The potential for direct reuse of precast concrete slabs in buildings with “wet” joints

Today, many buildings are built with precast concrete slabs each year, and as per tradition, these slabs are joined by pouring in-situ mortar in the joints between the slab elements. This is typically done to ensure the structural performance when the entire level of a building needs to perform as one rigid body. However, the consequence of the mortar-joints is that future dismantling is difficult as it requires extensive and costly use of diamond saws. Therefore, disassembly and direct reuse of concrete slab elements are rarely seen. Instead, the concrete is often crushed and used for, e.g., road filling. The global focus on reducing carbon dioxide from cement production and challenges with limited natural resources means that the production of new concrete must be reduced in the future. Direct reuse of concrete elements is essential to this transformation. More recently, methods have been employed to apply “dry” mechanical joints (e.g., steel brackets) specifically to enable a simpler disassembling process after end lifetime of buildings. Several challenges exist for the dry connections, such as more complex elements, labour-demanding assembly, higher cost, and problems with local damages, fire protection and robustness in service. Despite the trend in development and research activities in dry connection joints, the opportunity of modifying the simple, traditional “wet” mortar joints to create Design for Disassembly (DfD) has only been superficially investigated. The article unfolds the potential of a new type of wet concrete joints with a review of the challenges and limitations. The proposed solution to achieve DfD for wet connections is to reduce the mortar strength and stiffness and disassemble by pulling with a crane.