Effect of Different Activators on Properties of Slag-Gold Tailings-Red Mud Ternary Composite

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.