The coarse aggregate–mortar interface transition zone (ITZ) has a great influence on the mechanical properties of concrete, which cannot be easily studied using laboratory tests in the mesoscale. In this paper, a series of axial compression tests were conducted using the discrete element method (DEM) on concrete specimens for four phases: coarse aggregates, mortars, aggregate–mortar interface transition zones, and voids. The effects of ITZ strength on macroscopic stress and microscopic cracks under different strength reduction factors were investigated through axial compression testing. With the increase in interface transition strength, the compressive strength of the concrete becomes stronger; moreover, the number of cracks decreases, and the anisotropy of contact orientation becomes weaker. Meanwhile, the direction of crack development and the damage mode of compressed concrete specimens were also dependent on the coarse aggregate–mortar interface strength coefficient.

In order to solve the problem that the built-in parallel bond model in the discrete element software cannot adequately simulate the post-peak fracture behavior of quasi-brittle materials, a linear cohesive model was established. First, two particles are used to simulate the interface constitutive behavior in different modes. The results show that the new model can better simulate the behavior of Mode-I fracture, Mode-II fracture, and Mixed-mode fracture. Then, the influence of micro-parameters on the newly constructed constitutive model is analyzed, which provides a basis for the determination of micro-parameter values. Finally, the proposed softening model is applied to a three-point bending test of mortar, and the fracture behavior obtained is compared to the acoustic emission results. The simulation results also show that the constitutive model we built can be used to simulate the fracture behavior of quasi-brittle materials such as mortar and concrete.

The removal of Pb(II) from aqueous solutions was investigated using kaolin with two different particle sizes (2.3 and 45 μm) with and without nanoscale zero-valent iron (nZVI, at a Fe content close to 30%). The experimental results show that 2.3 μm kaolin loaded with nZVI (K-nZVI) had the best Pb(II) removal performance under various test conditions. After 24 h, it removed 99.5% of Pb(II) ions in the solution, followed by 45 μm K-nZVI, 2.3 μm kaolin, and 45 μm kaolin (89.01%, 68.8%, and 65.8%, respectively). The removal rates by all four kaolin samples increased with increasing pH in the range of 2–6, and with increasing temperature between 30 °C–60 °C. The results show that using finer carrier particles improves the performance of K-nZVI for removing Pb(II) in aqueous solutions.

This paper describes a case of using a pile‐slab composite foundation to handle a bridge‐end bump problem. Conventionally, a deep‐seated concrete slab method is employed to tackle this problem; however, this method generates a large stress concentration within 1 m from the bridge end. The mechanical bearing capacity of the deep‐seated concrete slab is insufficient and prone to structural damage. Further, the longitudinal slope change rate is also very high. To overcome these limitations and solve the problem, a lower partition slab‐pile foundation treatment method is proposed. The construction of the proposed method is provided, and the results of a case study analyzed by field monitoring and a simulation executed using ABAQUS finite element simulation show good agreement. The results indicate that the mechanical bearing characteristics for the proposed lower partition slab‐pile foundation treatment method are better than the conventional deep‐seated concrete slab method, and therefore, the structure is more resistant to damage. In addition, because the pile foundation enhances the foundation bearing capacity, the longitudinal slope change rate of the new pile‐slab composite foundation is 2.5 times that for the deep‐seated concrete slab technology. Thus, the lower partition slab‐pile foundation treatment method can better deal with the bridge end bump problem.