Browsing by Keyword "Fly ash"
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Item Aging and durability of ternary cements containing fly ash and activated paper sludge(2014-02-15) Vegas, I.; Gaitero, J. J.; Urreta, J.; García, R.; Frías, M.; GENERAL; Tecnalia Research & Innovation; ECOEFICIENCIA DE PRODUCTOS DE CONSTRUCCIÓN; Infraestructuras y Servicios CorporativosThis research work deals with durability aspects of ternary cements containing 79 wt.% ordinary Portland cement (CEM I), 10.5 wt.% coal fly ash and 10.5 wt.% thermally activated paper sludge. Aging tests were performed to study the resistance of the new ternary cement matrixes to the following aggressive exposure conditions: accelerated freeze/thaw cycles, marine environment and Spanish plateau climate conditions. Ternary cements revealed a high resistance to accelerated freeze/thaw cycles. In addition, after 18 months of exposure, they exhibited enhanced performance under marine conditions and similar resistance to Spanish plateau's climate, compared to ordinary Portland cement.Item Belite cements: Modifications of calcium silicate hydrate (C-S-H) gel by alkaline hydrothermal activation(2009-03) Guerrero, Ana; Goñi, Sara; Dolado, Jorje S.; Tecnalia Research & InnovationThe C-S-H gel of two types of fly ash belite cements (FABC) are studied at a nanwscale (1 to 100 nm [39.4 to 3940 nin.]) by means of the specific surface area and pore-size distribution, which were measured by the sorption isotherms of nitrogen gas and the BET method. The two belite cements were fabricated by the hydrothermal-calcination route of Class C fly ash in NaOH 1M solution (FABC-2-N) and demineralized water (FABC-2-W). Two differentiated zones in the pore-size distribution of the C-S-H gel at ∼12 and ∼3 nm (∼473 and ∼118 nin.) with different influences in the mechanical strength were produced. The proportion of both zones depends on the age of hydration and type of belite cement. At early ages, the C-S-H gel of FABC-2-N develops both zones in a greater proportion than those of FABC-2-W. At later ages, the behavior is opposite: the C-S-H gel ofFABC-2-W develops high proportion of pores of 3 nm (118 nin.) of diameter. Important quantitative correlations were found among these nanostructure characteristics of the C-S-H gel and macrostructural engineering property. copyrightItem The combined effect of activated paper sludge and fly ash on the ternary cement properties(European Conference on Composite Materials, ECCM, 2012) Frías, M.; Vegas, I.; Goñi, S.; García, R.; Vigil De La Villa, R.; GENERALThis paper presents the main scientific and technical aspects of a pozzolans blend (activated paper sludge (APS) and fly ash (FA)) and its influence on the ternary cement behaviour. Due to the high pozzolanic activity of binary addition, the blended cements (6 and 21%) shows a different behaviour with respect to the control one. The normal consistency water content (up to 10%) and the initial setting decrease in comparison with the control paste. Finally, the compressive strength slightly decreased in the blended cements elaborated with 21% of the pozzolan blend, although the decrease in their strength is lower than the total percentage of cement that is replaced. At 90 days, a recovery of mechanical resistance is observed in the ternary cements as a consequence of the activity developed by the fly ash.Item Forced Aging and Ionic Mobility of Ternary Cements Exposed to Aggressive Saline Marine Environments and Cryoclastic Processes(2015-07-27) Giménez, Rosario García; De La Villa, Raquel Vigil; Rubio, Virginia; Vegas, Iñígo; Frías, Moisés; GENERALAbstract The most common supplementary cementitious materials used in concrete, in addition to Portland cement, are fly ash and silica fume; metakaolin, produced by controlled thermal treatment of kaolin, is also used in cementitious composites on account of its pozzolanic properties. This study forms part of an extensive research into the degradation of uncommercialized pozzolanic ternary Portland cement (TPC) exposed to different saline marine environments and cryoclastic processes. In marine environments, CSH gels from ordinary Portland cement fill the gaps between the grains and cover the surfaces. However, the porosity of ternary Portland cement is notably higher and permits the retention of ions. Cracking as a consequence of cryoclastic processes is found in the CSH gels and ettringite of ordinary Portland cement in continental climates. However, when ternary Portland cement is studied under similar conditions, the cracks are partially sealed by the gels without further rupturing due to the aforementioned processes.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.