Environmental Performance of Deconstructable Concrete Beams Made with Recycled Aggregates

The construction sector is one of the most energy-intensive and raw-material-demanding human activities and, hence, contributes a significant share of greenhouse gas emissions. As a matter of principle, making the construction sector "greener" is one of the main challenges for policy makers, private companies and the scientific community. For this reason, one of the most promising actions is based on recycling Construction and Demolition Waste (CDW) and converting them into secondary raw materials for the construction sector itself. Moreover, the reduction of the environmental impact can be further amplified through the optimization of the production, assembly and deconstruction/reuse procedures and through the maximization of the service life. In this aim, the present work aims at analyzing the environmental performance of duly sized and designed prefabricated Decontructable and Reusable Beam (DRB) incorporating with Recycled Concrete Aggregates (RCA) assembled by means of an innovative system based on a memory (R)-steel prestressing technique. The environmental performance is evaluated through Life Cycle Assessment with a cradle-to-gate approach: the analysis of 16 midpoint impact categories was conducted using the methodology proposed by EN15804. In this context, three allocation scenarios for avoided impacts due to reuse (100-0, 50:50 and 0-100) were considered, and a sensitivity analysis was performed. It was verified that due to the higher amount of post-tensioning required for the innovative shape memory alloy steel bars, the DRBs present inferior environmental performance than the Ordinary Beams (ORB). However, when analyzing the reuse scenarios, it was observed that the DRB could have considerably lower impacts, depending on the type of allocation procedure adopted in LCA modeling. This study brings as the main contribution an evaluation and some design guidelines for the development of circular concrete structures based on the principles of Design for Deconstruction (DfD) and the prefabricated process.