Study On Energy Evolution And Damage Of Deformation And Failure Of Steel PVA Hybrid Fiber Reinforced Concrete Under Seawater Environment

Steel-pva hybrid fiber(SF-PVA)concrete,as a new composite material,has better mechanical properties than ordinary concrete,and has a broader application prospect in the field of civil engineering.At present,most of the research on steel-PVA hybrid fiber concrete focuses on its mechanical properties,while the research on corrosive environment such as seawater is relatively few.Concrete served in seawater environment will be subjected to harmful ions erosion,various properties will change.The deformation and failure of concrete is driven by energy,and the energy conversion and the evolution of characteristic stress points are the essential reasons for the change of concrete performance.Therefore,this thesis studies the energy evolution and damage characteristics of steel-PVA hybrid fiber concrete deformation and failure under seawater environment,in order to supplement and improve the application scenario of steel-PVA hybrid fiber concrete.The main work and research achievements of this thesis are as follows:(1)The incorporation ratio of steel-PVA blended fibers was determined by literature analysis.Based on the characteristics of seawater environment,seawater full immersion test and seawater dry and wet cycle test were used to simulate the concrete in seawater immersion area and seawater change area,respectively,to analyze the appearance characteristics of concrete after seawater erosion,and it was found that with the increase of immersion time,the exterior color of concrete became whiter.The microscopic products of concrete after seawater erosion were explored by SEM,and it was found that a large number of cracks appeared in the SEM diagram of seawater erosion for 56 days.(2)The compressive strength of concrete under different conditions was obtained through uniaxial compression test.The results show that SF1.5%-PVA0.15%can improve the compressive strength of concrete most obviously.In seawater environment,the compressive strength of concrete increases first and then decreases with the increase of erosion days.The addition of steel-PVA hybrid fiber can effectively weaken the erosion effect of seawater on concrete.In the seawater immersion area,the concrete compressive strength of SF0.5%-PVA0.15%,SF1.5%-PVA0.2%,SF1%PVA0.1%is least affected by seawater.In the seawater fluctuation zone,the compressive strength of concrete with SF0.5%-PvA 0.1%is least affected by seawater.(3)The energy evolution law of steel-PVA hybrid fiber concrete in the process of deformation and failure in seawater environment is analyzed and summarized,as well as the change law of the dissipated energy at the crack closure point,the dissipated energy at the peak stress and the elastic energy index at the peak stress.The dissipated energy at the closure point of common concrete cracks increases first,then decreases and then increases with the increase of the days of seawater erosion.In the seawater immersion zone,the dissipated energy at the peak stress first decreases and then increases with the increase of erosion days,while in the seawater change zone,the dissipated energy alternately decreases and increases.The elastic energy index at the peak stress increases first and then decreases with the increase of erosion days in the seawater immersion zone,while the elastic energy index at the peak stress increases and then decreases with the increase of erosion days in the seawater fluctuation zone.The addition of steel-PVA hybrid fiber can effectively reduce the erosion effect of seawater on concrete.The comprehensive analysis shows that SF1%-PVA0.15%concrete specimens are less affected by seawater in each energy index.(4)The influences of different seawater environment,different erosion days and different hybrid fiber ratio on the initial damage variables of concrete were studied.The variation law of the development velocity of damage variable curve during concrete compression is analyzed.In the seawater immersion zone,the development speed of the initial damage variable and the damage variable of ordinary concrete firstly increased and then decreased with the increase of the days of seawater erosion,while in the seawater change zone,the development speed of the initial damage variable and the damage variable increased and then decreased.During the test period,the initial damage variables of concrete with fiber ratio of SF1%-PVA0.15%and SF1%-PVA0.2%are negative.In the seawater immersion zone,the damage variable development rate of SF1%-PVA0.15%is less affected by seawater,while in the seawater change zone,the damage variable development rate of SF0.5%-PVA0.15%is least affected by seawater.