## 3 Results and Discussion  
Figure 2 presents the results of the dust emission experiment. The recorded PM10 concentrations are a result of dust emission from the surface of the loess soil samples under two wind velocities. It is clearly shown that no dust emission and PM10 concentration was recorded in the application of the clay-based geopolymer. The \"straight\" line that was similarly recorded for the two wind velocities in the test of the geopolymer application is a representation of the background level (\(\sim\)20 \(\mu\)g m\({}^{-3}\)) measured in the wind tunnel before the test. In all the other applications, bitumen, brine and PVA, the averaged PM10 concentrations were significantly (\(p<0.05\)) higher than the background level. In general, the PM10 concentrations received for the brine, PVA, and bitumen, were higher under 9 m s\({}^{-1}\) compared with 6.5 m s\({}^{-1}\). The wind velocity OF 9.5 m s\({}^{-1}\) was run promptly after the prior velocity (6.5 m s\({}^{-1}\)), and since the amount of dust particles in the soil samples is limited, the dust emission in 9.5 m s\({}^{-1}\) could have been an underestimation for non-limited samples. The PM10 values of the control sample were significantly higher than those of all the other samples in both wind velocities, suggesting that all the applied products are efficient for dust suppression at a certain level. It is interesting to see that the brine, which was found to be very efficient by reducing \(>90\%\) of the dust emission in calcareous soils under the same experimental conditions [8], is less effective in loess soils. The results of the brine are at the range of the PVA. However, the brine is not used for the purpose of soil stabilization as the PVA and the geopoylmers. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Geopolymer Composition** & **MK (\%)** & **Activation Solution** \\ \hline Group 1 & 0, 2.5, 5, 5, 7.5, 10, & sodium silicate (Na\({}_{2}\)SiO\({}_{3}\)) and sodium hydroxide (NaOH) \\ Group 2 & 30 & sodium silicate (Na\({}_{2}\)SiO\({}_{3}\)) and calcium oxide (CaO) with ratio of 1, 5, 10, 15, 20. \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The compositions of the geopolymer as a loess soil stabilizer used for the tensile strength test. Group 1: different MK content (%) with a constant activation solution of sodium silicate and NaOH. Group 2: different concentrations of CaO as a replacement to the NaOH in the activation solution with MK content of 30%. Tensile tests were conducted for the geopolymer as a soil stabilizer. The first test was to examine the effect of the MK amount at the range of 0-30% in the geopolymer composition (Group 1, Table 2). The activation solution (sodium silicate and NaOH) remained in a constant ratio. The results in Figure 3a show that the soil sample without MK (0%) resulted in resistant of less than 1000 N. Application of MK content at the range of 2.5-10% improved the soil resistant up to 6000 N. A significant change was obtained for samples with MK content at the range 20-30%. These samples resulted in a consistent increase in resistance to pressure when the peaks ranges from \(\sim\)11,000 N (20% MK) to \(\sim\)25,000 N (30% MK). Just for comparison, we tested also the PVA as soil stabilizer, which has been used extensively in soil stabilization [22]. The PVA results after a curing time of 28 days were up to 4200 N. The drying time until significant strength is reached is an important factor when there is a need to stabilize an unpaved road. External factors, such as solar radiation and water regime, can have a great impact on the nature and duration of the soil stabilization. As such, this study examined the hardness of the geopolymer during a short seven-day cure. The geopolymer composition of 30% MK with the activation solution (sodium silicate and NaOH) yielded a result of 15,510 N.  
A second tensile test was conducted for geopolymer with replacement of the NaOH with the base of lime (CaO) that is more \"natural\" soil material (Group 2, Table 2).