Durability Study Of Bfrp Bars And Their Reinforced Concrete Beam Immersed In Seawater

Basalt Fiber Reinforced Polymer(BFRP)bars,as a new type of composite materials,have been used in coastal projects by many countries to replace steel bars.BFRP bars possess high strength and alkali-resistance,they stay in seawater(SS)and sea sand(SC)environment without being rusted like steel bars,and to be seen as a substitute of steel bars used in future reinforced concrete structures.In view of investigating the properties of BFRP bars,bond strength between BFRP bars and concrete,and shear performance of BFRP bar reinforced concrete beam in seawater environment,the research work includes three following contents:1)Degradation of BFRP bars’ mechanical properties,including tensile property,flexural property,shear property and in-plane shear property.Samples include BFRP bars that immersed in simulated seawater with a temperature of 20°C/40°C/60°C;and wrapped in mortar immersed in simulated seawater with a temperature of 20°C have been tested.2)Bonding property of BFRP bars and SSSC concrete: Pull-out experiments of BFRP bar SSSC concrete and normal concrete immersed in seawater environment have been conducted.3)Degradation of BFRP bar reinforced concrete beam: Experiment of shear performance degradation of BFRP bar reinforced concrete beam has been conducted.Based on the experiments,the main results are listed as follow:1)The higher the temperature of sea water immersion,the less the bond of resin on the surface of the BFRP fiber,the more the tensile strength degrades.Compared with the non-encapsulated BFRP the BFRP bars encapsulated by the mortar are more obvious due to the strength degradation of the high internal alkalinity in the immersion sea water.2)Seawater in concrete have a corrosion effect on the matrix,causing friction between BFRP bars and concrete bond strength decreased.Sea water immersio n reduces the resin strength of the BFRP bars.3)The loading process of BFRP beam is divided into four stages: elastic stage,cracking stage,shear stress,failure stage.Load-deflection curve has a high rigidity stage in the beginning and then a low rigidity stage until failure,due to a sudden redistribution of stress after crack.