Flexural fatigue behavior of hybrid nature fiber reinforced lightweight high-strength concrete

Lightweight high-strength concrete engineering structures have low dead weight and high seismic performance, but the brittleness is greater than that of traditional concrete. The inherent brittleness is bound to pose significant challenges for engineering applications. Based on the strategy of developing and improving the toughness of lightweight aggregate high-strength concrete, and unleashing the full potential of lightweight high-strength concrete in safer and more reliable structural applications, the study used ceramic particles as lightweight aggregates, mixed with basalt fibers and cellulose fibers to produce hybrid nature fiber reinforced lightweight high-strength concrete. By four-point flexural and fatigue tests, the flexural toughness and fatigue characteristics of the single/mixed nature fiber reinforced lightweight high-strength concrete under different stress levels were studied. And the fatigue life performance rules under different stress ratios were revealed, and the fatigue life equations were established with the two-parameters S-N(stress level-fatigue life) curve, considering the failure probability. The results show that under different stress levels, the fatigue life of all samples follows the two-parameter Weibull distribution probability model. The improvement of fatigue life of lightweight high-strength concrete with mixed fiber is better than that with single fiber, with the longest stable development duration and fatigue life. The fatigue strain evolution process of lightweight high-strength concrete with different fiber conforms to the development law of the third-order strain curve. The established fatigue life equation can be used to predict the flexural fatigue performance of fiber reinforced lightweight high-strength concrete under different stress levels. The improvement of fatigue toughness and service life has transformed lightweight high-strength concrete from "high strength but brittle" to "high strength and durability" and is expected to become an ideal material in earthquake engineering that combines lightweight, seismic performance, and sustainability.