Research On The Compression Resistance Of Basalt Fiber Concrete After High Temperature-Water Cooling

With the rise of a large number of high-rise buildings and large-span public buildings in China,it is more and more difficult to evaluate and repair the safety of buildings after a fire.Therefore,there are higher requirements for the design of building structures and the performance of building materials.The concrete material is the most used material in building construction,so the requirements for its mechanical properties under high temperature environment have become higher and higher.This article takes the concrete structure repair and safety evaluation after building fire as the background.Through the compressive test of the basalt fiber concrete(BFRC)specimen under the coupling effect of different influencing factors(temperature,fiber content,confining pressure and loading rate),the stress-strain relationship curve is drawn to reveal the influence law of each influencing factor on the compressive properties of the fiber concrete.Introducing the Rock Engineering System(RES)theory,using an improved BP(Back propagation)neural network to establish a BFRC anti-stress performance prediction model under multi-factor coupling,and analyzing the interaction advantages and strengths of various influencing factors on the concrete anti-stress performance.The specific research conclusions obtained are as follows:(1)The appearance of the specimen before and after high temperature-water cooling had little effect with the change of the basalt fiber content,the temperature increased,the surface color of the specimen changed from blue-gray to off-white,the sound of tapping was more crisp,and the mass loss rate and volume growth rate continued to increase.(2)In the static test,the fiber reinforced concrete specimens showed confining pressure restraining enhancement effect,but such restraining reinforcement effect did not sho w obvious monotonicity.As the temperature increased,the static compressive properties of the fiber reinforced concrete specimens decreased significantly,showing a significant temperature damage softening effect.After mixing with basalt fiber,the static compressive properties of concrete specimens decreased slightly,but its plastic reinforcement effect was significant.(3)The confining pressure showed a non-monotonic restraint enhancement effect on the dynamic anti-stress performance of the BFRC specimen.As the heating temperature increased,the specimen exhibited a significant temperature damage softening effect under uniaxial action,but when different radial confining pressures were applied,the temperature was not strongly related to the dynamic anti-stress performance of the specimen.The effect of basalt fiber on the dynamic anti-compressive performance of the BFRC specimen under uniaxial action was not obvious,and the dynamic anti-compressive performance of the BFRC specimen was significantly improved under the confining pressure of 10 MPa.Depending on the temperature,the optimal dosage was 0.2% and 0.3%.The peak stress of the specimen increased with the increase of the loading rate,showing a significant strain rate strengthening effect.(4)Among the four factors that affect the dynamic compressive properties of BFRC materials,the impact strength from high to low was confining pressure,loading rate,temperature and basalt fiber content.Among them,confining pressure,loading rate and basalt fiber content had a positive effect on the improvement of concrete’s dynamic anti-stress performance,and temperature had a reverse effect.