Study On Durability Of Hybrid Fiber Reinforced Concrete In Marine Environment

With the continuous advancement of the global economy,the marine economy has gradually become a strategic field that has attracted widespread attention from all countries.Amid this trend,many countries have clearly placed it at the center of their development plans.However,under the harsh conditions of the marine environment,marine structures face many problems and challenges.Fiber concrete has excellent properties and has been widely used in the field of marine engineering in recent years.At present,steel fiber reinforced concrete is still dominant in fiber reinforced concrete,but steel fiber reinforced concrete is susceptible to corrosion and chloride ion erosion in marine environments,thereby affecting the life and aesthetics of structures.In contrast,basalt fiber concrete has strong corrosion resistance and chloride ion erosion resistance,and can be used stably for a long time in the marine environment.At present,the structural basalt fibers developed by relevant scholars have been proved to be able to effectively resist and inhibit the macroscopic cracks of concrete and improve the flexural toughness of concrete.However,when used alone,the performance improvement of concrete is limited.It can inhibit the formation and development of early micro-cracks in concrete,and can also improve the ability of concrete to limit macro-cracks after cracking.In this paper,the short-term mechanical properties of cross-scale hybrid fiber concrete and the durability performance under seawater dry-wet cycles are studied.The specific research contents are as follows:(1)The compressive performance test and four-point flexural performance test were carried out on the concrete cured for 28 days,and the effects of twisted basalt fiber content,non-structural basalt fiber and structural fiber types on the short-term mechanical properties of cross-scale hybrid fiber concrete were studied.Influence.The test results show that the incorporation of structural fibers changes the concrete from brittle failure to ductile failure and improves the flexural toughness of concrete.the compressive strength of hybrid fiber concrete decreases first and then increases with the increase of twisted basalt fiber content,while With the increase of non-structural basalt fiber content,it showed a trend of first increasing and then decreasing.compared with single-doped twisted basalt fiber,mixing 0.2%non-structural basalt fiber can effectively improve the flexural performance and compressive performance of concrete.However,mixing 0.4% non-structural basalt fiber will produce a negative mixing effect.when the content of twisted basalt fiber is1.5%,the peak strength and equivalent residual strength of concrete after cracking are higher than that of 1.0%,and the end hook steel Fiber exhibits the best flexural properties.(2)The seawater dry-wet cycle erosion test was carried out on the hybrid fiber concrete.The corrosion ages were set to 30 d,60d,90 d,and 120 d respectively.A total of 108 freshwater-mixed concrete cube compression test pieces and 108freshwater-mixed prepared concrete prism flexural specimens.The study found that the debonding of structural basalt fiber resin matrix and basalt fiber filaments is an important reason for the degradation of the compressive and flexural properties of concrete mixed with structural basalt fibers.the relative dynamic elastic modulus of steel fiber concrete specimens in the late corrosion period The decrease is even greater.mixing 0.2% non-structural basalt fiber can improve the corrosion resistance of concrete,but mixing 0.4% non-structural basalt fiber will lead to worse durability.seawater corrosion of steel fiber in short-term corrosion does not Not serious,the flexural performance of steel-nonstructural basalt hybrid fiber reinforced concrete decreased slightly after corrosion.(3)The corrosion test of hybrid fiber seawater concrete under seawater dry-wet cycle was carried out,and the influence of mixing water on the durability of cross-scale hybrid fiber concrete was studied.72 cubic compression specimens mixed with seawater and 72 Flexural specimens mixed with seawater.The research results show that: without corrosion,the compressive strength of concrete mixed with seawater is slightly lower.after corrosion,the strength retention rate of the specimen group mixed with twisted basalt fibers mixed with seawater is slightly lower than that of concrete mixed with fresh water.Under the corrosion of time,the mixing water will basically not affect the flexural properties of the end-hook steel-non-structural basalt hybrid fiber concrete,but it will affect the peak strength retention rate after cracking of the straight steel-non-structural basalt hybrid fiber concrete.The effective residual strength retention rate has a great influence.