Browsing by Author "De La Villa, R. Vigil"
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Item Decalcification of activated paper sludge - Fly ash-Portland cement blended pastes in pure water(2013-07) Goñi, S.; Frías, M.; De La Villa, R. Vigil; Vegas, I.; GENERALDecalcification in pure water of ternary Portland cement (TPC) pastes, containing thermally activated paper sludge and fly ash, has been evaluated from the leaching of Ca2+ in pure water at the temperature of 20 C during 90 days. Monitoring of calcium loss showed that the leaching kinetics are controlled by diffusion. The degradation of the material over time is estimated from the calcium effective diffusivity. A similar study of plain ordinary Portland cement (OPC) pastes was carried out for comparison. The results showed lower effective diffusion coefficients of calcium in the case of the TPC pastes. This behaviour is related to its microstructure, which is denser than that of OPC as a result of the pozzolanic activity of both additions.Item Quantitative correlations among textural characteristics of C-S-H gel and mechanical properties: Case of ternary Portland cements containing activated paper sludge and fly ash(2012-09) Goñi, S.; Frias, M.; Vegas, I.; García, R.; De La Villa, R. Vigil; GENERALThe hydraulic activity of ternary Portland cements containing different proportions of commercial thermally activated paper sludge (APS(I)) and fly ash (FA) from coal combustion was evaluated from the textural characterization of the C-S-H gels formed during hydration. The study was accomplished by means of the specific surface area (SSA) and pore-size distribution (PSD), which were measured by the sorption isotherms of nitrogen gas and the BET method. The microstructure was characterized by scanning electron microscopy (SEM). The incorporation of such admixtures (APS and FA) clearly revealed an increase in both porosity and SSA. This effect decreased with the progress of hydration, together with a refinement of the nano-porous structure of C-S-H. In addition, high correlations were found between nano-structural characteristics of the C-S-H gel and mechanical compressive strengths.