Road structure – process – or apparatus – Process – In situ treatment of earth or roadway
Patent
1997-02-27
1999-04-20
Will, Thomas B.
Road structure, process, or apparatus
Process
In situ treatment of earth or roadway
404 79, 404 95, E01C 706, E01C 2314
Patent
active
058951717
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a process for heating an asphalt surface and to apparatus therefor.
BACKGROUND ART
As used herein, the term asphalt also comprises macadam and tarmac. Asphalt paved road surfaces typically comprise a mixture of asphalt cement (typically a black, sticky, petrochemical binder) and an aggregate comprising appropriately sized stones and/or gravel. The asphalt concrete mixture is usually laid, compressed and smoothed to provide an asphalt paved road surface.
Over time, an asphalt paved road surface can deteriorate as a result of a number of factors. For example, seasonal temperature fluctuations can cause the road surface to become brittle and/or cracked. Erosion or compaction of the road bed beneath the road surface may also result in cracking. Moreover, certain of the chemical constituents incorporated in fresh asphalt are gradually lost over time or their properties changed with time, further contributing to brittleness and/or cracking of the road surface. Where concentrated cracking occurs, pieces of pavement may become dislodged. This dislodgement can create traffic hazards, and accelerates the deterioration of adjacent pavement and highway substructure. Even if cracking and the loss of pavement pieces do not occur, the passage of traffic can polish the upper highway surface, and such a surface can be slippery and dangerous. In addition, traffic-caused wear can groove, trough, rut and crack a highway surface. Under wet highway conditions, water can collect in these imperfections and set up dangerous vehicle hydro-planing phenomena. Collected water also contributes to the further deterioration of the pavement.
Prior to about the 1970's, available methods for repairing old asphalt-paved road surfaces included: spot treatments such as patching or sealing, paving with new materials over top of the original surface, and removal of some of the original surface and replacement with new materials. Each of these methods had inherent drawbacks and limitations.
Since about the early 1970's, with increasing raw material, oil and energy costs, there has been a growing interest in trying to recycle the original asphalt. The world's highways have come to be recognized as a very significant renewable resource.
Early recycling techniques involved removing some of the original surface and transporting it to a centralized, stationary recycling plant where it would be mixed with new asphalt and/or rejuvenating chemicals. The rejuvenated paving material would then be trucked back to the work site and laid. These techniques had obvious limitations in terms of delay, transportation costs and the like.
Subsequently, technology was developed to recycle the old asphalt at the worksite in the field. Some such processes involved heating and are frequently referred to as "hot-in-place recycling" (hereinafter referred to as HIPR).
This technology comprises many known processes and machines in the prior art for recycling asphalt paved surfaces where the asphalt has broken down. Generally, these processes and machines operate on the premise of (i) heating the paved surface (typically by using large banks of heaters) to facilitate softening or plasticization of an exposed layer of the asphalt; (ii) mechanically breaking up (typically using devices such as rotating, toothed grinders; screw auger/mills; and rake-like scarifiers) the heated surface; (iii) applying fresh asphalt or asphalt rejuvenant to the heated, broken asphalt; (iv) distributing the mixture from (iii) over the road surface; and (v) compacting or pressing the distributed mixture to provide a recycled asphalt paved surface. In some cases, the heated, broken material can be removed altogether from the road surface, treated off the road surface and then returned to the surface and pressed into finished position. Much of the prior art relates to variations of some kind on this premise.
Over time, HIPR has had to address certain problems, some of which still exist today. For example, asphalt concrete (especially the asphalt ce
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Joharifard Mostafa
Wiley Patrick C.
Hartmann Gary S.
Martec Recycling Corporation
Will Thomas B.
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