## 2 Materials and Methods  
### Raw Materials  
A rapid hardening CEM I 52.5R type Portland cement (PC), a limestone filler (LF) and two types of calcined clay were used as the binder. The low-grade calcined clay (LCC) that contained 40-50% of MK and the high-grade calcined clay (HPCC) which contained near 90% of MK was produced by flash calcination of 95% kaolinite clay from Burgess (US). Different grades of calcined clay could be achieved by blending LCC and HPCC in different proportions. According to [PERSON] et al. [9], most of the 3 Dconcrete printers have limited nozzle sizes and up to 2 mm of sand was used in many studies [2; 8; 33]. Therefore, fine aggregate with a maximum diameter size of 2 mm was also selected in this study. Figure 1 shows the cumulative particle size distribution of all dry components. HPCC had the smallest average particle size amongst all of the dry components in this study. LCC contained a relatively higher content of coarse particles. The chemical composition of dry components was analyzed by X-ray fluorescence spectrometry (XRF) shown in Table 1. For figuring out the contents of the reactive SiO\({}_{2}\) and Al\({}_{2}\)O\({}_{3}\) in LCC and HPCC, a chemical dissolution method was utilized [34]. A proper amount of calcined clay was dissolved in dilute hydrochloric acid solution and afterward treated with boiling sodium carbonate solution [35]. The insoluble residue (I.R.) was rinsed, heated to around 950 \({}^{\circ}\)C, and cooled to the room's temperature (20 \({}^{\circ}\)C). Finally, the residue part was weighed by a scale and tested by XRF. The mass loss due to chemical dissolution can be regarded as the amorphous phase content. The amount of reactive SiO\({}_{2}\) and Al\({}_{2}\)O\({}_{3}\) is given in Table 2. The molar mass ratios of Si/Al in the reactive part of LCC and HPCC were 0.33 and 0.74 respectively. Besides, a Polycarboxylate Ether (PCE) based superplasticizer (MasterGlenium@51, BASF) was adopted in this research to achieve the required flowability, pumpability, and extrudability of mixtures. As described by [PERSON] et al. [36], superplasticizer could be used in the cementitious material to reduce yield stress and viscosity for enhancing the material workability at a constant solids volume. On the other hand, decreasing the water content at constant yield stress is also beneficial to reduce the porosity of the hardened cementitious material that contributes to improving the mechanical properties \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Oxide (wt. \%)** & **SiO\({}_{2}\)** & **Al\({}_{2}\)O\({}_{3}\)** & **CaO** & **Fe\({}_{2}\)O\({}_{3}\)** & **K\({}_{2}\)O** & **TiO\({}_{2}\)** & **ZrO\({}_{2}\)** & **Other** & **Total** \\ \hline PC & 17.4 & 4.1 & 68.7 & 2.8 & 0.6 & 0.3 & 0 & 6.1 & 100.0 \\ LF & 0.2 & 0 & 39.6 & 0.1 & 0 & 0 & 0 & 60.1 & 100.0 \\ LCC & 55.1 & 38.4 & 0.6 & 2.6 & 0.2 & 1.1 & 0.1 & 1.9 & 100.0 \\ HPCC & 47.3 & 50.6 & 0 & 0.5 & 0.2 & 1.3 & 0 & 0.1 & 100.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The chemical composition of the main components in the binder (wt. %). Figure 1: Particle size distribution of dry components. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Components** & **I.R.** & **Reactive** & **Reactive** & **Reactive** & **Other Reactive** \\
**(wt. \%)** & **Content** & **SiO\({}_{2}\)** & **Al\({}_{2}\)O\({}_{3}\)** & **Phases** \\ \hline LCC & 51.2 & 48.8 & 12.3 & 32.0 & 4.5 \\ HPCC & 24.9 & 75.1 & 34.6 & 39.9 & 0.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Reactivity of low-grade calcined clay (LCC) and high-grade calcined clay (HPCC) (wt. %). and durability. Currently, PCE is reported as the most effective superplasticizer for commercial use [35; 36]. While superplasticizer is only used for adjusting printing properties such as pumpability and extrudability, it still requires other admixtures to retain the shape of the deposited material upon extrusion. Based on the research of [PERSON] et al. [37], [PERSON] and [PERSON] [38] and [PERSON] et al.