Red Mud in Combination with Construction Waste Red Bricks for the Preparation of Low-Carbon Binder Materials: Design and Material Characterization

The effective and safe treatment of red mud has become a pressing global issue in recent years. The purpose of this study is to prepare different systems of low-carbon cementitious materials by combining various solid wastes (slag powder, red brick of construction waste) with different systems of low-carbon cementitious materials and to observe the effects of different cementitious compositions on the construction performance, mechanical properties, freeze–thaw resistance, and heavy metal leaching properties by designing different systems of low-carbon cementitious materials, as well as to analyze the microscopic morphology, mineral composition, and strength-forming mechanisms of the different systems of low-carbon cementitious materials through the use of X-ray fluorescence (XRF), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) techniques. The findings reveal that a ternary cementitious system containing 16% red brick powder exhibits the most favorable overall performance. Compared to a binary system, this mixture improves fluidity by 4.5%, increases compressive strength by 18.27%, reduces drying shrinkage by 39.56%, and lowers the mass loss rate during dry–wet cycling by 11.07%. Furthermore, the leaching levels of heavy metals such as Cr, As, Pb, Ni, and Cu in the red mud-based cementitious materials, combined with multiple solid wastes, are within the safe limits for non-hazardous environmental release, as specified by Chinese regulations, under both freeze–thaw and non-freeze–thaw conditions. This study demonstrates for the first time the potential of combining red mud with construction waste brick dust and provides a scientific basis and theoretical guidance for the synergistic utilization of alkaline solid waste, calcium solid waste, and silica–aluminum solid waste.

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