The aim of this project is to advance towards net-zero concrete production by exploring the potential of recycled aggregates derived from lightweight concretes, with a focus on accelerated carbonation strategies. The project addresses the significant challenge of limited recycling options for lightweight concretes, which are currently excluded from standard recycling practices.

The primary objective is to develop methods to recyce and reuse lightweight concrete elements at the end of their life cycle, converting them into Recycled Lightweight Concrete Aggregates (RLCA). These RLCA will be used to produce new concretes, with the goal of replicating the properties of the original concretes.

This study will investigate key aspects of lightweight concrete recycling, including crushing, processing, and screening techniques to produce RLCA. Physical and CO2 absorption properties of RLCA will be evaluated to assess their suitability for incorporation into new concrete mix design, and to establish a basis for quantifying their CO2 reabsorption potential for consideration in life cycle assessments.

In the next phase, recycled lightweight concretes made from RLCA will be tested to verify their design and performance characteristics. Three categories of lightweight concrete will be considered: structural lightweight concrete (LC), lightweight aggregate concrete (LAC), and infra-lightweight concrete (ILC). Structural properties such as compressive strength, modulus of elasticity, and thermal conductivity will be evaluated to ensure that these recycled concretes meet the requirements for structural applications.

The research aims to reduce the environmental impact by improving material circularity, reducing CO2 emissions, and validating the structural performance of recycled lightweight concrete. By focusing on the CO2-sequestration potential of recycled materials and establishing recycling loops, the project promotes a closed-loop sustainability model for lightweight concrete. This work addresses the urgent need for more sustainable construction practices and provides innovative pathways to a greener future.

Applicants: Karl-Christian Thienel, Univ.-Prof. Dr.-Ing.