عنوان مقاله [English]
نویسنده [English]چکیده [English]
To make the slippery roads surfaces safe during the winter, highway authorities usually must either apply rock salt (NaCl) or other chemical de-icers to melt ice and snow or spread sand to provide traction. Since usage of these materials may have negative environmental and physical impacts, therefore, their properties must be known to provide adequate space for improvement and to compensate for any short comes.
In this research we are only concerning with the physical impact of the issue which is lowering skidding resistance of the surface as a result of applying rock salt to melt the snow and ice.
Road surface type snow and ice melt more rapidly on a concrete surface because it gives up heat more rapidly. Since asphalt absorbs more solar radiation, it is therefore have more heat available for melting snow. This is why snow melts rapidly next to bare asphalt pavement areas. Even when the temperature of the pavement is below freezing point, it holds some heat and can help melting snow and ice.
Changing ice or snow into water (brine) requires heat from the air, the sun, the pavement, or traffic friction. The surface temperature of a snow- or ice-covered road determines de-icing salt amounts and melting rates. As temperatures go down, the amount of salt needed to melt a given quantity of ice increases significantly. Using salt brine to pre-wet is becoming more common because of its lower cost.
In this research it was established that the presence of salt brine on the surface will lower down the skidding resistance of the surface considerably. It is necessary to have adequate drainage system on the roads that enables the melted snow and ice which have concentration of high amount of salt content to be clear off the surface as soon as possible. It is better to apply salt as needed than to over-treat initially.
It has been established that on the location in which the harsh maneuvering, acceleration and deceleration is needed aggregate of higher Polished Stone Value (PSV) be used than it was believed to be used before.