Preparation of non-sintered building materials with a high content of red mud using magnesium oxychloride cement

[Display omitted] •The inclusion of red mud enhances the mechanical properties of MOC.•An optimal additive is crucial for the strength development of MOC.•Red mud enhances the density of MOC, resulting in improved compactness.•Whether or not a modifier is added, it does not efflorescence.•Greater environmental friendliness and cost-effectiveness advantages was achieved. With the increasing concern of environmental problems, the effective utilization of red mud is becoming more and more challenging. In this study, research on the combination of red mud and magnesium oxychloride cement was systematically carried out to prepare a non-sintered building material with a high content of red mud. Molar ratio of MgO/MgCl2, content of red mud and aggregate, modifiers exhibited significant impact on mechanical properties and water resistance of the building materials. The results demonstrated that the flexural strength, compressive strength, and softening coefficient of the test blocks reached 7.37 MPa, 35.7 MPa, and 0.91, respectively when the optimal condition was applied. Mechanism analysis showed that red mud particles interacted with the hydration products of MOC to form an amorphous gel, improving the degree of matrix compactness and effectively blocking the infiltration of external water, thus enhancing the mechanical strength and water resistance of the building materials. Finally, the cost analysis revealed that the construction materials developed in this study were significantly lower than the prices of those available on the market. These findings offer invaluable guidance for the utilization of red mud as building materials.