Synthesis of Calcium Silicate Hydrate/Polymer Complexes in Nanostructure

Resumo

Hydrated cement paste, composed for the most part by calcium silicate hydrate (C-S-H), is a fragile material with low tensile strength. It is also well known that the addition of silica fume to concrete increases its strength and, consequently, makes it more durable, though also more fragile. To produce more ductile C-S-H, one alternative is the synthesis of C-S-H/polymer nanocomposites or hybrids. The intercalation of organic molecules in C-S-H nanostructure and other cement hydrates can promote radical changes in their properties of all magnitudes, producing cement based materials with greater strength that are also more ductile. The main objective of this work was to study the possibility of intercalation of organic compounds within C-S-H nanostructure, aimed at the synthesis of nanocomposites with atypical properties. Thus, C-S-H gels were synthesized with various Ca/Si molar ratios using two synthesis methods (precipitation synthesis and pozzolanic synthesis), with or without the presence of polymers. The effect of poly-diallyldimethylammonium chloride (PDC - used as the basis for superplasticizers for concrete) was evaluated, indicated by the literature as capable of intercalating between the C-S-H lamellae [1-5], and copolymer poly(ethylene-co-vinyl acetate) (EVA), indicated by the literature as a modifier of C-S-H morphology [6,7]. The PDC polymer promoted alterations in C-S-H synthesis nanostructural bonding, influencing the interlayer distance and the type of bonding in the dreierketten and wollastonite chains. However, this modification was partial and occurred at rates that require further investigation, since they are probably influenced by the complex characteristics of formation, both by the type of bond and by the irregular and minimally crystalline formation of C-S-H.