# Freezing and Thawing Processes of Highways in Kazakhstan
## 4 Conclusions  
The following conclusions can be drawn from the analysis of the results obtained:  
1. The measuring stations used in the work make it possible to carry out long-term continuous monitoring of temperature and moisture in pavement and subgrade of highways. The results obtained are very important for road science and practice.
2. In the upper part of the pavement (up to 30-40 cm), the temperature changes in annual and daily cycles. As the depth increases, the daily temperature fluctuations disappear, leaving only the annual fluctuation. At a depth of 180 cm and below, temperature fluctuations occur only in the annual cycle.  
Figure 12: Combined graphs of moisture and temperature changes at a depth of 111 cm in the subgrade.  
Figure 13: Moisture distribution curves in pavement and subgrade at different characteristic times.  
3. During the cold period under consideration, on the selected section of the highway, the freezing process proceeded according to a complex pattern. The freezing rate varied from 14 cm/day to 0.33 cm/day. The maximum freezing depth was 227 cm.  
The thawing process has a simpler pattern. In this case, both \"bottom-up\" and \"top-down\" thawing take place. They begin at approximately the same time points. The descending branch of thawing occurs almost uniformly, with an average rate of 6.25 cm/day to a depth of 220 cm; the average rate of the ascending branch of thawing is 0.9 cm/day.  
Asphalt-concrete layers of the pavement and the upper part of the subgrade were in a frozen state for 151 and 166 days, respectively.  
1. In the subgrade at the beginning and end of the cold period (when the temperature has a value of approximately 0 \({}^{\circ}\)C), there are abrupt changes in moisture, which are explained by phase transitions of the second order: the transition from the liquid state to the solid (ice) at the beginning of the cold period and the transition of moisture from the solid state to liquid at the end of the cold period.
2. In autumn, on the surface of the subgrade, the moisture is 14%. It increases unevenly to a depth of 180 cm, at which reaches its maximum value (30-31%), then to a depth of 300 cm, and it decreases evenly to a value equal to 16-17%. In spring, on the surface of the subgrade, the moisture content is 10-12%. At depths of 78.111, 145, and 180 cm, it has a value equal to 11%, 19%, 18%, and 26%, respectively. In winter, due to the phase transitions in the subgrade, the moisture changes from 5% (on the surface of the subgrade) to 9% (at a depth of 145 cm).  
Conceptualization, B.T. and K.A.; methodology, B.T. and K.A.; investigation, B.T., K.A., C.O.R., E.S. and A.N.; writing--original draft preparation, K.A., E.S. and A.N.; writing--review and editing, B.T., E.S. and C.O.R.; visualization, E.S.; supervision, B.T., K.A. and A.Y.; project administration, A.Y. and E.S. All authors have read and agreed to the published version of the manuscript.  
The work was carried out within the framework of the topic \"Experimental research for the temperature and moisture distribution in pavement and subgrade of highways in various Kazakhstan regions\". It is funded by the \"National Quality Center for Road Assets\" of Road Committee of Ministry of Industry and Infrastructure Development of the Republic of Kazakhstan. Contract No. 190540022580/210222/00 dated 11 February 2021.  
Not applicable.  
The authors declare no conflict of interest.