# Hydration of Calcium Sulfoaluminate-Based Binder Incorporating Red Mud and Silica Fume  
[PERSON]  
1 Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea; [EMAIL_ADDRESS] (Y.J.); [EMAIL_ADDRESS] (J.H.K.)  
[PERSON]  
1 Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea; [EMAIL_ADDRESS] (Y.J.); [EMAIL_ADDRESS] (J.H.K.)  
[PERSON]  
2 Department of Civil Engineering, Pusan National University, Busan 46241, Korea  
disposal of RM is therefore a significant environmental issue, and the re-utilization of RM should receive more attention.  
Several studies have explored the possible reuse of RM in the production of cementitious or pozzolanic material-based binders [14; 15; 16]. [PERSON] et al. [15] have studied the mechanical properties of composed samples with RM, coal refuse, fly ash, cement, and gypsum. They reported that the combined sample met the requirement of ASTM standards in physical and mechanical tests, and concluded that the sample could be used as ordinary Portland cement (OPC) substitute material. [PERSON] et al. [16] reported the pozzolanic properties of dry and calcined RM, and showed that OPC replaced by RM contained the hydration products of C-S-H, ettrinigite, monosulfate, and C-A-H. They described how SiO\({}_{2}\), Al\({}_{2}\)O\({}_{3}\), and Fe\({}_{2}\)O\({}_{3}\) contained in RM contribute to the pozzolanic activity. Some studies have used RM as an alkali activator for the synthesis of geopolymers or alkali-activated slag because RM generally has high alkalinity [17; 18]. [PERSON] et al. [17] proposed that RM could provide solid alkali activation for making a fly ash-based geopolymer.  
[PERSON] et al. [19] used RM for the manufacture of lightweight aggregate as a replacement for pulverized fuel ash. They showed that the manufactured lightweight aggregate had good physical characterizations: compressive strength, density, and water holding capacity. It was expected that the produced lightweight aggregate made with RM could be used in concrete and other construction products [19; 20]. [PERSON] and [PERSON] [20] reported that RM used with cement, fly ash, and sand would be effective in reducing autogenous shrinkage of self-compacting mortar.  
Silica fume (denoted as SF) is a pozzolanic material that is a by-product in the manufacture of silicon metal. Due to its high surface area and microparticles, SF is used to enhance the strength and durability of concrete [21; 22]. It contributes to the permeability reduction of concrete as a pore filler.  
As mentioned above, several studies have reported on the characteristics of CSA, RM, and SF, which are a low-carbon material and an industrial by-product. From the viewpoint of resources recycling and environmental pollution, further studies will be needed to use by-products in a variety of ways. The objective of this study is to develop eco-friendly ternary blended binders made of CSA, RM, and SF. In this study, compressive strength and drying shrinkage as well as the results of X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) with energy dispersive spectroscopy (EDS), and mercury intrusion porosimetry (MIP) of hardened samples with CSA, RM, and SF were analyzed.