Effect of water saturation on uniaxial constant amplitude tensile fatigue performance of ECC and its statistical analysis of fatigue life

The degree of water saturation has a significant influence on the tensile fatigue properties of Engineered Cementitious Composites (ECC). The half-saturated and saturated state ECC can be rapidly prepared by a vacuum saturation equipment. The fatigue tensile mechanical tests under five tensile stress levels and corresponding studies on the damage morphology, fatigue life, S-N relationship, fatigue strain and fatigue damage on dry, half-saturated, and saturarted state were conducted. The mathematical and statistical analysis method was also utilized to predict ECC’s fatigue life and strength with high confidence and high reliability, providing a reference for assessing structural safety. The study found that free water significantly reduces ECC fatigue strength, with fatigue life decreasing as water content increases. At 2 million cycles, fatigue strength reduction coefficients for 0%, 50%, and 100% water saturation are 0.623, 0.550, and 0.423, respectively. The three-parameter Weibull distribution best describes ECC fatigue life. Using this model, S-N and P-S-N curves were developed, incorporating confidence limits to derive γ-P-S-N relationships, ensuring high confidence and reliability.