Experimental Research On Compression Fatigue Properties Of High Ductile Fiber Concrete After Freeze-thaw And Sulfate Corrosion

As a construction material of the infrastructure construction, concrete is widely used around the world. Fatigue failure is a latent danger in construction engineering, traffic engineering, and offshore engineering. Previous researches have shown that concrete under fatigue loads has more obvious brittle failure characteristics than under static load. High ductility fiber concrete (HDFC) is a new kind of composite material, which is based on the engineering cement composite (ECC) proposed by Professor Li. of University of Michigan and developed by Shaanxi local materials. HDFC exhibits significant strain hardening behavior and multiple cracking pattern, which is beneficial to improve the fatigue performance of concrete.To study the compression fatigue performance of HDFC, a series of experiments with constant amplitude were designed, the fatigue life, deformation capacity,the influence of loading frequency and p-S-N equation of high ductile fiber concrete were investigated. Taking into account the environmental factors is one of the main reasons for the failure of concrete structures, the effect of sulfate corrosion and freeze-thaw damage on the fatigue performance of HDFC was studied.Under uniaxial compression fatigue loading, the specimens in fatigue failure still have good integrity and show more ductility at failure. Compression S-N curve of HDFC was obtained from compression fatigue test under different stress level and compressive fatigue strength is 0.679, the result is higher than ordinary concrete and steel fiber reinforced concrete.With the decrease of loading frequency, the fatigue life of HDFC was lower. The fatigue life of HDFC specimens obeys two-parameter Weibull distribution and the corresponding relationship between fatigue life and failure probability was given. When the probability of failure p is given,the corresponding fatigue life N at certain stress level S could be calculated. The results of this investigation could be proposed for potential application of HDFC.After 150 times of sulfate attack and dry wet cycles, the corrosion state of HDFC is not obvious, the compressive strength can reach to 81%, and the corrosion resistance is good.However, in the fatigue test, the internal defects of concrete caused by sulfate corrosion will accelerate accumulating fatigue damage. The higher the stress level, the more significant the impact. When the frequency is small, the influence of sulfate corrosion on fatigue life is larger.The average mass loss rates of the two groups were 75 and 150 times, respectively, and the average mass loss rate of the specimens was about 1%. The surface of the samples became rough, and the surface layer of the gel was peeled off in varying degrees. Again loading fatigue load HDFC fatigue times were significantly reduced at high stress levels, on the other hand, the effect of freeze-thaw cycles on the HDFC fatigue life is also significant.