Use of γ-Al2O3 to prevent alkali-silica reaction by altering solid and aqueous compositions of hydrated cement paste

• Published in: Cement and concrete research Vol. 124; p. 105817
• Main Authors: Zhou, Jin, Zheng, Keren, Liu, Zanqun, Chen, Lou, Lippiatt, Nicholas
• Format: Journal Article
• Language: English
• Published: Elmsford Elsevier Ltd 01.10.2019; Elsevier BV
• Subjects: Accelerated tests; Alkali-silica reaction; Alkali-silica reactions; Aluminum oxide; Aqueous Al species; Cement; Cement paste; Chemical precipitation; Hydrates; Mortars (material); Phase assemblage; Pore solution; Portland cements; Silicon dioxide; Transitional aluminas; Phase assemblage; Pore solution; Alkali-silica reaction; Aqueous Al species
• ISSN: 0008-8846; 1873-3948
• DOI: 10.1016/j.cemconres.2019.105817

This study aims to explore the feasibility of preventing alkali-silica reaction (ASR) in concrete by adding γ-Al2O3. A binder composed of 90% Portland cement and 10% γ-Al2O3 was studied, where γ-Al2O3 was incorporated as a solid aluminum source to produce Al-bearing hydrates of high solubility, thus increasing aqueous Al concentration. The precipitation of katoite was predicted through thermodynamic simulation and confirmed experimentally by means of XRD and TGA in the hydrating binder. As a result, Al concentration in pore solution increased up to nearly 0.8 mM at 90 days. At such high concentration, the efficiency of aqueous Al in controlling alkali-silica reaction was confirmed by accelerated mortar bars tests. Clear surfaces of aggregates in mortar accelerated for 400 days (ASTM C227 conditions) were observed through SEM examination, which demonstrates the resistance of aqueous Al on the dissolution of reactive silica.