Emulsion Bitumen in Protective Coatings

Roads that have suffered damage to the road surface due to weather and wear and tear, but whose substructure remains intact, require urgent repair operations so that the damage does not penetrate the substructure and cause its complete collapse. These damages mainly include small cracks in the road surface, loss of materials or abrasion of the surface. Until now, emulsion bitumen in protective coating as slurry seal, which is a mixture of bitumen and granular materials (gravel and filler), has been used to build such roads. Slurry seal operations:

1- Very small cracks and holes are filled with slurry seal.

2- These surfaces have a thickness of less than 8 mm and with this thickness, the surface will not be uniform.

3- If the surface is polished and slippery, the coefficient of friction of the road surface cannot be increased much with slurry seal.

4- Renewal and restoration of road gradients with slurry seal will not be possible. To compensate for the above shortcomings and to improve the desired condition of roads with high damage intensity but limited damage to the surface, thin asphalts with a maximum thickness of 10 mm are also applied, which can be considered an evolved type of slurry seal, which are introduced for emulsion bitumen in protective coating as below:

Emulsion Bitumen in protective coating as Micro Surfacing

Emulsion bitumen in protective coating as Micro surfacing is a mixture of bitumen emulsion and stone materials, which has the following characteristics:

1- Their stone materials are usually selected from 0-4 to 0-10 mm granulations, depending on the required thickness. Materials are selected from crushed stone materials as much as possible to provide better adhesion and to provide the necessary foundation for the road.

2- Due to the use of bitumen emulsion and a percentage of water, it has a fluid state (like concrete with a relatively high percentage of water) when spreading and is easily spreadable.

3- The final thickness will be in the range of 8 to 15 mm (depending on the type of granulation selected).

4- After application, it forms an almost impermeable layer. 5- If completely broken and resistant materials are selected, a surface with a high friction coefficient is created that also adheres well to the underlying layer.

The main applications of thin emulsion asphalts as emulsion bitumen in protective coating are in the following cases:

1- Roads that have suffered from cracking due to oxidation of the bitumen due to wear.

2- Surfaces that are separating from the road surface due to reasons such as reduced adhesion of the bitumen to the stone aggregates and need to be stabilized and protected in some way. 3- Surfaces that have lost their transverse slope to some extent and can be re-sloped by applying a layer of about 1.5 centimeters.

4- Roads that have been subjected to erosion or their surfaces have been polished and the road has become slippery.

5- Roads that have undergone wheel slippage, in which a larger amount of emulsion asphalt is poured to compensate for future slippage.

Choosing a Bitumen Emulsion

When choosing the type of emulsion (cationic or anionic), the following points should be considered for emulsion bitumen in protective coating:

1- The bitumen emulsion should be as even as possible with the components in terms of surface charge in opposite directions (positive and negative) so that sufficient adhesion is created between the components and the bitumen before the water breaks and separates from the bitumen emulsion. If the minerals of a mineral are of different types and their mixture contains both positively and negatively charged minerals, it is better to use cationic emulsions.

2- The time for breaking the emulsion should be consistent with the expected time for implementation so that the emulsion breaking operation is not performed before the end of the asphalt spreading operations. On the other hand, the failure time should not be so long that the road is closed to traffic for a long time.

3- The bitumen emulsion must be able to withstand unexpected weather conditions (humidity and rainfall) and the bitumen must not separate from the water before application.

Conditions for using emulsion bitumen

Since the effectiveness of thin emulsion asphalt mixtures is more in filling limited (shallow) cracks and holes, in order to remove such damage from the road surface, emulsion bitumen in protective coating recommended:

1- If the potholes in the road surface are small (depth between 2 and 4 cm), thin emulsion asphalt mixtures with grain sizes of 0-4 or 0-10 mm should be used.

2- If the potholes are larger or the road is deformed and wavy, hot asphalt coatings should be used or the deformations and waves should be removed first with asphalt grinders and then thin emulsion asphalt should be applied. Spreading ratio The spreading rate of thin emulsion asphalt on the road surface is determined by the condition of the existing surface, weather and water conditions, the season of operation, the type of emulsion and its bitumen percentage. However, the following values ​​can usually be used as a guide. Thin emulsion asphalt with a grain size of 0-6mm: 12-16 kg/m2 (dry material weight) Thin emulsion asphalt with a grain size of 0-6mm: 12-16 kg/m2 (dry material weight)

Limitations of the use of emulsion bitumen