Road structure – process – or apparatus – Pavement
Reexamination Certificate
2000-09-25
2001-11-13
Will, Thomas B. (Department: 3673)
Road structure, process, or apparatus
Pavement
C404S107000
Reexamination Certificate
active
06315492
ABSTRACT:
The present invention relates to road surfacing materials and in particular their use in repairing holes in damaged roads.
Throughout this specification, the word road is intended to include paths, runways, driveways and any other similar hard topped surface.
Many road surfaces are covered with bitumen or concrete to provide a hard surface. Over time these surfaces may be damaged, leading to spalling of the surface, ‘pot-holes’ and cracking. Traditionally, road surfaces have been repaired by cleaning the damaged area and applying bitumen or concrete to the damaged part to provide a flat load bearing surface again. However there are drawbacks to both these repair methods.
Bitumen based material is prepared off-site where the bitumen is heated to a high temperature and then mixed with aggregate etc. The mixed material is then poured into silicon lined bags and allowed to cool into solid blocks. These bags are then sold to contractors, etc who transport them to the site of the repair. On site, the bags are then stripped off and the blocks are heated in a boiler until they soften. Due to the size of the blocks and the high volume to surface area ratio, the melting process is slow. Once melted, the mixture is then poured into the damaged part of the road to provide a repaired surface. The bags must then be disposed of.
There are drawbacks with this method of repair. The repaired section is not as strongly adhered to the base material as an undamaged portion of road is. Therefore, it is prone to deteriorate again. Also, particularly where the original surface is concrete, the repair is quite apparent because the black bitumen material stands out against the much paler colour of the concrete. This can be undesirable from an aesthetic point as well as in terms of visibility, for example on concrete roads or domestic driveways. It is very difficult to overcome this problem by colouring the bitumen due to the sheer blackness of the bitumen. Large amounts of colorant are needed and even so the results are often poor. Furthermore, the cost of manufacturing the bitumen blocks and subsequently having to heat them on site to a high temperature (around 200° C.) makes it expensive. Once on site it can take 2 to 3 hours to melt a block which results in wasted time. Alternatively, the contractor may start heating the bitumen prior to arrival on site, i.e. carrying hot melted bitumen whilst in transit, which is clearly quite dangerous.
Another alternative repair material is concrete. This is usually transported to site in a pre-mixed form which requires it to be used fairly quickly. This makes it inconvenient to use. Concrete repairs suffer from similar problems to bitumen in that the repaired section generally deteriorates faster than the unrepaired sections and thus requiring further repair. Generally when concrete develops pot holes or severe cracking the whole concrete bay is removed to the foundation and replaced with new concrete. The process is expensive and time consuming causing the road to be closed for several days.
One more recent alternative is to use a cold applied epoxy resin based repair material The raw materials can be easily transported to site and mixed there prior to use. However this is relatively expensive. Furthermore, this method is very sensitive to the climatic conditions. For example, in cold or wet conditions, the curing time is considerably extended.
With all the above materials the time needed before the repaired road is useable again is quite high This is to allow the bitumen to cool, the concrete to set or the epoxy resin to cure. This can be of great importance for example when repairing busy motorways or runways where a long period during which the road or runway is unusable and cannot be reopened to traffic is unacceptable.
U.S. Pat. No. 3,043,790 discloses a non-bituminous resin binder used in conjunction with cement powder in the presence of water such that the binder enhances the properties of a conventional aqueous cement mixture.
GB-A-1126296 discloses a resin binder including a petroleum hydro carbon resin, again used in conjunction with both water and cement, and again disclosing the conventional aqueous cement curing operation. The composition is disclosed as being useful in place of solutions, emulsions, mastics or hot melt adhesives, for attaching the petroleum resin, and optionally cement.
According to a first aspect of the present invention there is provided a method of providing a road repair material comprising the steps of:
producing pellets of thermoplastic resin material;
dry mixing the resin pellets with cement powder and at least one of sand, aggregate, polymer material and colorant; and
heating the mixed material until the resin softens.
A second aspect of the present invention provides a method of repairing a road surface comprising applying to a damaged portion of the road, the road repair material provided by the method of the first aspect
The resin preferably has a melting temperature of around 90-100° C. An example of such a resin is Escorez (TM) available from Exxon Chemicals of Fareham. The resin is preferably non-opaque, e.g. transparent or translucent.
The cement powder combines with the resin to provide improved strength over pure resin. The inclusion of cement also improves the absorbent properties of the material.
Hydrocarbon resin has a higher setting hardening temperature (around 50° C.) than bitumen, which means that once in place in the road, it will reach its setting temperature earlier than bitumen, allowing the repaired road to be used in a maximum of 2 hours.
The resin is preferably manufactured and processed into marble sized pellets or flakes (prills). Unlike bitumen these pellets or flakes are ‘dry’ i.e. they are not sticky and as such are easily mixed with other material without the need for heat. By providing the resin material as small pellets, it can be heated to its melting temperature much more quickly and so much less heat is required to raise it to the required temperature. In contrast, because bitumen is difficult to form into small pieces and is thus provided in blocks, a longer heating time is required and so more heat is required.
These pellets or flakes are then mixed with the other ingredients of the repair material, the resin acting as a binder for these additional materials. These other ingredients might include stone aggregate, wood chip and/or sand for filling, colorant, other polymer materials (e.g. ethylene vinyl acetate, E.V.A., available as POLYBILT 102 (TM) from Exxon Chemicals of Fareham or rubber powder e.g. Styrene-Isoprene-Styrene rubber available as SOLT 190 from Enichem Elastomers Of London), or oil (e.g. Edelex (TM) available from Shell Chemical Company of Manchester) for improving flexibility of the resin binder. Fibres may also be included to provide additional reinforcement. This loose mixture is put into sacks which are then sold by the manufacturer for use on site. The road repairer empties the sacks into a heating boiler when on site to cause the resin to soften allowing the ingredients to mixed together before being poured into the pot-hole or crack in the road.
As little or no heating is required during the preparation stage, as is the case with bitumen based repair material, the cost of manufacture is reduced. The reduced temperature to which the resin must be heated means less energy is needed on site which means less fuel is burned and less needs to be transported to site.
The resin mixture is preferably provided in consumable sacks or bags which will melt when heated to the temperature required to soften the resin. These bags are preferably made of low melt plastic so that they melt when placed in the heating boiler.
By using consumable bags, there is less waste on site and the mixture is easier to put into the heating boiler. All these factors lead to a considerable saving in cost as well as a reduction in waste.
Other elements may be added to the resin mixture to vary the characteristics of the resultant repair to ensure compatibility with the surrounding material. For examp
Addie Raymond W
Nixon & Vanderhye
RoadTechs Europe Limited
Will Thomas B.
LandOfFree
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