Adsorption of superplasticizers on hydration products of Portland cement clinker minerals. The process regularities and structure of adsorption layers

Using polymethylenenaphthalenesulfonates and polybenzenesulfonates homologu es of various molecular masses, as well as monomeric sulfonic acids bearing various functional groups as examples, the regularities of the adsorption of chemical additives on silicate and aluminate minerals of cement clinker are studied. It is shown that adsorption of superplasticizers and monomeric sulfonic acids can be described by the Langmuir isotherm. With increasing molecular mass, the adsorption of all additives on both minerals decreases following the inverse Traube's rule, whereas an adsorption activity increas es. The presence of additional functional groups slightly changes the maxim um adsorption in the C(3)A-water system and essentially affects the adsorpt ion on calcium hydrosilicates. Compared to base arylsulfonates, the adsorpt ion activity of polyfunctional additives decreases with respect to calcium hydroaluminates and increases in relation to calcium hydrosilicates. The en ergy of adsorption of additives is higher in the case of hydrosilicates and for both minerals depends slightly on the molecular mass of additives. Var ious approaches are used to analyze the values of parameters of adsorption layer and predominant orientation of molecules within this layer. Monomolec ular layers likely to be formed during adsorption; in the case of the C(3)A the adsorption occurs as a surface phase formation. The regularities obtai ned allow us to estimate the value of adsorption of any additive, with a kn own chemical composition and molecular-mass distribution.