COLD MILLING MACHINE
A milling machines or cold planers use a large rotating drum to remove and grind the road surface. The drum consists of scrolls of tool holders. The scrolls are positioned around the drum such that the ground pavement is moved toward the center and can be loaded onto the machine’s conveyor belt. The tool holders can wear out over time and can be broken while milling if highway structures like manholes are encountered while milling.
The tool holders on the drum hold carbide cutters. The cutters can be removed and replaced as they wear out. The amount of wear (and therefore the interval between replacement) varies with the type and consistency of the material being milled; intervals can range from a few hours to several days.
The drum is enclosed in a housing/scrapper that is used to contain the milled material to be collected and deposited on the conveyor. The spacing of the tool spirals around the drum affect the end surface of the road, with micro-milling having the tightest spacing.
The majority of milling machines use an up-cut setup which means that the drum rotates in the direction opposite that of the drive wheel or tracks, (i.e. work surface feeds into the cut). The speed of the rotating drum should be slower than the forward speed of the machine for a suitable finished surface.
Modern machines generally use a front loading conveyor system that have the advantage of picking up any material that falls off the conveyor as milling progresses. Water is generally applied to the drum as it spins, because of the heat generated during the milling process. Additionally, water helps control the dust created. In order to control the depth, slopes, and profile of the final milled surface many millers now have automatic depth control using lasers, string-lines, or other methods to maintain milled surfaces to ±5 mm (0.20 in) of the target height
A asphalt- paver is a piece of construction equipment used to lay asphalt on roads, bridges, parking lots and other such places. It lays the asphalt flat and provides minor compaction before it is compacted by a roller.
The asphalt is added from a dump truck or a material transfer unit into the paver’s hopper. The conveyor then carries the asphalt from the hopper to the auger. The auger places a stockpile of material in front of the screed. The screed takes the stockpile of material and spreads it over the width of the road and provides initial compaction.
The paver should provide a smooth uniform surface behind the screed. In order to provide a smooth surface a free floating screed is used. It is towed at the end of a long arm which reduces the base topology effect on the final surface. The height of the screed is controlled by a number of factors including the attack angle of the screed, weight and vibration of the screed, the material head and the towing force.
To conform to the elevation changes for the final grade of the road modern pavers use automatic screed controls, which generally control the screed’s angle of attack from information gathered from a grade sensor. Additional controls are used to correct the slope, crown or superelevation of the finished pavement.
In order to provide a smooth surface the paver should proceed at a constant speed and have a consistent stockpile of material in front of the screed. Increase in material stockpile or paver speed will cause the screed to rise resulting in more asphalt being placed therefore a thicker mat of asphalt and an uneven final surface. Alternatively a decrease in material or a drop in speed will cause the screed to fall and the mat to be thinner.
The need for constant speed and material supply is one of the reasons for using a material transfer unit in combination with a paver. A material transfer unit allows for constant material feed to the paver without contact, providing a better end surface. When a dump truck is used to fill the hopper of the paver, it can make contact with the paver or cause it to change speed and affect the screed height.
A tandem roller from 1.5 to 3 ton have compact dimensions, they are suitable for compacting asphalt in car parks, bike paths and road construction. Combine high compaction performance with small dimensions and great visibility.
Large tandem rollers of 6 to 11 tonnes are suitable for large motorway works where precise rules for compaction of road surfaces or for large squares in industrial areas are in place.
SINGLE DRUM ROLLER
Small and medium-sized single drum rollers weighing between 6 and 9 tonnes are distinguished by the width of the drum min. 1,4 to max 1,7 m.
They are equipped with two or more vibrations and are suitable for small / medium jobs in urban and industrial areas. They can be equipped with padfoot drum (or padfoot shells that apply to the smooth drum) to compact the clay soils.
Medium-to-large single drum rollers weighing from 10 to 24 tons are distinguished by the width of the drum from min 2 to 2.2m.
They are generally equipped with many vibrations and for heavier, even specific options for compaction tests. They are suitable for large freeways detected. They can be equipped with padfoot drum (or padfoot shells that apply to the smooth drum) to compact the clay soils.
RUBBER TYRED ROLLER
The rubber tyred rollers, consist of a heavily-loaded wagon with several rows of closely-spaced tyres. They provide uniform pressure throughout the width covered, and are often used in pavement subgrade works, as they are suitable for compacting uniform coarse soils and rocks. They are also used to finish embankments compacted by sheepsfoot rollers
The factors which affect the amount of compaction that can be achieved are the weight, tyre inflation pressure and the area of contact.
A soil stabiliser is a construction vehicle with a powered metal drum that has rows of mixing blades or paddles. It makes soil cement by blending soil, a binder agent (usually Portland cement or lime) and water together with paddles in the mixing chamber instead of a concrete mixer and usually does not cut or mill hard or very thick asphalt or concrete. Modern soil stabilisers are more powerful and often use carbide tips instead of paddles. Some are called single pass soil stabilizers because they can make soil cement in one pass where some of these machines take up to four passes. In this way most soil stabilisers have become much more like road recyclers where they can also blend the old road surface in the mixture.
Asphalt distributors are used to apply prime or tack coats on a surface in preparation for paving. They are available in either truck mounted or trailer models and are considered the most important piece of equipment on any asphalt surface treatment project. It consists of an insulated tank with a heating system, a spray bar and unique control system.Application of a prime or tack coat by the distributor is an exact science that requires sophisticated equipment to ensure it produces a uniform spray.
A motor grader, is a construction machine with a long blade used to create a flat surface during the grading process. Typical models have three axles, with the engine and cab situated above the rear axles at one end of the vehicle and a third axle at the front end of the vehicle, with the blade in between. In certain countries, for example in Finland, almost every grader is equipped with a second blade that is placed in front of the front axle. Some construction personnel refer to the entire machine as “the blade”. Capacities range from a blade width of 2.50 to 7.30 m and engines from 93–373 kW (125–500 hp). Certain graders can operate multiple attachments, or be used for separate tasks like underground mining.