Reactivity of reclaimed concrete aggregate produced from concrete affected by alkali–silica reaction / Medhat H. Shehata in Cement and concrete research, Vol. 40 N° 4 (Avril 2010)  

Public ISBD [article]  inCement and concrete research > Vol. 40 N° 4 (Avril 2010) . - pp. 575–582 Titre : Reactivity of reclaimed concrete aggregate produced from concrete affected by alkali–silica reaction Type de document : texte imprimé Auteurs : Medhat H. Shehata, Auteur Année de publication : 2012 Article en page(s) : pp. 575–582 Note générale : Bibliogr. Langues : Anglais (eng) Mots-clés : Alkali–Aggregate Reaction  Reclaimed concrete aggregate  Fly Ash  Lithium Compound SEM Résumé : This paper presents results from a research program that focused on studying the reactivity of reclaimed concrete aggregate (RCA) produced from concrete affected by alkali–silica reaction (ASR). The results showed that RCA produced from ASR-affected concrete causes significant expansion when used in new concrete. The expansion was similar to that produced in concrete containing the reactive aggregate used originally in the old concrete. It is believed that crushing the old concrete exposed fresh faces of the reactive aggregate which causes renewed reaction and expansion in the new concrete. The alkalis contributed from the RCA are also believed to contribute to the expansion. The amount of supplementary cementing materials required to mitigate the expansion in new concrete containing ASR-affected RCA was higher than those normally needed in concrete containing the virgin reactive aggregate. The results showed a good agreement between the 14-day expansion of accelerated mortar bars and the expansion of concrete prisms. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609002087 [article] Reactivity of reclaimed concrete aggregate produced from concrete affected by alkali–silica reaction [texte imprimé] / Medhat H. Shehata, Auteur . - 2012 . - pp. 575–582. Bibliogr. Langues : Anglais (eng) in Cement and concrete research > Vol. 40 N° 4 (Avril 2010) . - pp. 575–582 Mots-clés : Alkali–Aggregate Reaction  Reclaimed concrete aggregate  Fly Ash  Lithium Compound SEM Résumé : This paper presents results from a research program that focused on studying the reactivity of reclaimed concrete aggregate (RCA) produced from concrete affected by alkali–silica reaction (ASR). The results showed that RCA produced from ASR-affected concrete causes significant expansion when used in new concrete. The expansion was similar to that produced in concrete containing the reactive aggregate used originally in the old concrete. It is believed that crushing the old concrete exposed fresh faces of the reactive aggregate which causes renewed reaction and expansion in the new concrete. The alkalis contributed from the RCA are also believed to contribute to the expansion. The amount of supplementary cementing materials required to mitigate the expansion in new concrete containing ASR-affected RCA was higher than those normally needed in concrete containing the virgin reactive aggregate. The results showed a good agreement between the 14-day expansion of accelerated mortar bars and the expansion of concrete prisms. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609002087

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The role of alkali content of Portland cement on the expansion of concrete prisms containing reactive aggregates and supplementary cementing materials / Medhat H. Shehata in Cement and concrete research, Vol. 40 N° 4 (Avril 2010)  

Public ISBD [article]  inCement and concrete research > Vol. 40 N° 4 (Avril 2010) . - pp. 569–574 Titre : The role of alkali content of Portland cement on the expansion of concrete prisms containing reactive aggregates and supplementary cementing materials Type de document : texte imprimé Auteurs : Medhat H. Shehata, Auteur ; Michael D.A. Thomas, Auteur Année de publication : 2012 Article en page(s) : pp. 569–574 Note générale : Bibliogr. Langues : Anglais (eng) Mots-clés : Alkali–aggregate reaction  Alkalis Fly ash Pore solution Modified accelerated mortar bar test Résumé : This paper presents results covering the effects of alkali content of Portland cement (PC) on expansion of concrete containing reactive aggregates and supplementary cementing materials (SCM). The results showed that the alkali content of PC has a significant effect on expansion of concrete prisms with no SCM. When SCM is used, the expansion was found to be related to both the chemical composition of the SCM and, to a lesser extent, the alkali content of the PC. The concrete expansions were explained, at least partly, on the basis of the alkalinity of a pore solution extracted from hardened cement paste samples containing the same cementing blends. An empirical relation was developed correlating the chemical composition (Ca, Si and total Na2Oe) of the cementing blend (PC + SCM) and the alkalinity of the pore solution. Results from accelerated mortar bar test (ASTM C 1260) and a modified version thereof are also presented. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609002075 [article] The role of alkali content of Portland cement on the expansion of concrete prisms containing reactive aggregates and supplementary cementing materials [texte imprimé] / Medhat H. Shehata, Auteur ; Michael D.A. Thomas, Auteur . - 2012 . - pp. 569–574. Bibliogr. Langues : Anglais (eng) in Cement and concrete research > Vol. 40 N° 4 (Avril 2010) . - pp. 569–574 Mots-clés : Alkali–aggregate reaction  Alkalis Fly ash Pore solution Modified accelerated mortar bar test Résumé : This paper presents results covering the effects of alkali content of Portland cement (PC) on expansion of concrete containing reactive aggregates and supplementary cementing materials (SCM). The results showed that the alkali content of PC has a significant effect on expansion of concrete prisms with no SCM. When SCM is used, the expansion was found to be related to both the chemical composition of the SCM and, to a lesser extent, the alkali content of the PC. The concrete expansions were explained, at least partly, on the basis of the alkalinity of a pore solution extracted from hardened cement paste samples containing the same cementing blends. An empirical relation was developed correlating the chemical composition (Ca, Si and total Na2Oe) of the cementing blend (PC + SCM) and the alkalinity of the pore solution. Results from accelerated mortar bar test (ASTM C 1260) and a modified version thereof are also presented. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609002075

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