The asphalt surface of the roads can experience erosion, raveling, loss of aggregate,honeycombing, and sulphate attacks over time due to weather conditions such as frost, sunlight, heat, and also road salting, snow removal, as well as the effects of excessive loading and friction, especially caused by tire chains and snowplow blades. Failing to repair and install overlay asphalt in due time will allow damages to expand, leading to complete destruction of the road surface and even the underlying layers. The use of protective layers is recommended to prevent intensification of asphalt wear out, postpone overlay installation, maintain the existing conditions, and fill the cracks.
In addition to providing a suitable road surface, these layers will waterproof it and prevent the destruction of asphalt and its underlying layers. This is a cheap maintenance method that will ensure uninterrupted and secure operation of the roads. Different methods are recommended based on the degree of destruction, the weight and volume of traffic, and type of asphalt. These methods are inexpensive and can be employed early after or even before the beginning of asphalt pavement distress.
1. Fog Seal
Spraying bitumen emulsion without aggregates, aiming to revive asphalt layers. Fog seal can fill small cracks, help seal sand and gravel in the asphalt, and prevent honeycombing. Fog seal can be used in both high-traffic and low-traffic roadways, where depending on
the breaking time of the bitumen emulsion, the traffic must be avoided for 2-3 hours. Obviously, fog seal is not recommended for roads that are not cracked or porous.
It is better to apply fog seal during warm weathers, helping the existing water evaporate faster; of course, it can be installed in mild weathers. Its installation in cold weather will require longer periods for the water to evaporate and the emulsion to stick. At the time of installation the temperature of the bitumen emulsion must be between 50 and 70 degrees Celsius, while the asphalt surface must be at least 10 degrees Celsius. Fog seal is unable to fill long and deep cracks, and these should be patched beforehand. Fog seal can increase the lifespan of asphalt up to four years.
The amount of bitumen used in fog seal is 300 to 1200 grams per square meters, depending on the asphalt condition.
2. Seal Coat
Spraying bitumen emulsion with a layer of gravel atop it. Emulsions with longer breaking time should be used for sealcoating. In addition to creating a desirable surface, sealcoating can provide suitable friction properties and waterproof the asphalt. Seal coat can be used at any times, and for different degrees of pavement distress, however, a layer of fog seal is recommended before sealcoating. The best temperature for applying a seal coat is warm or hot weather. Humid and cold weather will increase the drying time needed before the traffic is allowed to pass, which in warm weather will take four hours at most. In terms of function, depending on climatic conditions and the volume of traffic, seal coated road will take up to six hours to be ready for operation. Sealcoating is recommended for low-traffic rural and secondary roads, and not for high-traffic main roads.
3. Surface treatment
In terms of installation, it is similar to sealcoating, except that surface treatment should be applied to the base, usually on Binder and Topeka layers, where the bottom layer is thick and the top layer is thin. Before applying the second layer, the loose materials of the first layer must be cleared away using compressed air. The price might vary depending on the spot price of bitumen and other materials, but it is incomparable with hot mix asphalt. It should be noted that the surface layer does not bear any loads, and the weight of vehicles is transferred to the bottom layers.