Characterisation of recycled concrete aggregates from construction and demolition wastes

Abstract

Construction and demolition waste form a significant problem in terms of environmental pollution and material depletion. Concrete, as part of construction and demolition waste, is already responsible for 9% of the total anthropogenic carbon dioxide emissions. Consequently, it is important to alleviate the environmental stress of concrete by replacing virgin aggregates and cement by recycled aggregates and liberated cement. This study determines how the properties of recycled aggregates and virgin (new) aggregates compare for using recycled aggregates in a new concrete mixture.
Recycled aggregate properties are examined by performing a variety of experiments, namely
water absorption and specific gravity, Los Angeles abrasion, flakiness and shape index and
compressive strength. Each experiment describes a different characteristic of the aggregates
creating a clear picture of their properties. The properties of virgin aggregates have been
obtained from literature.
In addition, a milling method has been examined as a possible new step in the recycling chain
for liberating cement paste from the fine recycled aggregates.
Water absorption and interfacial transition zone formed problems for the recycled aggregates,
but they show excellent properties in terms of compressive strength, resistance to abrasion,
grain interlocking and shape characteristics.
While very different from each other, recycled aggregates show very good properties when
compared to virgin aggregates giving them potential to be used in new concrete mixtures.