Mix proportion optimization of red mud manufactured sand foam concrete and its sulfate resistance

This study optimized the mix proportion of red mud manufactured sand foam concrete (RMMSFC) using orthogonal tests and evaluated its sulfate resistance. Results showed that the sand-cement ratio most significantly influenced dry density and porosity, while foam content predominantly governed strength. Through range analysis, variance analysis, and comprehensive scoring, the optimal mix was determined as water-cement ratio 0.27, red mud content 30%, sand-cement ratio 0.9, and foam content 8%, achieving a 28-day compressive strength of 18.79 MPa and dry density of 1724.50 kg/m³. Microstructural analysis indicated that active components in red mud participated in secondary hydration, producing C-S-H gel and ettringite, thereby refining pore structure. Sulfate resistance tests revealed that specimens with ≤ 30% red mud retained good integrity after 50 wet-dry cycles. When the content of red mud is over 30%, the comprehensive performance decreases significantly due to the accelerated decomposition of hydration products and the expansion and accumulation of erosion products in the high alkali environment.