Thermal Evidences of the Interaction Between Plastcizers 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.