<p>Gas suction during the concrete pumping process causes a transition from constant flow to unsteady flow, seriously compromising boom stability. Therefore, this study investigated the characteristics of unsteady flow in the different pipelines of a pump truck. Firstly, based on the C40 concrete properties, a pipeline fluid domain geometric model was established to verify the grid independence. Then, a three-phase flow mathematical model was constructed, including gas-liquid phase control equations, a solid particle motion equation, and a laminar flow model. Gas and liquid phase flows were simulated using Fluent, and the interaction between solid particles was simulated using Rocky. The flow characteristics of straight, elbow, and combined pipes were simulated using a coupling method of computational fluid dynamics (CFD) and discrete element method (DEM). Finally, a comparison is made based on numerical simulations of the effects of different pipeline structures and pumping parameters on concrete flow characteristics. The results indicate that increasing the gas volume fraction reduces pressure in both straight pipes and elbows, and decreases the excitation force in straight pipes. However, the excitation force in the elbow remains unchanged. Notably, the excitation force in the straight pipe peaks at a gas volume fraction of 30%. Increasing the attitude angle of the straight pipe raises the pressure but decreases the excitation force. Increasing the curvature radius of the elbow will increase the pressure, but it has little effect on the excitation force.</p> Graphical Abstract <p></p>