## 1 Introduction  
As an intelligent manufacturing technology developed in the past ten years, more and more groups worldwide are engaged in the research of 3D concrete printing. However, 3D concrete printing has the \"advantages of efficient printing speed, labor savings, and the ability to produce a wide range of shapes for printed products [1; 2; 3], the high cost of printing materials impedes the widespread adoption of 3D concrete printing [4]. Accordingly, there is immense importance in creating a printing material that is both low-cost and high-quality. Considering the environmental protection and the shortage of raw materials, replacing the main components of printing material with industrial waste can not just lower CO2 emissions [5] but also reduce the cost of printing material. However, to ensure printing performance, the admixture is indispensable. Therefore, replacing cement and natural aggregate with other industrial materials is one of the main research directions of 3D printing materials. In the aspect of cementitious material substitution, [PERSON] et al. [6] replaced cement with different dosages of fly ash (FA) as well as GBFS and studied the property changes of printing material with the change in cement replacement. It was observed that as the content of FA and GBFS increased, the initial increase in slump and expansion was followed by a decrease in slurry workability. [PERSON] al. [7] replaced cement with different kinds of brick powder and used sodium hydroxide, calcium hydroxide, and sodium silicate as alkaline activators to develop geopolymer printing material. The designed construction and demolition waste-based printing material was shown to be entitled to various printing performance requirements. In the aspect of aggregate replacement, steel slag and RCA, as common industrial wastes, have been used to produce 3D printing materials [8; 9; 10]. Compared with the expansion characteristic of steel slag, RCA was found to be more helpful to the improvement of the property of printing material. Over time, RCA's properties, such as its water absorption, would lead to an increase in the printing material's yield stress, which is advantageous for continuous printing [11]. However, to ensure the printability performance of the printing material, recycled construction aggregate would increase its water-cement (w/c) ratio because of the water absorption, which is negative to its mechanical performance. Although a superplasticizer could be used to reduce the w/c ratio, the utilization of a superplasticizer would increase the cost of the printing material. When the water-cement ratio is increased by 8%, the compressive strength will be reduced by about 12%, and if the high-efficiency water-reducing agent is used to reduce the water-cement ratio, the cost will be increased by about 15%. Therefore, it is of great value to produce a cheap admixture that could maintain the mechanical properties of printing materials under the condition of changing the w/c ratio. The chloralkali industry has quite extensive applications in China, usually using kosher salt to produce NaOH. As the main by-product of the chloralkali industry, the annual output of salt mud (SM) can reach about 2 Mt, and its main components are CaCO\({}_{3}\), Ma(OH)\({}_{2}\), and NaCl. While occupying a large amount of land, it also caused a certain degree of pollution to soil and water resources. At present, the main treatment methods of SM are landfills or dumping, and there is a lack of research focusing on its effective use. Because SM itself contains many inert components, it cannot be directly applied to building materials, but abundant CaO and MgO can be obtained through calcination, which makes it possible for SM to be used as an additive to ensure the stability of 3D printing materials, and there are few studies in this area, which can provide new insights for the utilization of SM and solid waste-based 3D printing.