The construction sector plays a significant role in the economy, raw material extraction, and waste generation. In the conventional linear economy model, extracting raw materials for construction and disposal of construction and demolition waste undermine sustainable development. Concrete is a predominant construction material made of graded aggregates (i.e. sands and gravel, accounting for 60-80% of the concrete volume), water, and cement. Recycling the demolition construction waste by crushing it into aggregate effectively mitigates the problems of waste generation and raw resource depletion. In the past, recycled aggregate (RA) is mainly used in non-structural construction such as pavement and backfill, due to its lower quality than the natural aggregate. Currently, the EN 206 and its revised national annexes allow the limited percentages of the coarse aggregate in concrete to be substituted by RA, e.g. at most 0-50% depending on the exposure classes and national limitations. Further, reduction factors for mechanical properties of recycled aggregate concrete (RAC) have been introduced into the new second generation of Eurocode 2 (FprEN 1992-1-1: 2023), enabling the application of RAC in concrete structures. However, to date, no application rules for RAC have been incorporated into the standards for steel–concrete composite structures.
Aiming to promote more applications of RA, the RECOMPOSE project is exploring the possibility of using higher percentages of RA in steel-concrete composite floor systems upon satisfactory structural safety. The research focuses on the shear resistance of headed stud connectors embedded in RAC slabs governing the structural performance and integrity of the composite floor systems. In addition, whether applying the reduced RAC properties recommended by the upcoming Eurocode 2 into the resistance model of headed stud shear connections in second generation of Eurocode 4 (FprEN 1994-1-1) leads to a safe design is questionable. Accordingly, the RECOMPOSE project is working to answer this question by performing reliability analyses.
The host professor of the RECOMPOSE project served as the convenor of project team CEN/TC250/SC4.T6 within the EU-Mandate M515 which is responsible for developing the second generation of Eurocode 4. He guides the project with standardization-related expertise and engages the project with standardization processes. The standardization-oriented strategy facilitates the dissemination and exploitation of the project outputs and maximizes their impacts. It will trigger the research for the development of Eurocode 4 considering RAC for composite floor systems, which will have a huge impact making possible a large-scale application of RAC in buildings in the future.
