Experimental Study On Bond Behavior Between FRP Bars And Seawater And Sea-sand Concrete

Due to the scarcity of river sand,makes using sea sand and seawater as a hot topic and FRP bars tendon,the advent of the resistance to chlorine ion corrosion advantage makes it become one of the selection of alternative steel bars,but as a result of FRP bars tendon,especially basalt fiber reinforced polymer(BFRP)bars development use fixed number of year is not high,the need of BFRP bar and seawater sea sand concrete bonding performance further research.Therefore,it is of great practical significance to carry out research on the bond durability of BFRP bars and seawater sand concrete.In addition,FRP bars do not have strong ribs for bonding to concrete and may therefore have weaker bonding properties than steel bars.In order to overcome this problem,adding fiber and expansion agent to seawater sand concrete to strengthen the bond stress of FRP bars may be a feasible solution.In this thesis,through the accelerated aging test simulating the effect of sunshine temperature cycle,the experiment of mixing glass fiber and expansion agent in concrete and the theoretical calculation and analysis,the bond durability of BFRP bars and SSSC and the bonding enhancement method of FRP bars and SSSC were studied,including:(1)Firstly,the mechanical properties of seawater sand concrete were analyzed through different concrete strength grades,target temperatures and cycle times.The results show that the higher the strength,the better the compressive performance,but the more brittle concrete;When the target temperature reaches 100℃,the mechanical properties degrade seriously.And the experiment of 150 cycles has little effect on the mechanical properties of concrete;The stress-strain constitutive model of cylinder is established.Secondly,the bond durability between BFRP bars and sea water sand concrete is analyzed through different concrete strength grades,steel bar diameters,target temperatures and cycle times.The results show that the BFRP bars with a diameter of 10 mm have the best performance in this test.Moreover,with the increase of target temperature or cycle times,the bond strength and bond stiffness between BFRP bars and seawater sand concrete have a certain degree of degradation.Compared with the conditions,the bond stiffness decreases by up to 28%,and the bond strength decreases by up to 19%.(2)the effects of glass fibres and expansive agent on the bond behaviour of glass/basalt FRP bars cast in SSSC were studied by conducting pull-out tests with varying fibre content,fibre length,and expansive agent content.The results revealed that although the addition of glass fibres and/or the expansive agent significantly increases the bond stiffness,it only marginally increases the bond strength of the FRP bars.Overall,the addition of both fibres and the expansive agent offers certain synergistic effects;however,improving the bond strength is still difficult owing to the premature failure of the FRP bars.Finally,constitutive models to simulate the bond behaviour of FRP bars in SSSC were proposed.