Browsing by Keyword "Pore-size distribution"
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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 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.