Thermal evidences of the interaction between plasticizers and Ca salts in cement

The interactions between an organic polymer with plasticizing activity and a model surface (CaCO₃), with a surface activity similar to the cement one, have been analysed by volumetric analysis and thermal analysis: TG/DTG and DSC. The synthesized polymer has a negative link site (carboxylate) that is able to interact with the substrate and a long ethylene oxide chain that contribute to the dispersing activity. The pattern of the adsorption isotherm suggests the occurring of a step like adsorption, initially characterised by a coil conformation of PEO chain followed by a more PEO strained, linear, conformation as the amount of polymer increases. The polymer adsorption appears to modify the crystalline phase and morphology of the CaCO₃ surface as the thermal analysis puts in evidence through the CaCO₃ decomposition temperature shifts. SEM analysis confirms the morphology changes induced by polymer adsorption.