12 GRC PRECAST ELEMENTS FOR EXTRA-LIGHT SELF-SUPPORTING FLOORS IN OFFICES AND RESIDENTIAL BUILDINGS

SUMMARY: Load-bearing floors for office and residential buildings are normally made of preca st concrete and have a self-weight of 2.50–3.50 kN/m², depending on the span and load. There is considerable interest in the building industry in the availability of very light floor components, in the order of 1.0 kN/m², to reduce the cost of structures, which are selfsupporting, have flat soffits, and minimum requirement for in-situ concrete and other works for finishing. This is particularly important for building in seismic areas, in the rehabilitation of old buildings, in high -rise buildings and with steel-frame structures. Optimal mix designs and manufacturing systems have been developed for industrial production of GRC floor slabs, and the criteria for the design of structural GRC floor elements have now been assessed through prototype tests at serviceability and ultimate limit states. Successful performances and results from a technical and economic point of view, related to the first industrial production and application for a new office building in Italy, are presented. The floor span is about 7.5 m with a live load of 3.5 kN/m 2 , and the soffit is required to be well finished and to hide the steel and concrete beams. Installation details of the GRC floor slabs with cast-in-situ beams of the same depth and with steel beams are also given. This type of GRC precast floor slab meets not only the structural and aesthetic requirements, but also provides fire protection to the steel structure.