Polymeric admixtures effects on calcium carbonate crystallization: relevance to cement industries and biomineralization

In the cement industries the use of plasticizer additives, referred to as admixtures, to increase the material workability is of growing interest. Polymeric admixtures are sulfonate or carboxylate polyelectrolytes, the last had been recently also grafted with methoxy poly( ethylene glycol) chains. Their structure and chemical composition recall the acidic macromolecules hosted by several mineralized tissues. The mechanism of action of the polymeric admixtures on cement hydration and carbonation is still poorly understood. Here, we report a study on the variations in the calcium carbonate morphology and polymorphism induced by the presence of commercial polymeric admixtures, since calcium carbonate is one of the products of cement carbonation. We found that the conformation of the polymeric admixtures, the kind of charged functional groups and the presence of grafted chains are the crucial parameters for the specific control of the calcite crystals size and morphology. The formation of crystalline faces already observed in biogenic calcites, as function of the presence of carboxylate or sulfonate groups in the polymeric chain, was obtained. This work evidences an analogy between the polymeric admixtures and the acid macromolecules with respect to calcium carbonate crystallization and the gained information are of interest both for the cement industries and to the understanding of the biomineralization processes.