## 2 Materials and Experimental Methods
### Test Methods  
To assess the effects of FCC residue contents on rheological and hardened properties of geopolymer concrete, such as yield stress, plastic viscosity, elastic modulus, and compressive and flexural strength, testing methods in compliance with ASTM standards were carried out. Rheological properties were calculated based on the slump value obtained from the modified slump cone test [31], which is illustrated in Figures 2 and 3. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Mix ID**} & \multicolumn{3}{c}{**Mix Design Parameters**} & \multicolumn{3}{c}{**Mass of Constituent Materials (kg)**} \\ \cline{2-9}  & **AL:GS** & **FCC Residue (\%)** & **CA** & **FA** & **Fly Ash** & **FCC Residue** & **Sodium Silicate** & **Sodium Hydroxide** \\ \hline G1 & 0.65 & 0 & 1098 & 810 & 300 & 0 & 97.5 & 97.5 \\ G2 & 0.65 & 20 & 1098 & 810 & 240 & 60 & 97.5 & 97.5 \\ G3 & 0.65 & 40 & 1098 & 810 & 180 & 120 & 97.5 & 97.5 \\ G4 & 0.65 & 60 & 1098 & 810 & 120 & 180 & 97.5 & 97.5 \\ G5 & 0.65 & 80 & 1098 & 810 & 60 & 240 & 97.5 & 97.5 \\ G6 & 0.65 & 100 & 1098 & 810 & 0 & 300 & 97.5 & 97.5 \\ G7 & 0.5 & 0 & 1063 & 770 & 400 & 0 & 100 & 100 \\ G8 & 0.5 & 20 & 1063 & 770 & 320 & 80 & 100 & 100 \\ G9 & 0.5 & 40 & 1063 & 770 & 240 & 160 & 100 & 100 \\ G10 & 0.5 & 60 & 1063 & 770 & 160 & 240 & 100 & 100 \\ G11 & 0.5 & 80 & 1063 & 770 & 80 & 320 & 100 & 100 \\ G12 & 0.5 & 100 & 1063 & 770 & 0 & 400 & 100 & 100 \\ G13 & 0.4 & 0 & 950 & 760 & 500 & 0 & 100 & 100 \\ G14 & 0.4 & 20 & 950 & 760 & 400 & 100 & 100 & 100 \\ G15 & 0.4 & 40 & 950 & 760 & 300 & 200 & 100 & 100 \\ G16 & 0.4 & 60 & 950 & 760 & 200 & 300 & 100 & 100 \\ G17 & 0.4 & 80 & 950 & 760 & 100 & 400 & 100 & 100 \\ G18 & 0.4 & 100 & 950 & 760 & 0 & 500 & 100 & 100 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Mix design of geopolymer concrete. Yield stress could be identified from the final slump, using the following equations [32]:  
\[\tau_{0}=\frac{\rho}{347}(300-S)+212 \tag{1}\]  
where \(\tau_{0}\) is yield stress (Pa); \(\rho\) is geopolymer concrete density (kg/m\({}^{3}\)); and \(S\) is geopolymer concrete slump (mm). The viscosity was determined from the 100 mm slump time using an empirical formulation [31], which is:  
\[\mu=\rho T\times 1.08\times 10^{-3}(S-175)\text{ for }200\text{ mm }<S\text{ }<260\text{ mm} \tag{2}\]  
\[\mu=0.0025\text{pT for }S\text{ }<200\text{ mm} \tag{3}\]  
where \(\mu\) is plastic viscosity for geopolymer concrete (Pa-s) and \(T\) is partial slump time (s). In this study, Equation (3) was used to calculate the plastic viscosity of geopolymer concrete because all values of slump are lower than 200 mm. Elastic modulus was assessed after 7 days in accordance with ASTM C469 [33] by measuring stress and longitudinal strain of cylindrical geopolymer specimens (150 mm diameter \(\times\) 300 mm height). Specimens were subjected to compressive load at a constant rate of 0.24 \(\pm\) 0.03 MPa/s and secant modulus values recorded at a stress level of 40% of the corresponding average compressive cylinder strength. Compressive strength testing was performed on cylindrical specimens (100 mm diameter \(\times\) 200 mm height) with loading rates ranging from 0.15 to 0.35 MPa/s in accordance with ASTM C39 [34]. Flexural strength testing was carried out on simply supported 100 \(\times\) 100 \(\times\) 400 mm beams with a span length of 300 mm in accordance with ASTM C78 [35]. Loading rates ranged from 0.86 to 1.21 MPa/min to the point of failure. For all strength tests, a group of four specimens was fabricated for one mix proportion. In total, 216 specimens were used for strength tests in this research. In addition to physical and mechanical testing, scanning electron microscopy (SEM) VEGA 3 SBH (TESCAN) was used for morphological study. The samples used for the SEM test were picked up from broken pieces of specimens after testing. The X-ray diffractometer DE/D8 Advance, Bruker mark using CuK\(\alpha\) radiation was used to perform XRD analyses. Figure 3: Device used for modified slump cone test [31].