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®-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.

O setor da construção tem se tornado um dos grandes motivos de preocupação ambiental, principalmente quando se trata da emissão de dióxido de carbono e geração de resíduos. Uma forma de mitigar tais impactos consiste na substituição de um sistema linear para um modelo de Economia Circular (EC). Nesse modelo, a reciclagem de Resíduos de Construção e Demolição (RCD) consiste em uma prática bastante estudada há mais de 20 anos, enquanto pesquisas sobre o reuso de elementos construtivos a partir da metodologia de projetar para desconstrução (DfD, Design for Deconstruction/Disassembly) tem ganhado destaque apenas nos últimos cinco anos. Dentre tais pesquisas, a avaliação da sustentabilidade por meio de indicadores ambientais é ainda mais escassa. Desta forma, o presente artigo faz uma revisão sistemática da literatura, reunindo trabalhos que apontam os principais avanços da prática DfD, com foco em estruturas de concreto armado sob a perspectiva da Avaliação do Ciclo de Vida (ACV). Com base nos artigos analisados, foi observado que, apesar da ausência de método unificado para quantificar seus benefícios, a prática de DfD se mostrou vantajosa para atenuar os impactos ambientais do setor da construção.

In the last several decades, the growth of Construction and Demolition Waste (CDW) production and the increased consumption of natural resources have led to promoting the use of secondary raw materials for a more sustainable construction. Specifically, the use of Recycled Concrete Aggregate (RCA), derived from waste concrete, for the production of Recycled Aggregate Concrete (RAC) has attracted a significant interest both in industry and in academia. However, the use of RAC in field applications still finds some barriers. In this context, the present study investigates experimentally the effects of freeze-thaw and wet-dry cycles on the stress transfer mechanisms of reinforced RAC elements through tension stiffening tests. First of all, the paper presents a detailed analysis of the degradation due to the aging process of RAC with RCAs obtained from different sources. Particularly, the results of tension stiffening tests are analyzed in terms of crack formation and propagation, matrix tensile strength contribution and steel-to-concrete bond. The results highlight that the pre-cracking elastic modulus, the first crack strength as well as the maximum concrete strength are strongly influenced by the presence of the Attached Mortar (AM) in RCA, as the former affects the concrete’s open porosity. Therefore, the amount of AM is identified as the key parameter for the evaluation of durability of reinforced RAC members: a degradation-law is also proposed which correlates the initial concrete open porosity with the damage observed in reinforced RAC elements.

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