Effect of molecular weight of sulphonated acetone-formaldehyde condensate on its adsorption and dispersion properties in cementitious system

This article studied the effect of molecular weight of sulphonated acetone-formaldehyde condensate (SAF) on the adsorption and dispersion properties in cementitious system. SAF was separated into four different molecular weight fractions using ultrafiltration membranes. The adsorption behaviors were investigated by measuring the adsorption amount, zeta potential, and thickness of the adsorbed films obtained from various SAF fractions. Results show that the SAF fraction with a higher molecular weight has larger adsorption amount, higher absolute value of zeta potential, and thicker adsorbed film, which induces better dispersibility of the corresponding cement paste. An adsorption model of SAF on cement surface is presented. The SAF fraction with a higher molecular weight is more likely to twist and be adsorbed on cement particles through “loop and tail” adsorption. On the contrary, SAF fraction with a lower molecular weight tends to be adsorbed on cement particles through “flat train” adsorption.