## 1 Introduction  
Numerous studies [1; 2; 3; 4] have been conducted to improve the mechanical properties of cementitious composites concerning both strength and ductility. One of the effective ways for enhancing tensile ductility is to incorporate reinforcing fibers into cementitious composites. Thus, various methods of reinforcing cementitious composites with steel or polymeric fibers have been developed and improved upon by researchers. Slurry infiltrated concrete (SIFCON), engineered cementitious composite (ECC), reactive powder concrete (RPC), and ultra-high-performance concrete (UHPC) are a few strain-hardening cementitious composites (SHCCs) that have been investigated in the past [1; 2; 3; 4]. Among the diverse materials, ECC and UHPC are the two most representative SHCCs that continue to be improved upon and applied in structural elements. UHPC containing 2 vol.% steel fibers typically has compressive strength, tensile strength, and strain capacity of around 150 MPa, 8 MPa, and 0.5%, respectively. Particle packing theory of the reactive and non-reactive mineral additives was designed to improve performance significantly [5; 6]. Thus, the UHPC generally consists of ordinary Portland cement (OPC), silica fume (SF), silica sand, and silica flour, to develop a more compact and homogeneous microstructure. Engineered cementitious composite (ECC) is Pa different type of cementitious composite that exhibits high ductility by incorporating 2 vol.% of polymeric fibers. Unlike steel fibers, polymeric fibers, with a low surface hardness, damage the fiber-matrix interface less when the fibers are pulled out. Therefore, the cementitious matrix can persistently resist to pullout of the polymeric fibers and obtain a higher strain capacity of 5% or more [2,7,8]. The tensile strength of ECC, however, is generally lower than that of the UHPC ranging between 5-8 MPa. Thus, many researchers have been working toward improving the mechanical performance of cementitious composites further to obtain enhanced strength and high ductility. In general, ground granulated blast furnace slag (GGBS), silica fume (SF), silica flour have been considered in designing fiber-reinforced cement composites (FRCCs) to improve the physical properties. The GGBS is also well known as a mineral additive that goes through the second hydration process after the dissolution of its glassy shell. This was the reason why researchers used the alkaline substances to activate GGBS-based polyethylene (PE) fiber-reinforced composites [7,8]. Thus, the rate of the development of microstructure and mechanical performance is slower than that of the OPC, which directly reacts with water. The SF is also a representative pozzolanic mineral additive, which has frequently been used in FRCCs. Due to its very fine particular size, it has many benefits from the points of reactivity, particle packing and compressive strength, and flowability of the fresh FRCC mixes [9, 10, 11, 12]. Cement kiln dust (CKD) can also be effectively used in cementitious composites as binders when its alkali and sulfur concentrations can be reduced. By controlling the alkali and sulfur concentrations, the CKD becomes highly reactive and promotes the development of early strength or activation of the GGBS [13,14]. Although a number of studies have investigated the influence of the reactive and non-reactive supplementary materials, only a few studies were relevant to ultra-high-performance, strain-hardening cementitious composites (UHP-SHCCs). Recently, researchers have reported ultra-high-performance, strain-hardening composite materials reinforced with polyethylene (PE) fibers [7,8,15]. Alkali-activated GGBS-based composites showed tensile strengths ranging between 8-17.4 MPa and strain capacities between 7-8% [7,8]. [PERSON] et al. [7] and [PERSON] et al. [8] tried to eliminate the OPC from the composites and fix the binder types by using 90% or 100% of GGBS. In [7,8], they focused on examining the influence of types of alkaline substances and water to binder ratios on mechanical performance.