Asphalt paver

A paver (paver finisher, asphalt finisher, paving machine) 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 paver was developed by Barber Greene Co., that originally manufactured material handling systems. In 1929 the Chicago Testing Laboratory approached them to use their material loaders to construct asphalt roads. This did not result in a partnership but Barber Greene did develop a machine based on the concrete pavers of the day that mixed and placed the concrete in a single process. This setup did not prove as effective as desired and the processes were separated and the modern paver was on its way. In 1933 the independent float screed was invented and when combined with the tamper bar provided for uniform material density and thickness. Harry Barber filed for a patent a "Machine for and process of laying roads" on 10 April 1936 and received patent U.S. Patent 2,138,828 on 6 December 1938. The main features of the paver developed by Barber Greene Co. have been incorporated into most pavers since, although improvements have been made to control of the machine.

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.

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