How to harden asphalt millings
How To Harden Asphalt Millings- The pressure of the defective pavement layer with preliminary heating of the surface is called hot milling, without warming up – cold milling. The main advantage of hot milling is the less effort required to break the coating being removed. This method also has disadvantages: the destroyed material sticks together, it is difficult to reuse or transport it, when operating machines there is a risk of fire, etc., and therefore cold milling machines are most popular among road workers.
Cold milling machines have an additional advantage: when milling, old asphalt concrete is transformed into free-flowing building material – granules, consisting of pieces of a strictly defined size, which can be reused. Just in the 1960s and 1970s, the recycling of materials was gaining popularity, and the useful use of construction waste turned out to be very useful. The ministries of transport and highways of many countries immediately drew attention to this type of equipment, and soon there were modifications of machines that we’re able to carry out cold milling of the old road surface, mix the resulting material with a fresh binder, and lay the prepared mixture on the milled surface, thus completing the process of restoring the roadway.
With wear and tear, the road surface becomes smooth and slippery, which sharply increases the likelihood of accidents. Cold milling cutters allow you to create a rough-textured surface.
Milling asphalt concrete pavement: improving technology
The main focus of the design improvement was on increasing the productivity of the milling drums. Working bodies – the cutters wore out quickly, and they had to be replaced often, which was a serious problem. The replacement process took a long time, and cold milling cutters were taken out of work for a long time, which dramatically reduced productivity. Therefore, all manufacturers have sought to speed up the replacement process and increase the life of these parts. Wear-resistant steels were selected for their manufacture, and the shape of the cutting edge was improved.
In modern cold milling machines, the tool holder has also been improved. On the first machines, the cutters were attached to the drum by welding, so it took a long time to replace them. In modern machines, the cutters are bolted into different tool holders, which significantly reduces the time required to replace them. However, some drums for cold milling of relatively soft asphalt surfaces retain weldable tool holders. Later, a technique appeared with replaceable milling drums of different widths, which made it possible to change the width of the cold milling strip of the roadway.
The wear of the cutters depends on the hardness of the material and the amount of work. As the milling depth increases, the amount of work for the cutters increases disproportionately. The cutters are mounted on a circular drum and cut the material in an arc. Cold milling to a depth of 102 mm is associated with a cutter path length that is twice as long as at a shallower milling depth – 25 mm (the difference in depth is four times).
Basically, cold milling cutters are classified into small and large. The width of the milling area for small models ranges from 300 to 1200 mm; the milling depth is up to 100 mm. They are small and highly maneuverable. A special feature of these machines is the location of the milling drum between the rear axle wheels.