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New observations on the mechanism of lithium nitrate against alkali silica reaction (ASR) / X. Feng in Cement and concrete research, Vol. 40 N° 1 (Janvier 2010) 

Public ISBD [article]  in Cement and concrete research > Vol. 40 N° 1 (Janvier 2010) . - pp. 94-101 Titre : New observations on the mechanism of lithium nitrate against alkali silica reaction (ASR) Type de document : texte imprimé Auteurs : X. Feng, Auteur ; M.D.A. Thomas, Auteur ; T. W. Bremner, Auteur Article en page(s) : pp. 94-101 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Lithium  nitrate  Alkali  silica  reaction  (ASR)  Vycor  glass  Mechanism Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : In the current study, in order to elucidate the mechanisms for the favorable effects of lithium nitrate in controlling alkali silica reaction (ASR), vycor glass disk immersion specimens and glass disk–cement paste sandwich specimens were prepared and examined by XRD, SEM and Laser Ablation Induction Coupled Plasma Mass Spectrometry (LA-ICP-MS). Results showed that when glass disk was immersed in only NaOH solution, the glass was attacked by hydroxyl ions but no solid reaction product was found, thus the presence of calcium was essential for the formation of ASR gel. In the presence of lithium, the glass surface was covered by a thick layer of Li–Si crystal. With the addition of Ca(OH)2, the glass surface was completely covered by Li–Si crystal and a lithium-bearing low Ca–Na–(K)–Si gel. These two phases either form a dense matrix with Li–Si crystal serving as the framework, and the gel filling in the void space, or the Li–Si crystal serving as the foundation to completely cover the entire reactive SiO2 surface, and the gel sitting on top of these crystal particles. Hence, the suppressive effects of LiNO3 were attributed to the formation of a layer of Li–Si crystals intimately at the reactive SiO2 particle surface and the formation of Li-bearing low-Ca ASR gel products. The Li-bearing low-Ca ASR gels may have a dense and rigid structure, thus having low capacity to absorb moisture from the surrounding paste, and exhibiting a non-swelling property. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235562%23 [...] [article] New observations on the mechanism of lithium nitrate against alkali silica reaction (ASR) [texte imprimé] / X. Feng, Auteur ; M.D.A. Thomas, Auteur ; T. W. Bremner, Auteur . - pp. 94-101. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 40 N° 1 (Janvier 2010) . - pp. 94-101 Mots-clés : Lithium  nitrate  Alkali  silica  reaction  (ASR)  Vycor  glass  Mechanism Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : In the current study, in order to elucidate the mechanisms for the favorable effects of lithium nitrate in controlling alkali silica reaction (ASR), vycor glass disk immersion specimens and glass disk–cement paste sandwich specimens were prepared and examined by XRD, SEM and Laser Ablation Induction Coupled Plasma Mass Spectrometry (LA-ICP-MS). Results showed that when glass disk was immersed in only NaOH solution, the glass was attacked by hydroxyl ions but no solid reaction product was found, thus the presence of calcium was essential for the formation of ASR gel. In the presence of lithium, the glass surface was covered by a thick layer of Li–Si crystal. With the addition of Ca(OH)2, the glass surface was completely covered by Li–Si crystal and a lithium-bearing low Ca–Na–(K)–Si gel. These two phases either form a dense matrix with Li–Si crystal serving as the framework, and the gel filling in the void space, or the Li–Si crystal serving as the foundation to completely cover the entire reactive SiO2 surface, and the gel sitting on top of these crystal particles. Hence, the suppressive effects of LiNO3 were attributed to the formation of a layer of Li–Si crystals intimately at the reactive SiO2 particle surface and the formation of Li-bearing low-Ca ASR gel products. The Li-bearing low-Ca ASR gels may have a dense and rigid structure, thus having low capacity to absorb moisture from the surrounding paste, and exhibiting a non-swelling property. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235562%23 [...]

Summary of research on the effect of LiNO3 on alkali–silica reaction in new concrete / X. Feng in Cement and concrete research, Vol. 40 N° 4 (Avril 2010) 

Public ISBD [article]  in Cement and concrete research > Vol. 40 N° 4 (Avril 2010) . - pp. 636–642 Titre : Summary of research on the effect of LiNO3 on alkali–silica reaction in new concrete Type de document : texte imprimé Auteurs : X. Feng, Auteur Année de publication : 2012 Article en page(s) : pp. 636–642 Note générale : Bibliogr. Langues : Anglais (eng) Mots-clés : SEM;  EDX;  Alkali-aggregate  reaction;  Lithium  compounds Résumé : This paper summarizes findings from a research study conducted at the University of New Brunswick in collaboration with the University of Texas at Austin, and CANMET-MTL, on the effect of LiNO3 on ASR in new concrete. The studies included expansion testing, silica dissolution measurements and microstructural examinations of cement systems containing glass and two different reactive aggregates (NB and NS). Only a small proportion of the data are presented here for the purpose of highlighting the principal findings of this investigation. Based on these findings, it is proposed that the inhibiting effect of LiNO3 against ASR in new concrete is attributed to the formation of two reaction products in the presence of lithium, these being a crystalline lithium silicate compound (Li2SiO3) crystal and a Li-bearing, low Ca silica gel. These two phases could serve as a diffusion barrier and protective layer to prevent the reactive silica from further attack by alkalis. It was found that the reason the two reactive aggregates selected responded differently to LiNO3 was due to the difference in their textural features. The NB aggregate contained reactive volcanic glass particles, the surface of which was immediately and equally available to sodium, potassium and lithium, and thus a Li–Si barrier was able to form quickly. The reactive phase in the NS aggregate was microcrystalline and strained quartz, which was embedded in a dense matrix of a non-reactive predominantly alumino-silicate phase and was not easily accessible to lithium. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609002270 [article] Summary of research on the effect of LiNO3 on alkali–silica reaction in new concrete [texte imprimé] / X. Feng, Auteur . - 2012 . - pp. 636–642. Bibliogr. Langues : Anglais (eng) in Cement and concrete research > Vol. 40 N° 4 (Avril 2010) . - pp. 636–642 Mots-clés : SEM;  EDX;  Alkali-aggregate  reaction;  Lithium  compounds Résumé : This paper summarizes findings from a research study conducted at the University of New Brunswick in collaboration with the University of Texas at Austin, and CANMET-MTL, on the effect of LiNO3 on ASR in new concrete. The studies included expansion testing, silica dissolution measurements and microstructural examinations of cement systems containing glass and two different reactive aggregates (NB and NS). Only a small proportion of the data are presented here for the purpose of highlighting the principal findings of this investigation. Based on these findings, it is proposed that the inhibiting effect of LiNO3 against ASR in new concrete is attributed to the formation of two reaction products in the presence of lithium, these being a crystalline lithium silicate compound (Li2SiO3) crystal and a Li-bearing, low Ca silica gel. These two phases could serve as a diffusion barrier and protective layer to prevent the reactive silica from further attack by alkalis. It was found that the reason the two reactive aggregates selected responded differently to LiNO3 was due to the difference in their textural features. The NB aggregate contained reactive volcanic glass particles, the surface of which was immediately and equally available to sodium, potassium and lithium, and thus a Li–Si barrier was able to form quickly. The reactive phase in the NS aggregate was microcrystalline and strained quartz, which was embedded in a dense matrix of a non-reactive predominantly alumino-silicate phase and was not easily accessible to lithium. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609002270