Tailoring the anionic function and the side chains of comb-like superplasticizers to improve their adsorption

Nowadays admixtures and especially superplasticizers are unavoidable components of the concrete formulation. The high fluidizing efficiency of the comb-like superplasticizers must not overshadow their high costs. This study aims to determine the PCE structure parameters which influence their adsorption in order to enhance their resistance to sulfate competitive adsorption and thus minimize their dosage. The PCE adsorption has been studied on calcite and ettringite which are both surfaces representative of early hydrating cement. The effect of the POE side chain length and density and also of the PCE anionic function i.e. carboxylate, dicarboxylate or phosphate on the adsorption has been analyzed. As main result, the modification of the anionic is a good technological way to improve the resistance to sulfate competition. At equivalent charge density, the dicarboxylate polymer is less sensitive to sulfate ion concentrations than the monocarboxylate one, while the phosphate PCE is quite insensitive for the concentrations studied. (C) 2014 Elsevier Ltd. All rights reserved.