Red mud replaced a part of cement to prepare red mud manufactured sand foam concretes to promote the utilization of red mud in the construction materials. The water-cement ratio, red mud dosage, sand-cement ratio and foam dosage was taken as single factor to study the corresponding effects on the physical properties, mechanical strength and water resistance of foam concretes. The hydration reaction mechanism and pore distribution characteristics were discussed by using X-ray diffraction, scanning electron microscopy and image processing techniques. The results showed that the foam concrete with 20 % red mud exhibited the optimal performance, the 28d compressive and flexural strengths were 13.68 MPa and 3.46 MPa, respectively, and the softening coefficient was 0.8. The volcanic ash effect and filling effect of red mud played a synergistic effect on the performance improvement of the foam concrete. The effect mechanisms of sand-cement ratio and foam dosage were owing to the physical change of the internal pore structures. The effect mechanisms of water-cement ratio and red mud dosage primarily were attributed to the changes of hydration reactions on the pore structures. The flocculent calcium silicate hydrate (C-S-H) gel and ettringite (AFt) were well wrapped around Ca(OH)2 crystals, and a homogeneous and complete pore structure was formed under the appropriate red mud dosage. Red mud decreased the cumulative proportion of small pores smaller than 200 mu m, and increased the cumulative proportion of medium and large pores larger than 200 mu m. The incorporation of red mud improved the mechanical strength, water resistance and pore distributions of foam concretes, verifying the feasibility of incorporating red mud into foam concretes.
