Sulphur content of recycled aggregates applied in concrete production

Abstract

Abstract In this chapter, the influence of recycled aggregates (RAs) containing sulphur on recycled concrete (RC) is described. The RAs obtained by crushing clean concrete structures, concrete precast from unused components and clean civil engineering structures present amounts of sulphur and sulphates which are intentionally added to Portland cement, but that can adversely affect the RA and, consequently, the RA concrete. Detection methods are proposed to detect RAs containing excessive amounts of sulphates coming from the exposure of the original concrete structures to specific environments. Sources of sulphur is the RA coming from tested concrete specimens capped using pure sulphur or mortar of sulphur. The presence of sulphur in RAs can have adverse effects on the properties of fresh and hardened concrete. Losses of mechanical properties and durability are detected. The evaluation of the influence of sulphur on RC, according to its origin, and recommendations for their use are made.