## 1 Introduction  
Bayer red mud is the residue of alumina produced by the Bayer process, after the dissolution of bauxite with caustic soda, which is characterized by a high water content, a small particle size, and a high alkali content with an average pH value of 11.3 \(\pm\) 1.0 [1,2]. This is also a toxic industrial waste, with a global stockpile of over 2.7 billion tons, causing great harm to the environment [3]. With the intensification of environmental and lack of resources problems, the environmentally sound and comprehensive utilization of red mud has become an important research topic with regard to sustainability. Using Bayer red mud, ground granulated blast furnace slag and a certain ratio of alkali activator to prepare a new clinker-free water-hardenable cementitious material, namely, alkali- activated slag-red mud (AASR) is a promising approach which can offer high strength development, high resistance against chloride ingress, high resistance against chemical attacks, and superior durability [4,5]. The development of AASR and its related technologies cannot only make full use of the residual value of red mud to reduce the consumption of natural resources, but can also solve the environmental problems caused by red mud stockpiling. In addition, the use of AASR to replace ordinary silicate cement (OPC) can reduce CO\({}_{2}\) emissions by more than 75% and energy consumption by 60% [6]. Therefore, AASR has a rather broad application prospect, and is thus favored by scholars at home and abroad. The basic mechanical properties are a vital fundamental parameter and an important prerequisite for the application of AASR, so as to judge, understand and optimise the performance of AASR; however, the research on the mechanical properties of AASR is still in its initial stages. It is also important to mention that there are differences in the research results of scholars from different institutions and regions [4; 7; 8]. [PERSON] et al. prepared alkali-activated slag-red mud material with a 30% red mud admixture using Na\({}_{2}\)SiO\({}_{3}\) of 6.9% alkali equivalent (modulus 1.7) after drying and activating the red mud at 100 \({}^{\circ}\)C, having found that the compressive strength at 24 h of curing was 18.53 Mpa [9]. [PERSON] et al. finely ground the dried red mud and used Na\({}_{2}\)SiO\({}_{3}\) at 30% concentration (modulus 2.0) to prepare alkali-activated slag-red mud material with 50% red mud admixture, having found a compressive strength of 86 MPa after 28 days [10]. [PERSON] et al. activated red mud at high temperature, and prepared an AASR with a 60% red mud admixture using Na\({}_{2}\)SiO\({}_{3}\)-3.2H\({}_{2}\)O (modulus 2.4), having found a compressive strength of 76 MPa after 48 h of curing [11]. [PERSON] et al. found that 50% of red mud and 50% of slag obtained the highest strength, with an alkali exciter of modulus 1.5, and that calcium vanadinite and C-S-H gels were responsible for the development of the strength of alkali excited slag red mud cementitious material [12]. [PERSON] pointed out that when the calcination temperature of red mud is 700 \({}^{\circ}\)C, the Si-O bonds and Al-O bonds break, thus showing good mechanical properties [13]. [PERSON] et al. prepared and found feasible belite-rich sulphoaluminate cement repair material based on synergistic theory using red mud, slag and desulfurization gypsum [14]. [PERSON] verified the appropriate amounts of RM that enabled the promoting of the alkali-activated reaction of slag [15]. Clearly, the mechanical properties of AASR are affected by several factors, such as the dosage of red mud, the type and dosage of the alkali activator, the modulus of the water glass, the maintenance method of red mud, and the treatment method of red mud, etc., among which the dosage of red mud is one of the most basic influencing factors.