# Effect of PVA/PVAc Based Polymer Coating on Dust Reduction in Playground
## 3 Results and Discussion  
### Soil Physical Properties  
Figure 6 displays the results of specific gravity and moisture content of various soil samples. Figure 6a depicts specific gravity of the soil samples. It is obvious from Figure 6a that the minimum specific gravity was presented by uncoated soil samples (2.612) while the maximum specific gravity was obtained for soil samples coated with 12% coating solution (2.685). A slight increment in specific gravity was perceived for coated soil samples in comparison with the uncoated soil samples. Additionally, specific gravity increased with the increase in the amount of coating solution. It may be attributed to the porous nature of pumice sand which absorbed a higher content of coating solution during the coating process [36; 37; 38]. Figure 6b shows the moisture content of the soil samples. From Figure 6b, it is clear that the moisture content decreased with the increase in coating solution content.  
Figure 4: Dust measurement setup due to wind effect (**a**) Front view and (**b**) Side view.  
Figure 5: Dust measurement setup due to human activity (**a**) Front view and (**b**) Side view.  
For instance, a moisture content of 16.5%, 15.8%, 15.2%, and 14.9% was measured for soil samples coated with 0%, 7%, 10%, and 12% coating solution. The reduction in moisture content is attributed to the reduced permeability due to its being coated.  
Soil changes from solid state to semi-solid or plastic or fluid state due to the presence of moisture content. The liquid limit represents the boundary between the liquid state and the plastic state. The plastic limit represents the boundary between the plastic state and semi-solid state. Figure 7 displays the liquid limit and the plastic limit of the soil samples coated with different percentages of the coating solution. The results clearly demonstrate that liquid and plastic limit values tend to decrease when there is an increase in the amount of coating solution. For instance, a liquid limit value of 27.8%, 27.2%, 26.5%, and 25.2% was noted for the soil samples coated with 0%, 7%, 10%, and 12% coating solution, respectively. A plastic limit value of 14.5%, 13.9%, 12.9%, and 11.7% was measured for the samples coated with 0%, 7%, 10%, and 12% coating solution, respectively. This reduction in liquid limit and plastic limit values can be explained by the reduction in moisture content of the soil samples.  
Figure 6: (**a**) Specific gravity and (**b**) moisture content of soil samples.  
Figure 7: Liquid limit (%) and plastic limit (%) values of soil samples.  
A field density test was conducted to evaluate the degree of compaction achieved during the construction procedure. If the field density results are more than 90% of maximum drying density obtained by indoor compaction test, it indicates proper compaction conditions. A field density measurement was conducted three times and an average value was reported. Table 3 summarizes the field density test results. The moisture content was measured in a range of 10.3% to 10.8%. The reduction in moisture content compared to the indoor measurement after the coating procedure may be due to the evaporation of moisture during site construction. The degree of compaction was calculated as a percentage of the maximum dry density for field dry density, and all three results exceeded the Korean standard of 90%. The experimental results show that the coated soil specimen is suitable to be used as a surface layer material for the playground.