The microscopic fracture model for determining the fracture behavior of self-compacting lightweight concrete

Abstract

The fracture toughness (KIC) and tensile strength (ft) of concrete are critical parameters governing crack resistance. Concrete usually exhibits brittleness under flexure and tension, so this brittle fracture first occurs at the micro level. Many researchers have studied its fracture properties at the micro level. However, the theoretical model and calculation formulae do not reflect the influence of micro-material parameters on the corresponding fracture properties. In this paper, the microscopic fracture model of self-compacting lightweight aggregate concrete (SCLC) was developed, considering the parameters of micro-nano silica materials. First, the characteristic parameters, such as particle size, specific surface area, and unit weight of micro silica (MS) and colloidal nano-silica (CNS), were considered, and the calculation equation for fictitious crack growth length was proposed. Then, the micro-fracture model was developed, which was further used to calculate the fracture parameters KIC and ft of SCLC incorporated with micro-nano silica. The results are found to be consistent with the fracture parameters determined by the size effect model. In addition, the failure curves of different structural fracture modes of SCLC were established through the fracture parameters KIC and ft obtained from the microscopic fracture model, and the fracture modes of SCLC incorporated with MS and CNS were identified. The peak load of the minimum specimen size satisfying linear elastic fracture was also predicted. This research provides a new perspective for evaluating concrete fracture parameters, realizes the progressive prediction of concrete fracture performance from macro to micro, and fills in the research gaps in the existing knowledge base on the synergistic effect of MS and CNS to enhance the fracture performance of SCLC.