Influence Of Natural Exposure On Flexural Property Of FRP Rods And Concrete Beams Made Of Sea Water And Sea Sand

With the rapid process of urbanization,the scale of architectural engineering projects is constantly upgrading and expanding.As a consequence,the demand for concrete and construction sand is also increasing.In some regions,the demand for river sand has exceeded the supply.Regardless of environmental protection or economic perspective,the widespread exploitation of sea sand becomes an inevitable trend.Due to the high content of chloridion in sea sand,it may corrode the reinforcing steel bars and structures in the concrete,causing “sea sand houses”.If FRP rod is used to replace reinforcing steel bars in concrete,the abundant sea sand can be directly utilized without being processed in advance.It is quite important for resolving environmental crisis,eliminating corrosion and ineffectiveness of steel bars in sea water.At present,FRP rod concrete structures are most applied in exposed parts of bridges and highways.The research on durability of sea sand replacing river sand in harsh environment is stilled required.FRP resistance to chlorine salt corrosion is quite apparent.However,it is quite sensitive to significant changes in temperature,humidity and acid environment.Hence,this paper selects FRP rod rather than steel bar to apply in concrete structures of reinforcing rib without being processed by sea water desalination.In doing so,compression test on sea sand concrete,test on bending property of FRP rod and concrete beam with aging are conducted.Besides,it discusses the mechanical properties of sand concrete,analyzes changes in flexural property FRP rods and concrete beams with age.The paper will conduct test on flexural property of FRP rod and concrete beams that consist of two types of FRP rods(BFRP rods and GFRP rods),three types of concrete(common concrete,sea sand concrete,sea water and sand concrete),and three types of age(three months,six months and one year).It analyzes destruction patterns of FRP,concrete and different time periods on beam structures,failure mode,cracking load and flexural capacity.According to relevant experiments,the strain of concrete and FRP rods,deflection and crack widths of beams are determined.Research results indicate:(1)The increase of age will have a certain degree of weakening on the bending performance of most FRP reinforced concrete beams,mainly because the bending capacity and ultimate deflection decrease with the increase of age.However,the maximum crack width of the beam gradually decreases with the increase of age.The increase of the age will lead to the first cracking load of the FRPreinforced sea sand concrete beam rising and then decreasing,and the crack spacing gradually increasing;(2)short-term The ultimate deflection and cracking load of concrete beams are from large to small: sea sand seawater concrete beam> sea sand freshwater concrete beam>ordinary concrete beam;and the bending performance of FRP beam(such as bending capacity and Extreme deflection,etc.)tends to be more and more from large to small: ordinary concrete beam> sea sand freshwater concrete beam> seawater sea sand concrete beam.(3)Due to excellent strength of extension and elasticity modulus,ultimate load,deflection,compressive strain,fracture space of BFRP are greater than GFRP rods and concrete beams.The maximum crack width is lower than GFRP rods.Lastly,the paper consults the conclusions of existing literature,compares and analyzes computation results and test results.Moreover,it also aims to demonstrate whether formulations of bearing capacity,deflection and crack width in existing literature can be applied in concrete beams made of sea water and sand.