8. Conclusion

According to Figure 15; the highest Von Mises tensions were occurred the coating layer and the lowest values were observed in the base layer. It is fixed that The Von Mises tensions increased in the coating layer within 1 year period. It has been determined that the highest Von Mises tension were in SK type road coating whereas, the lowest Von Mises tensions were in N type coating. The Von Mises tensions of base layer indicated similarity properties and no

Vertical deformation (y)-time changes of the super-structure of the road is given in Figure 16.

When Figure 16 is evaluated, it is seen that the highest vertical deformations are found at the base and lower base layers and the lowest deformations are found at the coating layer. Within a year, there have been small deviations in the amount of deformation. The amounts of deformation were confirmed as 0.014492 mm in SK-type, and 0.0145 mm in NK-type in the 12th month [34]. Von Misses stress and vertical deformation function and R2 values are submitted in Table 10.

Von Mises stress function R2 Vertical deformation function R2

3E-05x + 0,0059 0,9683 y = 0,0001x + 0,0199 0,9686

<sup>S</sup> y = 3E-05x2 + 0,003x + 0,0088 0,9583 y = 0,0001x + 0,0199 0,9329

<sup>N</sup> y = 0,0001x2 + 0,0019x + 0,0092 0,9095 y = 0,0001x + 0,0199 0,8744

3E-05x + 0,0059 0,929 y = 3E-06x2

–0,0047x + 0,0096 0,9282 y = 3E-06x2

–0,0001x + 0,0199 0,9678

–0,0002x + 0,02 0,8994

1E-04x + 0,0199 0,9301

9E-05x + 0,0199 0,8785

–0,0001x + 0,0199 0,9059

Figure 16. Vertical deformation (y)-time changes of the super-structure of the road [34].

Coating SK y = 0,0001x<sup>2</sup> + 0,0021x + 0,0101 0,977 y = 1E-06x<sup>2</sup>

NK y = 0,0099e0,1654x 0,9291 y = 8E-06x<sup>2</sup>

NK y = 7E-05x2 + 0,0003x + 0,0057 0,4428 y = 6E-06x<sup>2</sup>

significant changes were observed [34].

36 Modified Asphalt

Layer types Regression models Function type

Base SK y = 6E-07x<sup>2</sup>

<sup>S</sup> y = 4E-07x2

N y = 0,0012x2

It came out that the performance characteristics of the SBS-added the HMA are improved due to the use of the SBS polymer material as compared to the unmodified ones. This is because when the SBS polymer is used, the adhesion between the aggregates increases. It has been seen that the flexible structure of asphalt is stiffened due to environmental conditions due to oxidation, which is caused by temperature changes and precipitation during transportation, storage, mixing and production processes. In addition to, as the air void ratio increases, the hardening time decreases due to air contact. The hardening of the asphalt road coating was found to be higher in the coating without additive material and it was appeared that the polymer increased the deformation resistance at high temperatures and increased the tendency to fracture at low temperatures.

Analytical calculations from different material types and different strata in the flexible road coating are complex. The traffic loads and the distribution of pressure on the superstructures of the roads are varied, and different materials are used on each layer, and therefore the mechanical properties and the load distribution ability vary. Climate and various environmental conditions affect the road. Because of these reasons, empirical studies must be promoted with numerical analyzes to establish performance characteristics of the road.

### Acknowledgements

The author would like to thank Transportation Laboratory, Department of Civil Engineering, Firat University; Geotechnical &Transportation Laboratory, Department of Civil Engineering, Dicle University, Istanbul University and Bimtas Research Laboratories, Istanbul.
