Study On The Performance Of BFRP Rebar At Elevated Temperature

Basalt Fiber Reinforced Polymer (BFRP) rebar possesses the advantages of high-strength and alkali-resistance, which has emerged as a practical alternative for steel reinforcing bar for concrete structures. BFRP rebar has only been applied for less than two decade. The lack of knowledeges of the performances of BFRP rebar in various extreme environmental conditions, especially the performance of BFRP rebar at elevated temperatures, blocks the wide application in practice. In view of this, the performances of BFRP rebar at elevated temperatures were studied in the current work. Base on the experimental results, the behavior of BFRP bar reinforced concrete structures at elevated temperature is studied with numerical simulation. The research work mainly includes the following contents.1. Mechanical and thermal properties of BFRP rebar, including tensile strength and modulus, the bond strength between BFRP rebar and concrete, and the glass transition temperature have been tested. Based on the testing results, the recommended design values of BFRP rebar is proposed according to ACI.4402. The variation of tensile strength and stiffness of bare basalt fibers with temperature has been studied through the fiber bundle testing. The testing result shows that basalt fibers perform much better than glass fiber and aramid fiber at elevated temperatures. Besides the temperature limitation of basalt fibers is proposed accordingly.3. The tensile strength and stiffness of BFRP rebar was studied at various testing temperatures. Due to the heat insulation property of basalt fiber, BFRP rebar display better heat-resistance than CFRP and GFRP rebar, which is confirmed by the experimental results. Beside, the durability of BFRP rebar at elevated temperature was studied through testing the residual strength of heat treated BFRP rebar.4. On the basis of the mechanical properties of BFRP rebar at elevated temperatures, the elevated temperature behaviors of concrete beam and slab members incorporated with BFRP rebar are studied by finite element analogy. The result shows that the members cannot meet the requirement of fire resistance if there is no fire insulation protection. The relation between the thickness of fire insulation and fire resistance period of concrete members is analyzed by FEM.