Flexural Strengthening of Continuous RC Beams Using HPFRCC Precast Laminates

In this study, the use of precast laminates, made of high-performance fiber-reinforced cementitious composite (HPFRCC), was investigated for strengthening of continuous reinforced concrete (RC) beams. HPFRCCs are characterized by their high tensile strength and remarkable durability properties. To find the effect of strengthening, eight continuous (two-bay) RC beams were tested under monotonic load in the middle of spans; two of which were the control specimens and six of which were strengthened specimens. The HPFRCC laminates were prefabricated with 25 mm thickness and bonded to the tensile surface of beams using epoxy and mechanical anchorage. The longitudinal bars were added to laminates in four specimens to survey their effect on strengthened beams. Comparison of results declared that the load carrying capacity was increased up to 59 % in strengthened beams.  Ductility index of the strengthened beams was acceptable, and also up to 35 % growth in energy-absorption capacity was observed. Applying laminates to the tensile surface delayed crack propagation and decreased the midspan deflection. Also, stiffness of specimens in the cracked concrete stage was increased up to 78 % that led to decrease the service deflection. It is concluded that the use of HPFRCC laminates, especially in case of applying longitudinal bars, is an efficient method to enhance the flexural capacity of continuous RC beams.