ASR performance of concrete at external alkali supply – effects of aggregate mixtures and blended cement

Abstract

ABSTRACT The long-term durability of concrete pavements in wet-freeze climate is influenced by deicing salts used for winter maintenance of roads. Alkaline deicers could also be an external source of alkalis, therefore, their role in respect to the development of deleterious alkali-silica reaction (ASR) should be considered. The performance of mineral aggregate mixtures in concrete was studied using RILEM test procedure ‘60°C concrete test with external alkali supply’. Air-entrained concrete specimens were exposed to cyclic temperature changes, wetting-drying and NaCl solution immersion. Tests revealed the development of concrete expansion in time and associated changes of its elastic modulus for 31 mixtures of fine and coarse aggregate and Portland and fly ash or slag blended cements. The expansive behaviour of air-entrained concrete was strongly influenced by the presence of micro- and cryptocrystalline silica in aggregates. A replacement of nonreactive limestone sand by moderately reactive quartz sand resulted in a substantial enhancement of concrete expansion by a factor of three. The observed reduction of elastic modulus was correlated with more abundant presence of alkali-silica reaction products in concrete. Effects of cement type (CEM I, CEM II/A-V, CEM II/B-S) on the ASR performance of concrete with crushed coarse aggregate and quartz sand are discussed.