Experimental and numerical study on the mechanical properties of limestone calcined clay cement concrete

Limestone calcined clay cement (LC3) is a new potential replacement for traditional cementitious materials. Although the strength and durability of LC3 concrete are confirmed to be prominent, not all aspects of the mechanical properties of LC3 concrete have been studied comprehensively, for example, uniaxial compressional stress–strain relationship. Numerical models and expressions of the uniaxial compressional stress–strain relationship proposed for ordinary Portland cement (OPC) concrete, which are based on experimental results, may not be suitable for LC3 concrete. In this study, the hydration process, pore structure, and mechanical properties of OPC and LC3 pastes and concretes with different water‐binder ratios are experimentally investigated. Based on the measurement results, the uniaxial compressional stress–strain curves of OPC and LC3 concretes are simulated by using a structural unit model. In the structural unit model, the uniaxial compressional stress–strain curve of concrete is divided into three stages, and each stage is simulated separately. The simulated uniaxial compressional stress–strain curves of OPC and LC3 concretes, by using the structural unit model, are compared with experimental results to evaluate the accuracy of the simulation. The experiment and simulation results indicate that there is less calcium hydroxide and more ettringite in LC3 paste compared with OPC paste with the same water‐binder ratio at the same curing age. The porosity of LC3 paste is higher while the microstructure of LC3 paste is finer compared with OPC paste with the same water‐binder ratio. Post‐peak ductility of LC3 concretes is better than that of OPC concrete. The trend of the uniaxial compressional stress–strain curves of OPC and LC3 concretes can be well predicted with the structural unit model.