The Mechanical Properties And Damage Assessments Of Basalt Fiber Reactive Powder Concrete

Reactive powder concrete(RPC)is a kind of high-performance concrete with high strength,good durability and good stability,which is developed in the 1990 s.It is characterized by improving the uniformity of matrix by eliminating coarse aggregate and improving the compactness of matrix by optimizing mixed particle gradation.Silicon-containing materials such as silica fume and fly ash are commonly added to RPC as the active ingredient.However,as the strength increased,so did the brittleness of RPC.To alleviate this problem,fibers are often added to enhance toughness.Basalt fiber is an environmentally friendly material made from natural basalt ore.In recent years,basalt fiber has been widely used in concrete reinforcement due to its excellent mechanical properties,corrosion resistance,high temperature resistance and electrical insulation.The damage of concrete material includes matrix cracking and fiber drawing fracture.If the fracture process and cracking mode of concrete can be determined,the structure can be strengthened by proper design to enhance the resistance to specific fracture mode.At the same time,it will be able to give early warning of an eventual fracture.Currently,a technique called acoustic emission(AE)has shown great potential for real-time monitoring and assessment of material damage.Acoustic emission(AE)technology is a non-destructive testing technology with high sensitivity and full cycle on-line monitoring.In recent years,AE technology has been widely applied in such construction fields as crack monitoring and damage assessment of reinforced concrete beams,shear walls and short walls.Based on the development and reform commission of Jilin province project "basalt fiber active powder composite modified concrete performance evaluation and structural design method research".Response surface method(RSM)was used to evaluate the influence of four mixing ratio parameters of basalt fiber activated powder concrete(BFRPC)on its performance and mechanical properties.The damage process of reactive powder concrete under uniaxial compression was analyzed by acoustic emission technique.The specific work is as follows:(1)The fluidity,bending strength and compressive strength of BFRPC were tested and evaluated by response surface design.The statistical experimental model shows that the silica fume/cement ratio is the main factor affecting the performance of BFRPC.When D = 0.2,the increase of basalt fiber content has a significant effect on the increase of bending and compressive strength.The addition of basalt fiber significantly improved the mechanical properties of RPC.D=0.3 is the critical value of admixture.When D = 0.4,the reduction of fiber content and the increase of quartz sand content can improve the compressive strength.(2)Based on optimizing the mixture ratio design,selection of doped fiber,basalt fiber,steel fiber in the three groups of specimens,prism uniaxial compression test,discuss the different fiber type on the basic mechanical properties of reactive powder concrete under uniaxial compression,through the analysis of mechanical parameters,shows that the join of basalt fiber can be on the basis of increased the strength of specimen effectively increase its toughness.(3)Based on the damage analysis of stress-strain mechanics,the influence of fiber incorporation on the damage pattern of specimens was analyzed by comparing with the results of acoustic emission nondestructive testing.The failure stage and failure mode of the specimen were determined by acoustic emission parameters.For fracture characteristics,fiber content was found to be an important determinant,and the key AE parameters,such as hits,energy and amplitude were found to be related to the damage stage of the specimen.During loading process,the rise angle(RA)and the average frequency(AF)show opposite trends,and their changes are related to the fracture mode of BFRPC.(4)The b-value analysis method is used to process the acoustic emission parameters and further determine the early warning value of the damage stage of reactive powder concrete,so as to provide a reference standard for the occurrence of severe damage cracks in reactive powder concrete.