## 3 Results
### Slump Values and Air Contents  
The slump test results for the rural-road pavement concrete made with the air-cooled slag aggregates are shown in Figure 2. The slump value decreased with increasing air-cooled slag aggregate content, from 97.25 for the Plain to 94.25, 90.25, 87.00, and 85.25 mm for the GS 50%, GG 50%, GG 100%, and GS 50%/GG 100% mixes, respectively. The reduction in slump value was due to greater water absorption by the air-cooled slag aggregates because of their greater surface porosity. Not surprisingly, mixes containing the coarse air-cooled slag aggregate returned higher slump values than the corresponding mixes made with the fine aggregate. The air-content ratio was used to evaluate the effect of substitution ratio of the air-cooled slag aggregates on slump. The Plain, GS 50%, GG 50%,  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Item** & **Cd** & **Pb** & **Cr\({}^{+6}\)** & **As** & **Hg** & **Se** & **F** & **B** \\ \hline Elution standard & 150 & 150 & 250 & 150 & 15 & 150 & 4000 & 4000 \\ Value & 0.9233 & ND & ND & 0.3 & ND & 3.633 & 107.17 & 68.61 \\ \hline \end{tabular}
\end{table}
Table 13: Results of heavy-metal leaching test according to the waste-management law (unit: mg/L).  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Item** & **Pb** & **Cu** & **As** & **Hg** & **Cd** & **Cr\({}^{+6}\)** & **CN** \\ \hline Elution standard & 3 & 3 & 1.5 & 0.005 & 0.3 & 1.5 & 1 \\ Value & ND & 0.0012 & ND & ND & ND & ND & 0.0025 \\ \hline \end{tabular}
\end{table}
Table 13: Results of heavy-metal leaching test according to the waste-management law (unit: mg/L).  
GG 100%, and GS 50%/GG 100% mixes had slump values of 1.00, 0.97, 0.93, 0.89, and 0.88, respectively. It was evident that the slump value decreased with an increasing substitution ratio of the air-cooled slag aggregates. The GS 50%/GG 100% mix gave the greatest reduction (12%) compared with the Plain mix. The slump value affects workability, and an appropriate amount of slump is necessary in the field. Our target minimum slump value of 80 mm was satisfied by all of the mixes, and so we do not expect any workability issues with use of these mixes in field applications of rural-road pavement concrete containing air-cooled slag aggregates. Figure 3 shows the air-content test results for the rural-road pavement concrete. The air content increased with increasing air-cooled slag aggregate fraction, as follows: from 4.66 for the Plain to 4.86, 5.03, 5.27, and 5.39% for the GS 50%, GG 50%, GG 100%, and GS 50%/GG 100% mixes, respectively (Figure 3a). This trend was attributed to the greater surface porosity of the air-cooled slag aggregates. Additionally, the values for mixes containing the coarse air-cooled slag aggregate were much higher than those of the corresponding mixes made with the fine aggregate. This result was attributed to the coarse aggregate having a greater surface porosity than the fine aggregate. The air content for all of the test mixes satisfied this requirement. The air-content ratio was defined as the ratio of the air content of the mix containing an air-cooled slag aggregate to that of the Plain mix containing conventional aggregate. The Plain, GS 50%, GG 50%, GG 100%, and GS 50%/GG 100% samples had air content ratios of 1.00, 1.04, 1.08, 1.13, and 1.16, respectively (Figure 3b). The presence of air-cooled slag aggregates increased the air content relative to the Plain mix.