New observations on the mechanism of lithium nitrate against alkali silica reaction (ASR)

• Published in: Cement and concrete research 2010-01, Vol.40 (1), p.94-101
• Main Authors: Feng, X., Thomas, M.D.A., Bremner, T.W., Folliard, K.J., Fournier, B.
• Format: Article
• Language: English
• Subjects: ABLATION; ALKALI METAL COMPOUNDS; ALKALI METALS; Alkali silica reaction (ASR); ALKALINE EARTH METAL COMPOUNDS; Applied sciences; BUILDING MATERIALS; Buildings. Public works; CALCIUM COMPOUNDS; CALCIUM HYDROXIDES; CEMENTS; CHALCOGENIDES; COHERENT SCATTERING; COLLOIDS; Corrosion; CRYSTALS; DEFORMATION; DIFFRACTION; DISPERSIONS; Durability. Pathology. Repairing. Maintenance; ELECTRON MICROSCOPY; ELEMENTS; Exact sciences and technology; GELS; GLASS; HYDROGEN COMPOUNDS; HYDROXIDES; ICP MASS SPECTROSCOPY; LITHIUM; LITHIUM COMPOUNDS; Lithium nitrate; LITHIUM NITRATES; MASS SPECTROSCOPY; MATERIALS; MATERIALS SCIENCE; Mechanism; METALS; MICROSCOPY; MINERALS; NITRATES; NITROGEN COMPOUNDS; OXIDE MINERALS; OXIDES; OXYGEN COMPOUNDS; SCANNING ELECTRON MICROSCOPY; SCATTERING; SILICA; SILICON COMPOUNDS; SILICON OXIDES; SODIUM COMPOUNDS; SODIUM HYDROXIDES; SPECTROSCOPY; SWELLING; VOIDS; VYCOR; Vycor glass; X-RAY DIFFRACTION
• ISSN: 0008-8846; 1873-3948
• DOI: 10.1016/j.cemconres.2009.07.017

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 SiO 2 surface, and the gel sitting on top of these crystal particles. Hence, the suppressive effects of LiNO 3 were attributed to the formation of a layer of Li–Si crystals intimately at the reactive SiO 2 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.