Red mud (RM) and Yellow River sediment (YRS) are challenging to handle as waste materials. In this study, RM with geopolymer and heavy metal adsorption characteristics was combined with YRS and ground granulated blast furnace slag (GGBS) to develop a porous geopolymer with high strength and high adsorption performance. A geopolymer cementitious material with high strength was prepared using high temperature water bath curing of 90 °C and different dosages of YRS, and a porous geopolymer concrete was further prepared. The compressive strength, fluidity and setting time of geopolymer cementitious materials were tested, and the compressive strength, porosity and permeability of porous geopolymer concrete were also tested. The environmental impact assessment of geopolymer cementitious materials was further conducted. The hydration products and microstructure of geopolymer gel materials were analyzed by XRD, SEM and FT-IR tests. The results show that the addition of YRS can effectively prolong the setting time of the geopolymer cementitious material, and the enhancement rate is as high as 150% compared with the geopolymer cementitious materials without the addition of YRS. An appropriate amount of YRS can improve the compressive strength of the geopolymer cementitious materials, and its early compressive strength can be further improved under the high temperature water bath curing of 90 °C, and the compressive strength at an age of 3 d can be up to 86.7 MPa. Meanwhile, the compressive strength of porous geopolymer concrete at an age of 28 d is up to 28.1 MPa. YRS can participate in geopolymer reactions, and high temperature water bath curing can promote the reaction degree. Curing method and YRS dosages have little effect on the porosity and permeability of the porous geopolymer concrete. The porous geopolymer has a good heavy metal adsorption effect, and the alkaline pH values can be gradually diluted to neutral.

To enhance the application value of sand washing residue mud (SWRM) and mitigate its adverse environmental impacts, this study focuses on the resource utilization of SWRM. The research employed a combined mechanical–thermal activation method to enhance the activity of SWRM and utilized the mixed optimal design module to design and optimize the mixing ratio of SWRM-based LC3 cement. The results showed that within a ball-milling time range of 3–9 min, as the ball-milling time increased, the specific surface area increased, the median particle size D₅₀ decreased, and the particle size was mainly concentrated within the range of 0.1–30 μm; the specific surface area of the washed sand residue after 3 min of grinding reached 1080 m²/kg, with D₅₀ being 3.50 μm, which met the requirements for making cementitious materials. After thermal activation at temperatures ranging from 450 °C to 950 °C for the 3 min ground SWRM, the 28 d activity index showed a trend of increasing first and then decreasing with the increase in calcination temperature, and the 28 d activity index reached the maximum of 79.3% at a calcination temperature of 650 °C. The optimal mixing ratio of the AC70 group’s SWRM-based LC3 cement obtained through the mixing design was: cement clinker 66.5%, desulfurized gypsum 3.5%, activated SWRM 15%, and limestone powder (LP) 15%. The 28 d compressive strength of the AC70 group’s SWRM-based LC3 cement was 34.1 MPa, with initial setting and final setting times of 170 min and 240 min respectively, and the volume stability was qualified. The microscopic test results indicated that under the synergistic effect of alkali and salt, the silicate and aluminosilicate tetrahedral structures in the active sand-washed mud (ASWRM) decomposed, forming a C-(A)-S-H network structure, which was the main source of strength for the SWRM-based LC3 cement in the later stage. The ecological benefit calculation and analysis showed that compared with ordinary Portland cement of the same grade, the AC70 group’s SWRM-based LC3 cement had a 27.6% reduction in implicit energy consumption, a 44.1% reduction in carbon emissions, and a 25% reduction in cost. This study provides an innovative approach for the high value-added resource utilization of SWRM.