Strengthening Two-Way Reinforced Concrete Floor Slabs Using Polypropylene Fiber Reinforcement

Two methods for strengthening two-way reinforced concrete floor slabs subjected to out-of-plane bending loads are compared through experiments on seven test specimens and subsequent analyses. The seven test specimens were two unstrengthened regular reinforced concrete slabs (control), two slabs strengthened using glass-fiber-reinforced polymer (GFRP) sheets, and three slabs strengthened with an innovative method of applying a layer of fiber-reinforced cement (FRC) in varying thicknesses to the tension face of the slab. All specimens were $1.5\mathrm{m}\times 1.5\mathrm{m}$ ($5\mathrm{ft}\times 5\mathrm{ft}$) and were designed to resist bending in both directions. The advantages and disadvantages of the two strengthening methods are discussed in terms of structural considerations, e.g., increase in load carrying capacity and ductility, and construction considerations, e.g., economy and ease of application. Experimental results show a significant increase in the ultimate load capacity of all five strengthened slabs over the two control slabs. The FRC-strengthened slabs exhibit superior ductility and larger measured displacements than the GFRP-strengthened slab. The two methods are comparable in terms of ease of application but FRC is more cost-effective. Theoretical values, which are calculated using existing analytical methods, such as strain compatibility, yield-line analysis, and, as appropriate, flexural shear stress analysis, are generally in good agreement with experimental data. Furthermore, by modifying similar analytical methods for fiber-reinforced polymers (FRPs) found in the literature an analytical method is derived for FRC. The methodologies utilized here provide a means for analysis and design of such rehabilitation schemes. As a result of this study, it is concluded that FRC has great potential as a strengthening method, and future work is recommended to further optimize the proposed strengthening technique.