Modern construction faces the dual pressures of environmental responsibility and technological advancement. This research focuses on lightweight concretes designed for monolithic exterior walls that inherently meet thermal requirements without additional insulation. These concretes are well positioned to address the present challenges by offering a unique combination of low density, thermal efficiency, and potential for material circularity. The experimental findings are based on three fundamental case studies, each exploring different strategies for optimizing lightweight concrete technologies under real-world conditions and providing empirically based solutions for their integration into modern construction practices. While pumping is well established for normal concrete, the porous, lightweight aggregates of lightweight concrete present unique challenges. For the first time, it has been demonstrated that infra-lightweight concrete can be successfully pumped using piston, eccentric screw, and rotor pump, provided that the mix design is optimized and handling is carefully managed. The rotor pump proved most efficient, minimizing mechanical abrasion and preserving workability. Key properties, including compressive strength, flexural strength, and modulus of elasticity, remained consistent, confirming that pumping does not ompromise material integrity. The combination of lightweight concrete with an open structure and steel frameworks presents an innovative solution for prefabricated wall elements that meet modern energy requirements. The concrete mix is optimized for maximum density reduction to achieve low thermal conductivity, while providing sufficient lateral support for the slender steel structure, which is susceptible to buckling. Key concrete performance parameters such as strength, modulus of elasticity, shrinkage, creep, and sustained loading behavior aligned with normative guidelines. Mechanical tests demonstrated that the composite elements achieved three times the load capacity of standalone steel sections. The study also confirmed the scalability of this design from laboratory testing to factory production. Recycling of infra-lightweight concrete addresses existing limitations in recycling standards and presents viable pathways for sustainable construction. The recycled products have been evaluated for their suitability in new concrete formulations and their potential to sequester CO 2. The mix design of the recycled concrete uses 100 % recycled material as the aggregate source and was optimized to replicate the properties of the original concrete, achieving the same strength class while maintaining the lowest possible density and thermal conductivity. Test results showed mechanical properties and thermal conductivity comparable to the original concrete. Accelerated carbonation tests on recycled material revealed significant CO 2 absorption, capturing up to 30 % of the original emissions and achieving a 50 % reabsorption rate relative to cement emissions. The multi-generational reuse of materials through recycling and recarbonation highlights the circular potential of lightweight concretes. Integrating the recarbonation potential into life cycle assessments presents a viable approach toward net-zero concrete production, while reducing resource consumption and construction waste. Future work is needed to refine material classification and standardization to facilitate wider adoption of these innovative lightweight concretes. Aligning material properties with existing standards and developing tailored guidelines for pumping, composite systems, and recycling practices will be critical. This will positively impact regulatory acceptance, industrial scalability, and the long-term promotion of circular design practices.      «

Modern construction faces the dual pressures of environmental responsibility and technological advancement. This research focuses on lightweight concretes designed for monolithic exterior walls that inherently meet thermal requirements without additional insulation. These concretes are well positioned to address the present challenges by offering a unique combination of low density, thermal efficiency, and potential for material circularity. The experimental findings are based on three fundamen...     »