Monitoring and modeling the damage evolution in engineered cementitious composites subjected to sulfate attack through continuous ultrasonic measurements

Abstract The present research aimed to investigate the compressive response and damage evolution of engineered cementitious composites (ECC) subjected to sulfate drying-wetting cycles by using ultrasonic methods. The primary and shear wave (P- and S-wave) velocities, and a characteristic voltage energy (CVE) parameter were continuously measured during the drying-wetting cyclic tests and loading process. It was shown that the initial wave velocities stayed almost unchanged at the first 6 drying-wetting cycles (90d erosion), but followed by a sudden drop which communicated noticeable degradation due to sulfate attack. The evolution of wave velocities during compression revealed the conversion of failure mode from unstable failure to moderate failure, as erosion cycles extended. More importantly, the CVE curves functioned sensitively to the variation of stress-strain curve, which allowed delicate delineation of the underlying damage evolution of ECC after different degradation degrees. Based on the experimental results, a two-stage damage degradation model describing the degradation degree of ECC due to sulfate attack was established. Furthermore, a damage constitutive model that directly characterized by the evolution of ultrasonic parameters was proposed to predict the stress-strain curves of ECC under sulfate drying-wetting cycles. The damage model agreed well with the test data, and precisely reflected the failure characteristics of ECC in uniaxial compression.