Comportamiento de los cementos Pórtland con puzolanas silícicas frente al ataque del yeso, determinado mediante el Método ASTM C 452-68

Abstract

For this study, ASTM C 452-68 testing was conducted for two years on 54 POZC-silica fume (SF) or diatomites (D and N) (=Z pozzolans), were tested for 2 years, by ASTM C 452-68 method, having determined to their specimens their Vcl(=ΔL(%)/day) . The results have borne out that the pozzolanic reactions from SiO 2 r-of these Z pozzolans, in a sulfatic environment, had prevailed sooner (with D and N) or later (with SF) over the sulfatic hydration of their POZC, reaching completion in the first 28 days. Therefore, after positive result is obtained in the Frattini test, as well as in other equivalent tests standardized, the ASTM C 452-68 test can be validly used to differentiate 28-day POZC-Z pozzolan or with any other from natural or artificial origin, which may or may not give rise to the development of low, moderate or high SR. The only requisite would be to establish suitable standard physical-chemical requirements and specifications.. Keywords: gypsum attack; portland cements; silica fume; diatomites. RESUMENPara este trabajo se ensayaron durante 2 años 54 PUZC, que contenían humo de sílice (SF) y diatomeas (D y N) (= puzolanas Z), mediante el método ASTM C 452-68, habiéndosele determinado a sus probetas su Vcl(=ΔL(%)/día). Los resultados obtenidos han confirmado que las reacciones puzolánicas de origen la SiO 2 r-de estas puzolanas Z, en un medio sulfático, han prevalecido más, con D y N, o menos, con SF, pronto, sobre la hidratación sulfática de sus PUZC, habiendo alcanzado su fin en los primeros 28 días. Luego, habiendo sido positivo el ensayo de Frattini, así como los ensayos normalizados equivalentes, el ensayo ASTM C 452-68 puede usarse también para diferenciar a 28 días, los PUZC preparados con puzolana Z o con cualquier otra puzolana natural o artificial, la cual podría o no, promover el desarrollo de baja, moderada o elevada RS. Únicamente, sería necesario establecer requerimientos y especificaciones químico-físicas apropiadas.

Sulfate Resistance in OPC and SRPC Containing Calcined Paper Sludge Waste: Ettringite or Thaumasite Formation

“…Where the SO 3 content is under 7.0%, they may be regarded as nonshrinkage cements, i.e., with a suitable amount of SO 3 < 7.0%, expansion in this new blended cement would be able to compensate for its hydraulic, thermal, or drying shrinkage. With a lower SO 3 content, the cement could be regarded simply as a blended cement (in keeping with the ΔL (%) versus time values found and quantified as per ASTM standard C452-68 (Talero 2011a(Talero , 2013 adapted by Talero (1986). Technologically speaking, the foregoing would be a beneficial consequence of ESE.…”

“…• In all certainty the approximately 33% metakaolin fraction would induce such stimulation Talero 1986Talero , 2011cTalero , 2012, • At the same time, the approximately 66% calcite filler fraction would very likely favor these pathways (Rahhal and Talero 2005;Talero 2013;Calleja and Aguanell 1980). Direct stimulation would be dually present: stimulating sulfate-mediated C 3 A hydration in the OPC when the surface of its particles were moistened by the mixing water and forming tri-, mono-, or hemi-carboaluminate hydrates, likewise sourced from the C 3 A in P1.…”

“…Indirect stimulation would also take place, albeit logically in the absence of pozzolanic activity, as logical, but in the presence of a low sulfate concentration (Rahhal et al 2012;Martín-Luengo 1997). Here the formation of calcium mono-carboaluminate hydrate would be favored over the formation of AFm whose SO 3 content would be transformed into ettringite (Rahhal et al 2012;Talero 2013). That would ultimately cause greater expansion and perhaps constitute a thaumasite precursor at more mature ages (Crammond 2003;Talero 1989).…”