Two Reinforced concrete one-way slabs with the cross section of 0.10 m x 0.63 m and 2.4 m span length were designed for the live load of 400 kg/m2. One of them was then strengthened according to ACI 318-05 with the 6 layers of CFRP to increase the live load resistance to 800 kg/m2 aiming to fail by CFRP debonding at low ductility range or with the flexural strength reduction factor, , of 0.76 . Third point loading test showed the debonding failure at the interface of CFRP and concrete during yielding of the
rebars. The load carrying capacity of strengthen slab was less than predicted ultimate capacity. The maximum tensile strain of outermost carbon fiber sheet was 0.001371 which is also lower than expected standard value. The evaluation of the flexural strength reduction factor, , based on the ultimate strain of rebar is 0.75. The test results showed that CFRP slab strengthening in case of very low ductility may be
hardly controlling failure behavior. The proper installation of strengthening system must be conducted under close supervision of licensed engineers and more research in this topic is needed.