Award of Excellence: Special Projects Category
Seismic Retrofitting of Floors with Low Thickness UHPFRCC Micro-Concrete
Submitted by Tecnochem Italiana S.p.A.
IRCCS Istituto Tumori Giovanni Paolo II
SGM Ingegneria SRL
Salvatore Matarrese S.p.A.
Tecnochem Italiana S.p.A.
The Domenico Cotugno Hospital, constructed in 1930 in Bari, Italy, and located in Seismic Area Class 3, was recently renovated to be the new headquarters of the IRCCS Istituto Tumori Giovanni Paolo II. As a part of the analysis for design of the project, it was determined that the existing structure required seismic strengthening to bring the building into compliance with current codes.
One of the key elements of the seismic strengthening plan was membranic reinforcement of the floors using fiber-reinforced micro-concrete that was bonded to the existing concrete floors. This bond was needed to ensure that horizontal forces from an earthquake are transferred to the new partitions and existing walls.
The membranic reinforcement of the floors was achieved by using specially formulated ultra-high-performance fiber-reinforced cementitious composite (UHPFRCC) micro-concrete. The UHPFRCC material was formulated to be applied in a layer on reinforced floors.
UHPFRCC micro-concrete is a fiber-reinforced, self-consolidating mixture with very high mechanical strength and fracture energy. The three component product consists of a powder component, a liquid additive, and steel and polymer microfibers (0.6 in. [15 mm] long). The product sets in about 1 hour and develops high strength in the early stages so it can be opened to foot traffic after about 14 hours.
The main advantages of this system are minimal application thickness (0.6 to 0.8 in. [15 to 20 mm]), resulting in minimal increased load; adhesion to the substrate without necessity of connectors or resins; no reinforcement mesh required; very high ductility and resistance to cyclic load; increased bearing capacity in terms of bending moment and stiffness with reduced floor deflection; speed of application because of self-leveling material properties; and no construction or contractive joints.