Design of RAC structures - do conservative design approaches outweigh ecological benefits?

Shortage of natural resources and high CO₂ emissions require innovations in the construction industry. One simple yet promising approach is the use of Recycled Aggregate Concrete (RAC). In the past, several studies have been conducted focusing on the material properties of RAC, that on average are inferior compared to Natural Aggregate Concrete (NAC). Reaching the same compressive strength is usually accompanied by higher cement amounts which are unfavorable in terms of ecological aspects. Furthermore, design regulations such as in Second generation of Eurocode 2 (FprEC2) may require increased concrete volumes. Structural design aspects, however, are usually not included in the Life Cycle Assessment (LCA) of RAC when compared to NAC. Therefore, comparative case studies have been conducted at the Institute of Structural Concrete (IMB) of RWTH Aachen University, Germany, applying data of an existing LCA on structural members designed with RAC and NAC to show the impact of expanding the functional unit to the whole structural member, including effects resulting from design provision. The results show that small beneficial ecological effects of RAC may vanish if the dimensions of the structural member need to be enhanced. The need to include structural aspects in the evaluation of RAC on the basis of LCA is the main focus of this paper.

Subjects

application of Life Cycle Assessment data

case study

design of RC structures

Recycled aggregate concrete

resource-efficiency

DDC Class

620.11: Engineering Materials

600: Technology

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Design of RAC structures - do conservative design approaches outweigh ecological benefits?