Study On Mechanical Properties Of Pva Fiber Reinforced Seawater And Sea Sand Cement-based Composites

With the rapid development of the construction industry,the world is facing the risk of shortage of river sand and fresh water resources,so the exploitation of new construction raw materials has become an inevitable trend of the construction industry.China is rich in sea water and sand resources.However,because there are many ions that can corrode metal in sea water and sea sand,the durability of reinforced concrete is easy to be affected by using them directly.PVA fiber has the advantages of strong corrosion resistance,low cost and high toughness,which can improve the corrosion resistance and seismic performance of reinforced concrete structure in marine environment.However,its mechanical properties and durability are unknown in the sea sand environment.Therefore,it is necessary to study the influence of sea water sand on its mechanical properties and durability.Firstly,considering different seawater concentration and age,three kinds of marine sand cement-based composite materials with PVA content were used to test the compressive strength of cube.The test results show that: the addition of fiber will change the failure mode of the specimens,1.5% fiber content can make the compressive specimens have better crack resistance;the compressive strength of the specimens increases with the increase of age.The results show that the compressive strength of the specimens decreases when the concentration of seawater is one time,and increases obviously when the concentration of seawater is three times.The compressive strength of C50 specimen can be greatly improved only when the fiber content is 1.5% and the seawater concentration is 3 times.Secondly,the bending behavior of the material are studied.The results show that the harmful ions in seawater and sea sand have a great influence on “the bridging effect” of the fiber.With the increase of seawater concentration,the bending strengthening ability of 0.75% fiber content flexural specimens is weaker than that of1.5% fiber content flexural specimens after 28 day.With the increase of the period,the bending softening phenomenon appears in low fiber content flexural specimens,and the strain hardening ability of high fiber content flexural specimens is further weakened.The bending toughness and durability of C30 specimens are stable,while the bending toughness and durability of C50 specimens are poor at the later stage of force bearing when the fiber content is 1.5%,so it is necessary to further improve the fiber content.Then,under the microscopic observation of the fiber corrosion of 180 day old specimens through SEM test,it is found that the surface of the fiber is smooth and there is no obvious corrosion phenomenon,which indicates that the seawater and sea sand environment does not affect the use of PVA fiber.Finally,according to the experimental data,the relationship between compressive strength,flexural strength and their corresponding deflection and flexural toughness index is established,and the calculation model of flexural toughness index about age,seawater concentration and matrix strength is given.The model has a good correlation.