Preliminary study on the fresh and mechanical properties of UHPC made with recycled UHPC aggregates

The recycling of construction and demolition waste material reduces disposal of material and also the consumption of resources, therefore promoting sustainability in construction. Ultra-high performance concrete (UHPC) is a relatively new material and its feasibility to be recycled needs to be verified. This work investigates the recyclability of UHPC disposed elements, including the production of recycled aggregates and fibres from UHPC. The feasibility of recycled aggregates and fibres at different replacement rates was evaluated through the assessment of rheological and mechanical properties of the newly produced UHPC elements. Concrete mixes with replacement of aggregates at 50% and 100%, displayed compression strength comparable to original UHPC, maintaining the original deflection-hardening response. However, their workability was slightly reduced when increasing the content of the recycled material. Mixes with recycled fibres experienced residual strength losses and behaved as deflection-softening materials in the case of complete replacement.