Evaluation of the coupled reaction-adsorptionof Ca 2+ ions on ashes from sugar cane bagasse. Kinetic and thermodynamic approaches

The adsorption of Ca2+ ions and the pozzolanic reaction between ashes from sugar cane bagasse (bio-reactant) and Ca(OH)2, are studied in the present paper. The characterization of the bio-reactant by means of XRD, specificsurface Brunauer-Emmett-Teller (BET), thermal differentialanalys is (TDA), thermo-gravimetric analysis and other physical parameters such as pignometric density, porosity,compressibility, form factor and flow velocity, is developed. A four stages mechanism is proposed to describe the pozzolanic reaction according to Zhulaev postulations. Once the reaction takes place, an 85.15% of Ca2+ is converted and the rest remains as adsorbed specie validating a dual adsorption-reaction process. The kinetics of the adsorption process can be described by means of a pseudo-firstorder model and the mechanism is controlled by the film diffusion model. The thermodynamics of the adsorption process fits to the Freundlich isotherm

Evaluation of kaolinite clays of Moa for the production of cement based clinker-calcined clay-limestone (LC3 )

Clay materials from two outcrops of the Moa region were analyzed to determine their potential use as supplementary cementitious material in the production of ternary cements based on limestone-calcined clay. The clays were characterized by atomic absorption spectroscopy (EAA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (ATG). These methods revealed high aluminum in clays, moderate kaolinite content, a disordered structure and the presence of impurities. The solubility of aluminum and silicon in alkali and the compressive strength of LC3 systems is proportional to their content in clay, being higher for the one with higher kaolinite content and greater structural disorder (outcrop D1), although the clay of both outcrops may constitute supplementary cementitious materials in the production of ternary cements based clinker-calcined clay-limestone. The suitable thermal activation range for both clays is between 650 ° C and 850 ° C