Quantitative Analysis of Interactions between Portland Cements and Superplasticizers

“…Massazza et al [42,43] investigated effects of the superplasticizer on C,A hydration. He found that both naphthalene sulfonate and lignosulfonate slowed down the rate of ettringite formation.…”