Analysis of the efficiency of semi-precast lightweight composite floor slab installation technology

The article is devoted to the analysis of the BubbleDeck technology as an innovative solution for lightweight floor slabs in the construction of multi-story frame buildings, as well as the justification of its applicability in comparison with the monolithic Cobiax system. The use of void-formers allows reducing the dead weight of slabs by 20–40% and cutting concrete consumption by up to 40% without compromising load-bearing capacity. However, the economic feasibility of a particular system is determined not only by structural parameters but also by the presence of specialized precast concrete plants in the construction region. The European experience in the application of lightweight floor slabs is examined, specifically the Cobiax company as a leader in the monolithic segment, and the Danish company BubbleDeck as the pioneer in offering precast-monolithic bidirectional slabs with integrated void-formers. The structural features of the BubbleDeck system are analyzed. The slab has a two-layer structure consisting of a 60 mm precast bottom layer with factory-installed spherical void-formers and a monolithic top layer made of high-strength lightweight concrete (LC40). The system is designed for spans of 7.2–8.4 m, with slab thicknesses ranging from 230 to 600 mm. As a representative of the monolithic segment, the Cobiax system with ellipsoid inserts for spans of 6.0–8.4 m is considered. Differences between the systems in terms of formwork, reinforcement, and labor intensity of installation are analyzed. The factory readiness of BubbleDeck slabs eliminates the need for solid plywood formwork – linear supports are sufficient. Factory-controlled reinforcement and ball spacing minimize the risk of void-former buoyancy during concreting, which remains a relevant problem for monolithic options. The bottom surface of the slab turns out to be smooth, requiring no plastering. The installation of a single panel with an area of up to 20–30 m² is faster than the assembly and disassembly of formwork for monolithic options, allowing for a construction pace of one floor per week. At the same time, high factory readiness generates new costs associated with the transportation of large-sized elements, rigging, crane lifting, and precise positioning of panels at the site. The transport component per 1 m² increases in proportion to the distance, and at a distance of over 150 km, it becomes comparable to the savings achieved on formwork operations.