MECHANICAL PROPERTIES AND APPLICATION OF ARAMID FIBER REINFORCED CONCRETE

Abstract

Corrosion of reinforcement is one of the main cause of deterioration of reinforced concrete (RC) structures which affects the load carrying capacity and durability of structures. Aramid fibers are known as synthetic fibers that have excellent tensile strength and high corrosion resistance. The purposes of this study are to investigate the effect of the presence of fibers and fiber geometry on mechanical properties of aramid fiber reinforced concrete (ARFC) and to investigate the flexural behaviour of corroded RC beams which were repaired by aramid fiber reinforced mortar and mortar product in the market. To accomplish the first objective, compressive, splitting, and direct tensile tests were conducted. Plain concrete and five fiber types of aramid fiber reinforced concrete having the different shape and length were tested. Fiber lengths were 30, 40 and 50 mm. Fibers were single and twisted shape. The volume fraction of fibers was 1.0% in all AFRC mixes. Significant improvement of splitting tensile strength was observed with the presence of aramid fibers. Especially for direct tensile strength, aramid fibers could provide better post-cracking tensile resistance. The length and shape of aramid fibers strongly affect the tensile behaviour of AFRC. Forty millimeter is the proper fiber length to increase the tensile strength. Although the single shape fibers yields the highest peak tensile stress, twisted fibers can resist higher load in post-peak region. In the second part, four reinforced concrete beams were tested under four point bending. One beams was control beam without corrosion and three beams were corroded by accelerate corrosion to reach 10% mass loss of longitudinal reinforcement. Two corroded beams were repaired at the tensile zone by aramid fiber reinforced mortar (AFRM) and mortar product in the market. The aramid fibers used are 40-mm-twisted fibers. The results showed that the load capacity of the corroded RC beam repairing by AFRM was recovered to be close to the non-corroded RC beam. The width of cracks in corroded beam repairing by AFRM decreases significantly. However, the flexural capacity of corroded RC beams could not be recovered when it was repaired by mortar only. Finally, a model was suggested to predict the flexural capacity of beams. The predicted results from the model are found to agree well with test data obtained. It shows that the flexural capacity of beams can be suggested by the predict model accurately.