As landfill space for the disposal of products of municipal solid waste incineration (MSWI) such as fly ash and slag becomes increasingly scarce, a reduction of disposed material is urgently required. The method of using incineration products in concrete production is explored in this paper through a feasibility study of utilizing fly ash and slag to replace cement and coarse aggregate in appropriate proportions. Results show that C30 concrete optimum replacement rates of fly ash and slag are 30% and 20%, which can meet the minimum strength requirement. The leaching concentrations of Cu, Zn, Pb, Cr, and Cd in MSWI concrete samples are determined to be less than the identification value of solid waste leaching toxicity. Based on scanning electron microscopy (SEM) and X‐ray diffraction (XRD) analyses, MSWI fly ash has certain dispersion. The particle size of MSWI fly ash is determined to be close to that of the coal fly ash, and the surface morphology is irregular. The main components include SiO₂, CaCO₃, and Ca₂SiO₄, and they are similar to those present in the coal fly ash. The slag structure is loose as well as irregular, and its main component is SiO₂. The SiO₂ and Al₂O₃ in fly ash and slag participate in the hydration reaction of cement and can increase concrete strength. It is thus confirmed that fly ash and slag generated by waste incineration can be used to replace cement and coarse aggregate in appropriate proportions, and it is an effective method to solve the problem of scarcity of solid waste landfill space.

This work aims to investigate the seismic behavior and shear bearing capacity of Ultra-High Performance, Fiber-Reinforced Concrete (UHPFRC) beam-column joints. Quasi-static tests were conducted on five exterior and four interior reinforced UHPFRC beam-column joints; the behavior of specimens was examined in terms of failure processes, shear deformation angle, load transfer, and loadbearing capacity. The influences of the joint types, axial compression load level, and stirrup ratio in joint cores on the failure modes and shear carrying capacity of joints were analyzed. The shear resistance mechanism of a reinforced UHPFRC beam-column joint consists of the diagonal strut and truss mechanisms. The role of steel fiber through cracks is similar to reinforcement bars in the truss mechanism; based on these mechanisms and the test results, a formula was proposed to predict the shear carrying capacity of reinforced UHPFRC joints. The formula can reflect the effects of axial compression load level, steel fiber content, and stirrup ratio in the joint core on the shear carrying capacity of the beam-column joint, which can be used not only for UHPFRC beam-column joint design, but also steel fiber high-strength concrete joints.

To investigate the influence of the fly ash (FA) content on the performance of high-performance concrete (HPC), seven groups of tests were conducted, aiming to evaluate both the macroscopic properties (workability and compressive strength) and microscopic pore structure. Low-field nuclear magnetic resonance (NMR) technology and SEM images were employed to analyze the changes in the internal pore structure of the concrete. The results showed that the workability of HPC initially increased and then decreased with the increase in the FA content. When the FA content was 15%, the slump of HPC reached a maximum of 264 mm, and the 28-day compressive strength exhibited a 23.2% increase compared to the 7-day compressive strength. The pore size distribution of the concrete varied with different fly ash content. At 15% FA content, secondary hydration of the FA was sufficient, refining the pores to between 0 and 0.1 µm. Excessive FA substitution deteriorated the internal structure of the HPC matrix and reduced the workability and mechanical properties of the HPC. When the content of FA was 35%, the slump of HPC decreased to 176 mm, while the macropores within the matrix significantly increased, resulting in porosity of 6.81%.