Micro-mechanics Research on Tensile Mechanical Behavior of UHPC Specimen

The tensile behavior of ultra-high-performance concrete (UHPC) directly affects the crack resistance and durability of a structure. Thus, it is an important index. Based on an analysis of the cooperation between steel fiber and surrounding cement base, a mesomechanics tensile behavior model was established to study the tensile properties of a tensile UHPC structure before cracking. The random distribution of the steel fiber was considered to be the normal distribution, and the fiber force was considered to be the reactive force loaded by the cement base. A mechanical behavior prediction model was established to predict the mechanical behavior of the tensile UHPC in the elastic and pull-out stages based on the mesomechanics tensile behavior model. Pure bending specimens were tested to obtain the mechanical index, and the tensile behaviors at the elastic and pull-out stages were compared with those of the previously mentioned model. Moreover, the applicability of the mesomechanics tensile behavior model was verified using other reference data. The results showed that the working mechanism of the inner steel fiber could be described by the mesomechanics tensile behavior model before cracking. The bending test results of the UHPC at the elastic and pull-out stages agreed well with the theoretical values. The tensile behavior of the UHPC was dominated by the inner steel fiber, and the contribution of the cement base could be ignored to simplify the calculation and security. A bilinear tensile constitutive model was proposed, where the limit of the elastic stage was 180×10-6, and the minimum test value of 1 042×10-6 was taken as the limit of the pull-out stage. © 2021, Editorial Department of China Journal of Highway and Transport. All right reserved.