Study of Mechanical Properties and Constitutive Relationship of ES-UHPC under Uniaxial Tension

Early-strength ultrahigh performance concrete (ES-UHPC) is used widely in road repair, as well as in emergency rescue and disaster relief operations. Previous studies focused primarily on the mechanical properties of ordinary ultrahigh performance concrete, and there are few studies of ES-UHPC. On the basis of the successful research and development of ES-UHPC, this paper selected 24 groups of dog-bone specimens for uniaxial tensile tests. The failure mode, elastic modulus, and peak strain of all the specimens were analyzed using the acoustic emission (AE) technique, and the ES-UHPC at different ages under uniaxial tension was studied. The results showed that the 1-day tensile strength of ES-UHPC reached 4.61 MPa, the tensile elastic modulus reached 28.401 GPa, and the cube compressive strength was 66.81 MPa, which exceeds that of the ordinary UHPC. The descending segments of the axial tensile stress–strain curves for specimens at ages of 3 and 7 days were notably pronounced, which suggests relatively low ductility. Additionally, the early-strength agent had limited influence on strength development during the later stages. The 28-day tensile strength and cube compressive strength of ES-UHPC were 9.13 and 151.28 MPa, respectively, indicating that the early-strength agent did not compromise the long-term strength of the specimens. Based on AE, a damage mechanism analysis and constitutive relation study of ES-UHPC were conducted. The constitutive relations of the axial tensile behavior of ES-UHPC at various curing ages were established through regression analysis, and subsequently validated using comparative evaluation against existing empirical models. This enhanced formulation enables more-accurate simulation of age-dependent stress distribution in structural components. The research achievements of this paper provide a reference for the large-scale application of ES-UHPC.