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Hydration and strength development of calcite-rich wastepaper sludge ash

  • In paper recycling large amounts of waste sludge, containing organics as well as inorganic fillers of the recycled paper, are produced. A large fraction of these sludges is incinerated; the ashes generated in this process, often referred to as wastepaper sludge ash (WSA), have the potential to be used as binder material, either alone or as supplementary cementitious material. However, ashes from different paper mills differ in their Chemical and mineralogical composition, thus, the reaction products and the properties of the hardened binders may vary s i gn i fi cantley. In the present study, a calcite-rich WSA was analyzed for reaction products and strength development. The WSA contained, besides calcite, hydraulic phases such as tricalcium aluminate (C3A) and belite (C2S), lime as well as inert phases. When activated with water, the WSA yielded a compressive strength of up to 12.3 MPa and the major hydration product was monocarboaluminate (C4A CO2 IIH2O or C4ACH11). Activation withIn paper recycling large amounts of waste sludge, containing organics as well as inorganic fillers of the recycled paper, are produced. A large fraction of these sludges is incinerated; the ashes generated in this process, often referred to as wastepaper sludge ash (WSA), have the potential to be used as binder material, either alone or as supplementary cementitious material. However, ashes from different paper mills differ in their Chemical and mineralogical composition, thus, the reaction products and the properties of the hardened binders may vary s i gn i fi cantley. In the present study, a calcite-rich WSA was analyzed for reaction products and strength development. The WSA contained, besides calcite, hydraulic phases such as tricalcium aluminate (C3A) and belite (C2S), lime as well as inert phases. When activated with water, the WSA yielded a compressive strength of up to 12.3 MPa and the major hydration product was monocarboaluminate (C4A CO2 IIH2O or C4ACH11). Activation with 2M NaOH or 2M KOH solution caused a more rapid strength gain until one day of curing, but afterwards the strength development slowed down and the strength afiter 28 days was significantly lower than for the water-activated pastes. From TG analyses it is apparent that the higher strength of the alkaliactivated pastes after one day of curing was caused by a more rapid consumption of calcite and associated formation of C4ACH11. At later curing times the amount of calcite did not change substantially and consequently strength development almost ceased. The results demonstrate the complex influence of alkaline conditions on the hydration of WSA and show that the reaction products, which determine the durability properties of the hardened pastes (and materials made from it), of the calcite-rich WSA differ from the products of other WS As, as discussed in the article.zeige mehrzeige weniger

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Metadaten
Autor*innen:Gregor GluthORCiD, Christian Lehmann, Katrin RübnerORCiD, Hans-Carsten KühneORCiD
Dokumenttyp:Beitrag zu einem Tagungsband
Veröffentlichungsform:Graue Literatur
Sprache:Englisch
Titel des übergeordneten Werkes (Englisch):CIC 2014 - Concrete Innovation Conference 2014
Jahr der Erstveröffentlichung:2014
Erste Seite:1
Letzte Seite:8
Freie Schlagwörter:Alkali-activation; Strength; Tetracalcium monocarboaluminate; Wastepaper sludge ash (WSA)
Veranstaltung:CIC 2014 - Concrete Innovation Conference 2014
Veranstaltungsort:Oslo, Norway
Beginndatum der Veranstaltung:11.06.2014
Enddatum der Veranstaltung:13.06.2014
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:20.02.2016
Referierte Publikation:Nein
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