Experimental Study On The Static-dynamic Properties And Microscopic Characteristics Of Coir Fiber Foamed Concrete

Nowadays,there are frequent traffic accidents under high-speed driving on expressways,and the driving safety of passengers and passengers is seriously threatened.In order to ensure safe driving requirements,the protection performance of infrastructure is also getting higher and higher.At present,although the traditional highway anti-collision facilities are sturdy and durable,they have the disadvantage of poor buffering and energy absorption performance,so this subject has developed a new type of foam concrete filled rubber tube anti-collision guardrail.The guardrail uses foam concrete as a filling material to increase the buffer energy absorption performance of the structure,but the foam concrete has low strength,high brittleness and easy cracking,which affects the integrity of the structure and the buffer energy absorption effect.The addition of fibers to the foam concrete can increase strength,increase toughness,suppress crack development,and increase the energy absorption capacity of the buffer.Commonly used inorganic fibers have higher energy consumption,and organic synthetic fibers have higher production process requirements.Although common organic fibers such as paper fibers,cotton stalk fibers,and straw fibers are environmentally friendly and low in energy consumption,they have poor strength and toughness.Coir fiber(Coir Fiber,CF)is a natural material with high tensile strength,good toughness,environmental protection,low energy consumption,toughening and toughening,which is used in foam concrete to suppress foam concrete cracking and improve its buffering energy absorption performance.In this paper,the effect of coconut fiber content on the mechanical properties and microscopic properties of foam concrete is studied.The main contents are as follows.First,through the static compression mechanical properties test,the failure mode,compressive strength,stress-strain curve and static compression energy consumption of coconut fiber foam concrete were studied.Studies have shown that the compressive strength,elastic modulus,plasticity and static energy dissipation capacity of coconut fiber after blending are better than those of foam concrete without fiber blending.As the fiber content increases,the plasticity of the foam concrete increases,and the compressive strength,elastic modulus,peak stress,residual stress,and energy dissipation capacity increase first and then decrease.Secondly,through the three-point bending mechanical property test,the failure mode,flexural strength,load-deflection curve and bending toughness of coconut fiber foam concrete were studied.Studies have shown that the flexural strength,stiffness,plasticity,bending capacity and bending toughness of coconut fiber after blending are better than those without fiber blending.As the fiber content increases,the plasticity of the foam concrete increases,and the flexural strength,stiffness,bending capacity,and bending toughness all increase first and then decrease.Then,on the basis of static experiment,dynamic compression mechanical performance test was carried out by Split Hopkinson Pressure Bar(SHPB),and the coconut under three air pressures(0.2MPa,0.25 MPa,0.3MPa)was studied.The failure mode,dynamic compression strength,dynamic factor DIF,dynamic compression stress-strain curve and dynamic compression energy dissipation performance of fiber reinforced concrete.The research shows that the dynamic compressive strength,stress platform,and dynamic compression energy consumption of coconut fiber foam concrete increase with the increase of air pressure,and have a typical strain rate effect.Under the same air pressure,the dynamic compressive strength,dynamic factor,stress platform range,and dynamic compression energy consumption increase with a certain degree of increase after the coconut fiber content increases,and then decrease after a certain increase.Finally,in order to investigate the effect of different coconut fiber content on the microstructure and pore structure of foamed concrete,the morphology,porosity and average pore size of the pore structure of coconut fiber foamed concrete using image processing software(Image-pro plus,IPP)software The roundness value was analyzed,and the foam was observed by Scanning Electron Microscope(SEM),Energy Dispersive Spectrometer(EDS)and X-ray Diffraction(XRD)Concrete structure morphology,the microstructure morphology,element energy spectrum and hydration composition of the specimen were analyzed.The research shows that with the increase of the fiber content,the porosity and the average pore diameter decrease first and then tend to be stable,and the roundness value decreases first and then increases.With the increase of fiber content,the hole breaking phenomenon of foam concrete has been reduced to a certain extent,the gap between the fiber and concrete bonding interface is small,the hydration process of Calcium Silicate Hydrate(C-S-H)gel is slowed,and the hydration product No significant changes.