Use of coarse recycled aggregates from precast concrete rejects: Mechanical and durability performance

• Aggregates recycled from precast concrete elements are well above average quality.
• Concrete made with them has very similar characteristics to conventional concrete.
• This is also true in terms of durability.
• Present limitations to the use of these recycled aggregates should be removed.

This paper presents the results of an experimental campaign developed with the aim of evaluating the effect of the incorporation in concrete of recycled aggregates from crushed elements produced by the precasting concrete industry. The specific purpose was to study the use of the coarse fraction of these aggregates. This was done by studying various replacement ratios of the coarse fraction of the aggregates. The possibility/need to correct the composition of concrete mixes with recycled aggregates was also investigated, by testing various contents of a superplasticizer, intending to replicate the characteristics of a reference concrete, i.e. a mix with an analogous composition but where all aggregates are natural. An extensive set of tests was performed to evaluate the mechanical and durability properties of all concrete mixes. The results prove that the concrete mixes with recycled aggregates have an equivalent performance to that of the reference concrete in most of the properties. In the others, where a performance loss was registered, that loss was lower than the one reported in the literature review performed. This was expected since the quality of the coarse aggregates recycled from precast elements is very good and totally fit for the production of new concrete, originating concrete compositions with good quality, namely in terms of hardened state properties. As expected the use of a superplasticizer is beneficial for concrete performance in all properties analysed.