Flexural Fatigue Behaviour Of Aligned Steel Fiber Reinforced Cementitious Composites

Steel fiber reinforced cementitious composites(SFRC)have been widely applied in various fields,such as pavement,bridge deck,tunnel engineering and hydraulic engineering.Steel fiber plays a significant role in crack resisting,strengthening and toughening.The tensile property,crack resistance ability and the fatigue behaviour of SFRC are enhanced.Steel fibers,which orientated to the direction of tensile stress have the maximum reinforcement effect.However,one of the main limitation of SFRC is that fibers are randomly distributed so that many fibers are not fully functioned.Previous studies of aligned steel fiber reinforced cementitious composites(ASFRC)focused on the static mechanical properties,of which the results revealed a superior improvement over randomly distributed steel fiber reinforced cementitious composites.It is a reasonable assumption that the aligned steel fiber also contributes to fatigue performance.The flexural fatigue behaviour of aligned steel fiber reinforced cementitious composites are studied based on the three-point bending fatigue experiment,which is of engineering practical significance for better and safer application of this material.First,based on the three-point bending static test of SFRC and ASFRC specimens,the influence of steel fiber direction was analyzed.Results showed that ASFRC specimens had greatly increased flexural strength and flexural toughness.Secondly,the influence of steel fiber orientation distribution on flexural behaviour was investigated based on three-point bending fatigue experiment.The flexural fatigue load performed on ASFRC and SFRC specimens were on the same.The fatigue life of ASFRC was significantly prolonged compared with SFRC,which indicated the crack resistance effect of aligned fiber was increased.Then the three-point bending fatigue experiments under different stress level were conducted.Results demonstrated that the aligned steel fibers contributed to the flexural fatigue behaviour so that the fatigue life and mid-span deflection of ASFRC were increased,especially under relatively low stress level.Finally,the Weibull distribution and the lognormal distribution were used to analyze the fatigue life of ASFRC and SFRC.The double logarithmic fatigue equations considering different survival rates were calculated.A modified fatigue equation was given considering the influence of steel fiber orientation distribution and the volume fraction.The acoustic emission method was used and its signal was analyzed.Results indicated that aligned steel fibers existed obvious crack resisting dominance.