Browsing by Author "Frias, M."
Now showing 1 - 3 of 3
Results Per Page
Sort Options
Item Effect of ternary cements containing thermally activated paper sludge and fly ash on the texture of C-S-H gel(2012-05) Goñi, S.; Frias, M.; Vegas, I.; García, R.; Vigil De La Villa, R.; GENERALThe texture of the C-S-H gels formed in ternary cement blends containing thermally activated paper sludge (APS), fly ash (FA) from coal combustion and Ordinary Portland Cement (OPC) was studied 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. Two differentiated zones in the PSD of the C-S-H gel at ∼10-20 nm and ∼5 nm were observed. The proportion of such zones depends on the age of hydration and amount of OPC replacement. The incorporation of the additions (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. High correlations were found among these nanostructure characteristics of the C-S-H gel and mechanical strengths.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.Item Sodium sulphate effect on the mineralogy of ternary blended cements elaborated with activated paper sludge and fly ash(2014-03-15) Goñi, S.; Frias, M.; Vegas, I.; García, R.; GENERALThis paper presents an exhaustive study about the identification and evolution of the mineralogical hydrated phases of ternary Portland cements (TPC), containing thermally activated clay waste (paper sludge) and fly ash, exposed to sodium sulphate salt up to 180 days. The repercussion of these mineralogical changes on the microstructure and strength properties is also discussed in this work. The reaction mechanisms of sulphate ion with the paste was carried out through a microstructure study, which included the use of scanning electron microscopy (SEM), porosity and pore-size distribution and X-ray diffraction (XRD). The results showed that ternary Portland cement was stable against sodium sulphate attack at the conditions here studied. The enhancement of flexural strength was a result of the formation of non-expansive ettringite inside the pores and an alkaline activation of the pozzolanic reaction of additions promoted by the ingress of sulphate and secondary related reactions. Accordingly, the microstructure was strongly refined.