The paper presents a detailed experimental investigation on the behaviour of demountable shear connections within a composite floor system which has been developed within the LWT-FLOOR project at the Faculty of Civil Engineering in Zagreb. One of the project's focuses is to address key sustainability and usability challenges in the construction industry, particularly related to the life cycle of structural elements. This study examines the mechanical behaviour of demountable bolted shear connection in an innovative composite system comprising of cold-formed steel (CFS) girders and concrete slab. Two distinct configurations of CFS-concrete composite specimens were investigated: the BB series, which consists of back-to-back CFS profiles, and the BCWB series, which incorporates additional corrugated web between the C profiles. A comprehensive set of 18 push-out tests was conducted to evaluate the key performance indicators of the shear connections, including failure modes, shear resistance, ductility, and initial stiffness. The obtained results provide valuable insights into the structural behaviour of demountable shear connections, revealing their complex behaviour which is affected by the interaction of several failure modes. Furthermore, an additional corrugated web in the BCWB series significantly improves resistance but has only a small influence on the overall ductility and initial stiffness when compared to the CFS girder without the corrugated web. This research highlights the potential of demountable shear connections as a sustainable and reusable alternative in composite floor systems, offering benefits in terms of structural efficiency, ease of assembly and disassembly, and is in line with required circular economy principles in construction.