Valorization of Masonry CDW as Recycled Aggregate in Lightweight Structural Concrete

Lightweight structural concrete offers an opportunity to decrease the dead load which is of great importance for improving both resource efficiency and earthquake behaviour of reinforced concrete and combined structures. Manufactured lightweight aggregate however are characterised by high embodied energy which reduces the environmental benefits of lightweight concrete. The aim of the current study was to evaluate the possibility for up-cycling of clay bricks construction and demolition waste (CDW) as aggregate in structural concrete. Three concrete compositions having different content of recycled bricks aggregate (RBA) were designed. The main characteristics of that concrete, required for the design of reinforced concrete structures, were determined. The bonding between RBA concrete and steel reinforcement bars was studied. Some durability (drying shrinkage and carbonation) were also investigated. It was concluded, that the valorization of masonry CDW as aggregate for concrete is possible and, depending on the RBA content, concrete for various purposes might be produced – an ordinary structural concrete when RBA share is of order of 20% of the total coarse aggregate and a lightweight concrete, having reduced dead load and satisfactory compressive strength and bonding with rebars when the replacement rate varies from 60% to 100%. Other aspects of the RBA lightweight concrete such as modulus of elasticity, shrinkage and carbonation depth showed lower performances. Therefore, RBA containing concrete requires adjustments in the mix design and in the behaviour prediction models, as well as measures to ensure the durability, similar to those for concrete with other type of lightweight aggregate.