Efeito combinado da temperatura e do tipo de álcali na solidificação do sistema CaO – SiO2 – M2O – H2O

Abstract

The concrete is one of the most used materials by humankind and it is associated with the degree of development of the society. It is classed as a composite material, i.e., a combination of at least two chemically and mechanically dissimilar materials possessing a definite interface, combining the constituents’ own properties. The concrete based on Portland cement is a composite obtained by mixing hydraulic cement, agregates and water in order to give way for chemical reactions during the setting of cement (hardening). Once hydrated, this material will introduce reaction products such as C-S-H (Calcium silicate hydrate), CH (Calcium Hydroxide), aluminates and ferrite-based compounds, besides non-hydrataed cement particles. Among the gamma of hydrated products C-S-H stands up as one of the most impontant for it render excellent mechanical properties to the final product. The C-S-H is semicrystalline material having a lamellar structure and its crystal structure has not been fully resolved yet, not even by the current morphological characterization techniques. It acts as a glue in the hydrated Portland cement paste. The work herein aimed at the synthesis and characterization C-S-H gels through aqueous route using as precursors silica and calcium reach sources. Solution of 1M of the precursors were used in the mixtures; the molar ratio between silicate and portlandite in all procedures were kept constant at 2:1. The reactions were carried out at temperatures of 40oC and 60oC. The reaction products were assessed by means of X-ray fluorescence, X-ray Diffraction, Thermal Analysis, Infrared Spectroscopy (FTIR) and scanning Electron Microscopy (SEM). The results show that the C-S-H gel product was successfully obtained and it is typical of C-S-H (I). The relation Ca/Si was found to be between 0.9 and 1.39, which is similar to that one found in torbemorite structure. The morphological feature did not change with the reaction temperature. Based on the results previously shown, the aqueous route for synthesis of calcium silicate hydrate introduces a novel and important way of understanding the mechanism of formation of this hydrate product of Portland cement.