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.

In order to reduce the negative impact on the environment caused by the massive accumulation of red mud (RM) and Yellow River sand (YRS), new alkali-excited granulated blast-furnace slag (GGBS)/RM/YRS (AGRY) geopolymer cementitious materials were prepared by combining RM and YRS with GGBS in different ratios and using sodium silicate as the alkali exciter. The effects of YRS dosage and different curing conditions on the mechanical properties, hydration products, and pore structure of cementitious materials were investigated and analyzed in terms of cost and carbon emissions. The results showed that when the dosage of YRS was 40%, the compressive strength of the prepared AGRY cementitious material could reach 48.8 MPa at 28 d under standard curing, which showed mechanical properties comparable to those of the cementitious material without YRS. The cementitious material has a more compact internal structure, and the combination of RM and YRS promotes the chemical reaction of Al and Si elements and generates the (N, C)-A-S-H gel products, which are the key to the strength enhancement of the cementitious material. In addition, the prepared cementitious material is only 90% of the cement cost for the same strength and has low carbon emission accounting for only 43% of the cement carbon emission. This study not only provides a new way for the resource utilization of RM and YRS, but also contributes an excellent new environmentally friendly material for the construction industry to achieve the goal of low carbon development.