Resumen
The paper presents the analysis of pavement temperatures from meteorological stations located at the Polish national roads during the impact of low winter temperatures. Presented issue is particularly important in view of the problem of low-temperature cracks that occur in the asphalt pavement under the influence of low temperatures. For each location of meteorological station there were analysed measurements of the temperature on the road pavement surface, at depth of 5 cm and 30 cm in the pavement structure and air temperature 20 cm above the pavement surface. The analysis of the data included determination of minimum surface temperatures, duration of low temperatures, distributions of temperatures at the depth of pavement structure and the rate of cooling of the pavement surface. The number of temperature transitions for a specified level of low temperatures: 0 °C, -5 °C, -10 °C, -15 °C and -20 °C were also determined. It was found that the longest uninterrupted period of surface temperature hold below -20 °C is 18 hours, but below -15 °C is already 85 hours. On the basis of the distributions of temperature at the depth of pavement structure it was found that the recorded values of the minimum temperature of up to -25 °C on the surface of the asphalt pavement, the temperature at a depth of 5 cm, is higher by about 2?4 °C than the surface temperature, while at depth of 30 cm it is already higher by about 20 °C than the surface temperature. Another important factor affecting the performance of asphalt pavement and in particular the resistance to low-temperature cracking is the cooling rate. With increase of cooling rate during severe winter conditions the probability of low temperature cracking increase. It was found that the cooling rate of the asphalt pavement surface is up to 3 °C/h.