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Internal sulfate resistance of concrete

  • If the amount of sulfate within the mix design for concrete is not balanced, ettringite formation which first controls solidification continues while the concrete is hardening. Ettringite forms by reaction of sulfate contained in the cement or in some admixture with calcium aluminate (C3A) as cement component. The “late primary ettringite formation” promotes an increase in volume within the hardened concrete leading to cracks. To analyze the effect of substituting part of ordinary Portland cement (OPC) by a treated brown coal fly ash mortar bars were tested according to ASTM C452. This test method was originally developed to extrapolate from the internal to external sulfate attack and is based on the idea that by testing a concrete mixture containing sulfate the process of deterioration is accelerated because it does not have to diffuse into the concrete before reaction first. In addition to the samples prescribed in ASTM C452 further samples in the size of the German SVA procedureIf the amount of sulfate within the mix design for concrete is not balanced, ettringite formation which first controls solidification continues while the concrete is hardening. Ettringite forms by reaction of sulfate contained in the cement or in some admixture with calcium aluminate (C3A) as cement component. The “late primary ettringite formation” promotes an increase in volume within the hardened concrete leading to cracks. To analyze the effect of substituting part of ordinary Portland cement (OPC) by a treated brown coal fly ash mortar bars were tested according to ASTM C452. This test method was originally developed to extrapolate from the internal to external sulfate attack and is based on the idea that by testing a concrete mixture containing sulfate the process of deterioration is accelerated because it does not have to diffuse into the concrete before reaction first. In addition to the samples prescribed in ASTM C452 further samples in the size of the German SVA procedure were tested also designed for accessing the external sulfate resistance. The results show that while the replacement of 25 % of cement by brown coal fly ash leads to length changes around the limit defined by ASTM, the substitution of 50 % cement exceeded the limit by a multiple. The progress of expansion is the very similar for the two geometries tested. In-situ XRD measurements confirmed that while for pastes made of OPC the formation of ettringite is completed after 20 hours, this is not true for the mixtures containing the brown coal fly ash. In a different study the effect of hydrothermal treatment on the phase composition of ultra-high-performance concrete was analyzed. The results show that the sulfate and aluminate resulting from the decomposition of ettringite are bound into new phases. If this binding is permanent this might allow the larger use of sulfate bearing raw materials.zeige mehrzeige weniger

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  • 2021_v. Werder et al._Internal sulfate resistance.pdf
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Metadaten
Autor*innen:Julia von WerderORCiD, Sebastian SimonORCiD, Birgit MengORCiD
Dokumenttyp:Beitrag zu einem Tagungsband
Veröffentlichungsform:Graue Literatur
Sprache:Englisch
Titel des übergeordneten Werkes (Englisch):EuroCoalAsh 2021 Conference “International Conference for Promoting the Use of Coal Combustion Products (CCPs) in Construction”
Jahr der Erstveröffentlichung:2021
Organisationseinheit der BAM:7 Bauwerkssicherheit
7 Bauwerkssicherheit / 7.1 Baustoffe
7 Bauwerkssicherheit / 7.4 Baustofftechnologie
Herausgeber (Institution):Aristotle University Research Dissemination Centre (KEDEA)
Verlagsort:Thessaloniki
Erste Seite:131
Letzte Seite:137
DDC-Klassifikation:Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurwissenschaften und zugeordnete Tätigkeiten
Freie Schlagwörter:Brown coal fly ash; Ettringite; Hydrothermal treatment; In-situ XRD; Internal sulfate resistance; Test methods
Themenfelder/Aktivitätsfelder der BAM:Material
Material / Degradation von Werkstoffen
Veranstaltung:EuroCoalAsh 2021 Conference
Veranstaltungsort:Online meeting
Beginndatum der Veranstaltung:02.11.2021
Enddatum der Veranstaltung:04.11.2021
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:22.12.2021
Referierte Publikation:Nein
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