Behavior Of Concrete Members Strengthened With Basalt Fiber Reinforced Plastic Sheets Under Freeze-thaw Environment

The concrete is the leading material of civil engineering. In the north of China, concrete frostbited because of low temperature which caused the durability of concrete structure becomes the focus now. At the same time, the question for lower concrete intensity caused by durability degeneration in the old building which needs to be strengthened is also loomed large.In the 20th centuty, the method of strengthening concrete structure with fiber reinforced plastic is developed quickly in the field of civil engineering. Fiber reinforced plastic (where briefed as FRP) is an ideal new composite material because of its lightweight, high strength and resistance to corrosion. With application widely used of FRP, the factors influenced the strengthend effects such as environment and the lower concrete intensity should be concerned, so study on durability of concrete structures strengthened with FRP is significant. Many scholars have been made large amount of experimental studies on mechanics porperties and durability for strengthening R.C. structure with CFRPand GFRP, on the contrary, few test was found for strengthening members with BFRP.In this paper, slow freeze-thaw tests were carried out for BFRP sheets and RESIN, the tensile strength, modulus of elasticity, coefficient of elongnation, cohensive strength between BFRP and concrete cubic specimen were analyzed under different cycles of freeze-thaw, the experimental researches on the flexural behaviors of concrete beams strengthened with BFRP under the enviroment of freeze-thaw were also carried out, the bearing capacity formulary was given at last according to debonding failure in the test, the main studies in this paper were shown as follows:1. The slow freeze-thaw tests were carried out for 0, 50, 100 times to fifteen BFRP specimens and fifteen resin specimens, which focused on tensile strength, modulus of elasticity, coefficient of elongation and cohensive strength.2. The slow freeze-thaw tests were carried out for 0, 25, 50, 75 times to sixty concrete cubic specimens, which focused on the cohensive performance between BFRP and concrete specimens. 3. Forty-five concret beams were fabricated, which divided into three teams according to the concrete strength. The crack loading, ultimate bearing capacities, taken into account the parametes with different cycle of freeze-thaw, concrete strength and different strengthing methods, models of failure were analyzed4. The flexural behaviors of concrete beam strengthened with BFRP were studied; three familiar calculation methods were introduced. The ultimate bearing capacity formula of debonding failure was presented according to the record of tests; the numerical calculations match a good need with the experiment results, which can be a good refrence for the same project when needs theoretical guidance.