Asphalt & Bitumen West Co .

Asphalt along with emulsion bitumen

A: Artificial hot-mix asphalt with emulsion bitumen
The production of hot-mix asphalt with emulsion bitumen is similar to the production of hot-mix asphalt with pure bitumen but there are some differences:
1. The time of mixing is lower when using emulsion bitumen along with stone materials.
2. The required temperature for producing is lower than its level when using pure bitumen in producing hot-mix asphalt. 
3. Since fumes are arising from the water that exists in the emulsion bitumen, the hardening of it is less.
4. The time that is waste between loading and overlaying must be too short and it should happen before emulsion bitumen cracks.
B: Artificial cold-mix asphalt with emulsion bitumen
In this method, stone materials are produced along with emulsion bitumen at the asphalt factory. This type of cold-mix asphalt can be stored in a short time or it can get distributed after production. Because of its temperature, this type of asphalt can get carried in long distances. This type of asphalt is used in black base, binder, and Topeka.
This type of asphalt is eco-friendly, cheap, and more affordable since the required equipment and gadgets for its production are less than the others.
The techniques of applying cold-mix asphalt are similar to hot-mix ones. The block base layers can also be overlaid by the special overlaying machinery. The cold-mix asphalt especially the open-graded mixture is less practical compared with the hot-mix asphalt. If the surface stripping happens, the problem can be fixed at the factory by setting the mixing time and the ratio of emulsion to water or the quantity of them. Heating up the 
paving auto-machine doesn’t usually fix the problem but oiling it with gasoline helps a bit.
Cold-mix asphalt can be produced in layers with a thickness of 75 mm (or even thicker) based on the size of the biggest stone grain. However, hardening and manufacturing of fifty-seventy five millimeter-thick layers are done so much faster. Sometimes in order to implement cold-mix asphalt with high thickness, asphalt mixes are aerated. Therefore, it’s possible that the implementing thick layers leads to non-uniformity of the applied mixture. The breakage of open-graded cold-mix asphalt’s emulsion bitumen usually happens during the applying of the asphalt mixture. The breakage of dense-graded cold-mix asphalt happens a bit later than its applying compared with the open-graded mixtures. Also, because of the fact that more water is used in mixing the dense-graded mixtures, the rolling process is delayed until the mixture become resistant. The faster the water is imparted from the mixture, the faster the mixture can become dense. Therefore, using an amount of Portland cement in the mixture will make the manufacturing process faster. For primarily rolling the open-graded cold-mix asphalt, steel wheel rollers are used and for dense-graded cold-mix asphalt, vibratory rollers or tire rollers are used.
It should be considered that rolling a lot using the vibratory rollers makes the bitumen and water get separated from each other in the dense-grader cold-mix asphalts. In the middle of the process, you can use tire rollers or steel wheel rollers. steel wheel rollers are usually used for the ending rolling. Before primarily rolling the open-graded cold-mix asphalt, a small amount of filler material (about 3 or 5 kilograms per square meter) is implemented uniformly on the road surface. These filler materials can be the coarse dry sand along with the materials that are passed through the No 10 sieve (2 mm) due to the primary manufacture of open-graded stone materials. Filler stone materials prevent asphalt mixture from separating arising from traffic or rolling.
Precautions for manufacturing artificial cold-mix asphalt
• Dense-graded cold-mix asphalt with emulsion bitumen is usually durable against water during implementation.  However, during rain and before condensation and 
the manufacture of these mixtures, vehicle traffic must be controlled until achieving the suitable condensation.
• The amount of water that is mixed has to be as much as the bitumen emulsion needs to spread uniformly and reach the suitable efficiency. Severe use of water can cause a delay in implementation and rolling process.
• The mixing time has to be as much as allows the bitumen emulsion to spread uniformly in the mixtures. Long-term mixing can make the stone materials get rid of bitumen emulsion or it can cause breakage in bitumen emulsion.
• To get the implementation of cold-mix asphalt as soon as possible, the bitumen emulsion is manufactured in several thin layers.
• The surfaces of cold-mix asphalt shouldn’t be waterproofed too soon because it shuts the water in it can cause problems.
• If pavement stripping happens due to vehicle traffic, the removed materials should be cleared from the path in order to prevent any more pavement damages. If the amount of stripped sand increases, a thin cover of %15 bitumen emulsion and %85 water should be used to help the pavement heal better.
Specifying the type and the class of emulsion bitumen that has to be used and the manufacture of stone materials are done in a laboratory. The type of the used emulsion bitumen depends on the characteristics of stone materials, climate, pavement type, and the used machinery. MS-2, MS-2h, HFMS-2, HFMS-2h, CMS-2, CMS-2h are usually used for open-graded cold-mix asphalts in place. The temperature level of spreading bitumen emulsions in manufacturing cold-mix asphalts is from 20 to 70 degrees Celsius.
C: In-situ cold-mix asphalt with emulsion bitumen
Before overlaying in-situ cold-mix asphalt, the road surface should be cleared from any dirt and loose or removed grains and its roughnesses have to get fixed. Then the surface has to get condensed. If in-situ cold-mix asphalt is overlaid on a sandy surface, the road surface should be prepared by a prime coat and if the in-situ cold-mix asphalt is overlaid on the asphalt surface, the road surface should get tack coated before the in-situ cold-mix asphalt overspreads. In this method, stone materials of cold asphalt are usually the same materials that are used on the road surface or the materials that are carried to the place and windrowed or piled on the prepared road surface as much as needed. The size of the windrow and the distance between the piles should be in a way that lets you determine the amount of emulsion bitumen that overspreads on it in order to calculate the required thickness on the way and after combining with bitumen emulsion and in-situ cold-mix asphalt overspread. In such cases that we use the stone materials that exist on the road surface for manufacturing in-situ cold-mix asphalt, first, we have to plow the road surface to the maximum depth of %25 more than the thickness of the asphalt. Its width should be 6 meters more than the width of both sides of the road. Then the plowed materials are combined as well to gives us some uniform materials. The coarse particles of stone materials with a size of more than 3.6 centimeters (5.2 inches) should get removed from the road surface. Whenever the amount of stone material is not enough to make in-situ cold-mix asphalt, the lacking amount of material should be added to it and get mixed with each other well to match the grading of the mixed stone materials with the intended grading of stone materials of the in-situ cold-mix asphalt. The required emulsion bitumen is distributed on the stone materials using a bitumen distributor machine. To determine the needed amount of emulsion bitumen first we have to determine the volume of piled or windrowed stone materials per meter of the road length. Then based on the volume of windrowed stone materials, the percentage of bitumen emulsion should be measured per meter of the road and the speed of the spreader. This method is just like the method mentioned in paragraph “B”. But the difference is there is no factory here and the stone materials are windrowed on the road or piled near the road and then, the emulsion bitumen is poured on it and mixed by path constructing machinery such as loader and grader. This method is very useful for the roads that have low vehicle traffic or rural routes. It is worth mentioning that like the above methods the stone materials should have appropriate technical specifications.

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