Red mud is a kind of solid waste produced in the process of aluminum extraction. Traditional methods of red mud treatment, such as open-pit accumulation and chemical recovery, are costly and environmentally hazardous. Gold tailings are industrial by-products produced in the process of gold mining and refining. In this study, NaOH, KOH, and Na₂SiO₃ were used as activators, and their effects on the properties of ternary cementitious composite containing blast furnace’s slag, gold tailings, and red mud were studied with the intention of preparing a new cementitious material that is an efficient recovery and utilization of solid waste. The macroscopic mechanical properties and hydration of the ternary cementation material were studied by means of compressive strength, XRD, FT-IR, and TG/DTG. The compressive strength testing showed that the maximum strength at 28 d was 43.5 MPa. The hydration products in the ternary cementitious system were studied by SEM and EDS, and it has been demonstrated that the strength of this cement was due to the formation of Aft (AFt, also known as Ettringite, has the chemical formula 3CaO·Al₂O₃·3CaSO₄·32H₂O. It is one of the important hydration products of cement-based cementitious materials, which can not only provide early strength for cement, but also compensate for early shrinkage of concrete.) and C-A-S-H gels. Samples activated by Na₂SiO₃ presented a most compact microstructure and the best macroscopic mechanical properties than the samples free of activator. The toxicity tests results showed that the content of heavy metal ions liberated by the cement’s leaching met the standard requirements, proving that the slag-gold tailings-red mud ternary composite was environmentally friendly.

This study analyzes the mechanical properties of high ductility concrete (HDC) under different ambient temperatures to provide a parameter basis for the design of HDC bridge deck link slabs. Five temperatures (−30, 0, 20, 40, and 60 °C) were designed to investigate the compressive, tensile, and flexural properties of HDC after temperature treatment and analyze the pore structure. The results show that, compared with the HDC performance at room temperature (20 °C), the compressive strength, ultimate tensile strength, and flexural strength decreased after treatment at low temperatures (−30 and 0 °C), while the strength increased after treatment at high temperatures (40 and 60 °C). After experiencing low- and high-temperature treatments, the ultimate tensile strain and ultimate deflection of the HDC increased. The tensile and flexural failures of the HDC exhibited multiple cracking, and the stress–strain/deflection curve showed a strain/deflection hardening stage. The tensile constitutive relationship can be simplified as a bilinear two-stage relationship. As the temperature increased, the porosity of harmless and less harmful pores in HDC gradually increased, while the porosity of harmful and more harmful pores gradually decreased, resulting in an increase in HDC strength. Based on the influence of temperature on HDC properties, design parameters for the HDC bridge deck link slab structure are proposed.

Three gradations of fine iron tailings are selected to prepared surface mortar for external thermal insulation on outer-walls for replacing natural sand. The working performance and mechanical performance of the surface mortar for external thermal insulation on outer-walls are studied. The results show that the water requirements of surface mortar for external thermal insulation on outer-walls is almost no difference at same consistency when the dosage of 0-0.1mm, 0.1-0.3mm and 0.3-0.5mm fine iron tailings is respectively below 80g/kg, 100g/kg, 150g/kg, and the flexural strength, compressive strength and tensile adhesive strength at 28d of surface mortar for external thermal insulation on outer-walls is higher than it prepared natural sand. The water requirements of surface mortar for external thermal insulation on outer-walls prepared by fine iron tailings instead of all natural sand is 24% higher than it by prepared natural sand, the flexural strength, compressive strength and tensile adhesive strength at 28d of surface mortar for external thermal insulation on outer-walls is slightly lower than it prepared by natural sand. The working performance and mechanical performance of the surface mortar for external thermal insulation on outer-walls by fine iron tailings instead of all natural sand can meet requirements of JC/T 2084-2011.