# Freezing and Thawing Processes of Highways in Kazakhstan
## 2 Research Background and Method  
In the Republic of Kazakhstan, for an experimental study of the water and heat regime of highways during 2020-2021, 28 measuring stations equipped with temperature and moisture sensors were installed all over the country (Figure 1). Temperature and moisture sensors were installed along vertical wells at different depths (Figure 2a). The pavement structure with the locations of the sensors on the road section near Kostanai is shown in Figure 2b. Sensors measured temperature and moisture data every hour in an automatic regime. Additionally, an air-temperature-measuring sensor was installed on the mast of the GPGS transmitter at a height of 2 m from the ground surface (Figure 2). All measured data were transmitted via GPGS to a special website, from whichthey weredownloaded to the database of the Kazakhstan Highway Research Institute (KazdonNII). Temperature and moisture sensors were supplied by Real Style Co. (Kostanay, Kazakhstan). The measuring stations were assembled at the KazdorNII, together with Real Style Co.  
In this article, the northern region of Kazakhstan (Kostanai, Pavlodar) with the longest cold climate was chosen for the experimental study of freezing and thawing processes.  
Graphs showing changes in temperature and moisture are built on the basis of data received directly from the measuring stations. Graphs of the depth of freezing and thawing are built, also using the temperature values obtained from the measuring stations. At the same time, it was assumed that the pavement materials and subgrade soils begin to freeze even at a temperature of 0 \({}^{\circ}\)C.  
Figure 2 shows the external view of the transmitting antenna and the schematic view of the pavement structure with sensors' location depths.  
The road structure consists of three layers of asphalt concrete, a layer of a mixture of crushed stone, gravel and sand, sand soil, and black soil. Names of materials for structural layers and their thickness are given in Table 1. The values of optimal moisture content (W\({}_{\text{opt}}\), %), maximum density (\(\rho_{\text{max}}\), g/cm\({}^{3}\)), and plasticity number (I\({}_{\text{p}}\), %) of soils are as follows: sandy loam--1.88; 16.2; 11.4, respectively; black soil--1.81; 16.3; 15.8, respectively.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Name of Materials for Structural Layers and Soils** & **Layers Thickness, cm** \\ \hline Fine-grained (20 mm) dense asphalt concrete & h\({}_{1}=5\) \\ Coarse-grained (40 mm) porous asphalt concrete & h\({}_{2}=13\) \\ Coarse-grained (40 mm) high porous asphalt concrete & h\({}_{3}=9\) \\ Mixture of crushed stone, gravel, and sand (80 mm) & h\({}_{4}=35\) \\ Sandy loam & h\({}_{5}=90\) \\ Black soil & h\({}_{6}=148\) \\ \hline \hline \end{tabular}
\end{table}
Table 1: Materials for structural layers and soils.  
Figure 1: Map of locations of measuring stations on the territory of Kazakhstan.  
Figure 2: (a) External view of the measuring stations across Kazakhstan; (b) schematic view of the pavement structure with sensors’ location depths; 1–3—asphal concretes; 4—mixture of crushed stone, gravel and sand; 5—sand; 6—black soil.