## 1 Introduction  
Portland cement (PC) has become a widely used bonding material because of its excellent strength and durability, as well as its economic advantages. However, with the growing greenhouse effect, people are looking for alternative adhesive materials to PC due to the large amount of CO\({}_{2}\) emitted during the production of PC [1]. Alkali-activated material (AAM) is an adhesive that has been developed to replace PC, and the aim was to develop an environmentally friendly adhesive [2]. Some studies have shown that the use of AAM can reduce CO\({}_{2}\) emissions by 40-80% compared to PC [3]. AAM is manufactured by activating a solid silica-aluminate precursor material with an alkali activator [4]. Silica-aluminate-rich materials generally include metakaolin, silica fume, fly ash, steel slag, red mud and blast furnace slag [5, 6]. Considering the current high emissions and low utilization of red mud and steel slag, their large stockpiles bring a series of environmental problems [7, 8], and it is necessary to develop eco-friendly technologies regarding waste (e.g., steel slag and red mud) resources [9]. In this paper, we use blast furnace slag, red mud, steel slag and an alkali activator to produce a clinker-free binder called alkali-activated slag-red mud-steel slag cementitious material (AASRSS). It is a promising binder because the development of AASRSS can not only relieve the economic and environmental pressure caused by steel slag and red mud [10], but it can also replace part of the cement and reduce the production of cement, and, thus, reduce CO2 emissions [11], which is in line with the national strategy of \"sustainable development\" in China. As a potential substitute for cement, AASRSS has good mechanical properties and an excellent resistance to chemical attack [12]. Despite its favorable performance, the widely recognized applications of AASRSS in the industry have been hindered, partly due to concerns related to its long-term durability, such as extensive shrinkage and micro-cracking, rapid carbonation, and potential alkali-aggregate reactions. One of the most significant conundrums impeding the implementation of AASRSS is its higher water sorptivity, caused by the high content of alkali-containing salt in red mud and the poor volumetric stability [13]. This means that AASRSS is more susceptible to durability issues due to the fact that water transport in porous matrices is a source of multiple factors for material deterioration or loss of function [14,15]; for example, a high water sorptivity can lead to the easy penetration of water carrying corrosive ions into the interior of the material, which can destroy the microstructure of the material, leading to a reduction in the compressive strength of the material. Therefore, reducing water absorption is an important issue to be addressed before the promotion and application of AASRSS. Hydrophobic treatment is one of the measures commonly employed for cementitious materials [16]. This faces a practical difficulty, however, in that some water repellents developed for OPC lose their functionality in alkali-activated systems, such as sodium methylsilicate, a common OPC water repellant; the highly alkaline environment of an alkali-activated system causes the water-repellent film formed by sodium methylsilicate to hydrolyze and lose its water repellency [17]. Recently, stearates have gained wide attention as waterproofing materials due to their low cost and effectiveness [18, 19, 20]. Some studies have shown that the incorporation of stearates can effectively reduce the water absorption rate of alkali slag cement stones [21]; however, there are very limited studies related to the application of stearates in alkali-excited multivariate composite systems. In addition, to the authors' knowledge, a study on the application of sodium stearate (C17H35 COONa, NaSt) to the AASRSS system has not been reported.