Assessment of AAR and Sulfate Attack on Wadi Gravel Concrete after 4 Years in Service

Abstract

Wadi gravel is a local aggregate in Qatar that could contribute to enhanced sustainability by replacing expensive imported gabbro. The material needs to be processed before use to reduce sulfate content to acceptable levels. The paper presents the performance assessment of three full-scale buildings, variously made with 50% and 100% Wadi gravel and conventional gabbro concretes. Site monitoring up to four years in service demonstrated the strength development with age and resistance to the aggressive exposure conditions in Qatar. The Wadi gravel concrete exhibited at least similar performance to the gabbro concrete, and excellent durability as defined in national construction specifications. The paper provides initial long-term assessment and builds on previous publications by the authors, for initial assessment of Wadi gravel concrete. In an earlier investigation by the authors, a difference was observed between the concrete prism expansion test results of RILEM AAR-4.1 and BS 812-123. Wadi gravel was classified as potentially reactive in the more accelerated RILEM AAR-4.1 and of low reactivity in the more realistic exposure BS 812-123. Petrographic examination of the hardened concrete after four years in service has shown no evidence of cracking or signs of distress or deterioration and confirmed the BS 812-123 interpretation of alkali-silica reactivity of Wadi gravel concrete. The results obtained in this investigation provide more confidence for the wider and efficient use of Wadi gravel in structural concrete.