Study On Mechanical Properties And Durability Of Basalt Fiber Reinforced Concrete

In recent years,study on the fracture mechanics in regard to durability of concrete has become an important topic in concrete technology in China.Especially,the freezethaw damage and the internal and external cracks of concrete expand will lead to loose internal structure and deteriorated.It will reduce the fracture performance and bending toughness of the material.Basalt fiber reinforced concrete(BFRC)is a new type of fiber reinforced concrete,which is made of high performance basalt fiber and concrete.More and more scholars use basalt fiber to improve the frost resistance of concrete.However,basalt fiber(BF),as an inorganic fiber,has good aging resistance compared with organic polypropylene fiber and polyacrylonitrile fiber,which will improve the cohesion and stability of concrete in the application of concrete,as well as improve the impact resistance of concrete,reduce its brittleness and improve the impermeability,freeze-thaw cycle resistance and shrinkage resistance of concrete.Therefore,it is of great significance to study the influence of BF on the mechanical properties and durability of concrete for expanding its application in the fields of port deep-water wharf,sea crossing bridge and severe cold area.In this paper,BF with 8 kinds of volume contents(0;0.05%;0.10%;0.15%;0.20%;0.25%;0.30%;0.35%)on the mechanical properties and durability of C30 concrete.The main research contents are as follows:Firstly,study on influence of different BFRC on the compressive strength,flexural strength,splitting tensile strength and early cracking resistance of concrete.It is found that BF has little effect on the improvement of compressive strength of concrete.The flexural strength and splitting tensile strength of basalt fiber concrete are better than that of plain concrete.Moreover,with the increase of volume fraction of BF,the flexural strength and splitting tensile strength of concrete tend to rise first and then decrease.Both them of the maximum strength are 0.30% of BF.There is no crack in the basalt fiber concrete within 3 days when the BF volume fractions is 0.25% ~ 0.35%.Secondly,the effect of different content of basalt fiber on the long-term durability of concrete,such as carbonation resistance and freeze-thaw resistance,was studied.The influence mechanism of BFRC was studied by pore structure analysis,and pattern features of the fibers were sorted with the observation of surface by scanning electron microscope(SEM).The results show that when the curing time of concrete are 7d and 28 d,the carbonation resistance of BFRC with fiber volume fractions 0.05% content is the best,and the carbonation resistance can be improved by adding BF content.The highest relative dynamic modulus and mass loss rate come from 0.30% BF.Adding BF can improve the freeze-thaw resistance of concrete.With the increase of BF content in a certain range,BF can reduce the total porosity and average pore size of concrete,optimize the pore structure,and improve the durability of basalt fiber concrete.Finally,the influence of different content of basalt fiber on the impact resistance of concrete was studied.It is found that the stress,failure load,absorption energy and energy density of basalt fiber reinforced concrete are all higher than those of plain concrete under dynamic impact load.HJC model can better simulate the stress-strain state of plain concrete under impact failure.The HJC model modified by coefficient has high fitting accuracy for the stress-strain state simulation of basalt fiber concrete.In the damage process simulation of basalt fiber concrete with the HJC model modified is found that the integrity of basalt fiber concrete is better than that of plain concrete when it is damaged by impact load.