# Characterization of Slag Cement Mortar Containing Nonthermally Treated Dried Red Mud
## 3 Characterization of Slag Cement Mortar Containing RM and NTRM
### Experimental Results and Discussion
#### 3.4.2 Porosity  
Figure 8 shows the pore size characteristics of SC100, SC80 RM20, and SC80 NTRM20. As pore characteristics, the total porosity and pore size distribution were measured. The total porosities of SC100, SC80 RM20, and SC80 NTRM20 were 17.16%, 20.78%, and 22.66%, respectively. The total porosities of SC80 RM20 and SC80 NTRM20, which included RM, were 3%-5% higher than that of SC100. Among the samples, SC80 NTRM20 had the highest total porosity.  
In the pore size distribution, it was found that there were relatively more pores with the three sizes of 10-100, 1000, and 100,000 nm. In general, pores with 0-1000 nm sizes represent capillary voids, and pores with 100,000 nm sizes represent air bubbles [31]. Pores with 10-100 nm sizes, which correspond to small capillary pores, were found to have the largest distribution in SC80 RM20 and the smallest distribution in SC100. Pores with 1000 nm sizes, which correspond to relatively large capillary voids, were found to have the largest distribution in SC80 NTRM20 and the smallest  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Specimen ID**} & \multirow{2}{*}{**Age (d)**} & \multicolumn{5}{c}{**Compressive Strength (MPa)**} \\ \cline{3-6}  & & **no.1** & **no.2** & **no.3** & **Average** & **CV 1** \\ \hline \multirow{4}{*}{SC100} & 1 & 6.24 & 6.34 & 6.19 & 6.26 & 0.07 \\  & 3 & 13.36 & 13.99 & 14.49 & 13.95 & 0.56 \\  & 7 & 23.55 & 18.63 & 21.96 & 21.38 & 2.50 \\  & 28 & 30.08 & 30.53 & 29.81 & 30.14 & 0.35 \\ \hline \multirow{4}{*}{SC80 RM20} & 1 & 5.18 & 4.87 & 5.01 & 5.02 & 0.15 \\  & 3 & 11.81 & 11.83 & 11.87 & 11.84 & 0.03 \\  & 7 & 20.18 & 17.62 & 18.71 & 18.83 & 1.28 \\  & 28 & 24.74 & 27.67 & 25.33 & 25.91 & 1.55 \\ \hline \multirow{4}{*}{SC80 NTRM20} & 1 & 4.19 & 3.82 & 3.84 & 3.95 & 0.21 \\  & 3 & 9.31 & 10.28 & 10.26 & 9.95 & 0.55 \\ \cline{1-1}  & 7 & 15.92 & 13.24 & 15.70 & 14.95 & 1.49 \\ \cline{1-1}  & 28 & 20.84 & 18.78 & 20.33 & 19.98 & 1.07 \\ \hline \hline \end{tabular} \({}^{1}\) Coefficient of variation.  
\end{table}
Table 5: Compressive strength data of different RM-type mortar specimens.  
Figure 7: SEM images of (**a**) SC100, (**b**) SC80 RM20, and (**c**) SC80 NTRM20 on the first day.  
distribution in SC100. A previous study [32] reported that pores with sizes larger than 50 nm affected the compressive strength of mortar. Pores with sizes larger than 50 nm were found to have the largest distribution in SC80 NTRM20, followed by SC80 RM20 and SC100. This result was found to be closely related to the results obtained while testing the compressive strength of mortar.  
The pore volume of SC80 RM20 was the lowest in the 1000-10,000 nm range. As RM had many particles with 1000-10,000 nm sizes, it appeared that these particles exhibited the pore filling effect [4; 10]. SC80 NTRM20 also had the lowest pore volume among the three mortar specimens in the 10,000-100,000 nm range, where the particle size distribution was the largest. [PERSON] et al. [21] reported that the porosity of mortar decreased because of the pore filling effect of RM microparticles, and this effect was larger for bigger pores.