Patent Application
20080008828
The present invention is a method of sealing and strengthening the joints in an asphalt road surface and subsurface to prolong the useful life of the road. The sealing method utilizes a polymer modified cationic maltene emulsion containing polymer modified maltene oils and resins, surfactants, and wetting agents.
The emulsion is applied to the longitudinal joints in the asphalt surface. When an asphalt road is constructed, the area around the center longitudinal joint or joints is difficult to properly compact. The joint itself, and a surrounding band approximately a foot wide on either side of the joint, cannot be compacted as thoroughly as the main body of the asphalt pavement. The asphalt pavement in the joint area is more porous than the other areas of the asphalt pavement, and is therefore more susceptible to water permeation, oxidation, and tension force damage.
The emulsion is typically sprayed onto the road surface. A spray bar two to three feet wide and two to three inches in diameter, with one-eighth inch nozzles is used in the preferred embodiment to spray the emulsion onto the road surface. The application rate is controlled by a computerized flow manager, which allows the emulsion to be precisely applied to the joint area of the road surface. Once the flow rate computer has been set to the desired application rate, the application of the emulsion is very accurate due to the computer control of the flow, regardless of travel speed variations of the sprayer.
While the preferred embodiment of the invention uses an automated sprayer to apply the emulsion, any means suitable for application of a liquid emulsion could be effectively used provided the required accuracy of application is maintained.
After it has been applied to the asphalt pavement, the emulsion of the present invention reduces the voids in the asphalt pavement, both on the top surface and beneath the surface. The emulsion alters the modulus of elasticity of the binders in the asphalt pavement mixture, strengthening the asphalt binders and introducing rubber-like properties to the surface and below the surface throughout the joint area and the bordering band where the emulsion is applied. The increased elasticity of the asphalt pavement increases its resistance to tension forces. The application of the emulsion also reduce the water absorption of the asphalt pavement. These two factors, tension damage and water permeation, are the chief components of premature asphalt surface damage.
The emulsion is formed from selected oils and resins extracted from a crude oil source, with a rubber component added after the emulsion has been prepared. The base oil of the emulsion is a petroleum resin. In the preferred embodiment, Petroleum Resin C.A.S. 64742-04-7 or 64742-11-6 is chosen. The base resin is mixed with water, emulsifiers, and a polymer compound. In the preferred embodiment the polymer compound is Surfonic NP-95 or Witcolnol NP-100, and the emulsifier is E-11 Redicote or AA-57. The emulsion comprises, as a percentage by weight, 58%-60% petroleum resin, 36.75% water, 3% polymer compound, and 2.25% emulsifier.
The emulsion is prepared so as to minimize the particle size in order to give the emulsion maximum penetrating capability. The components are mixed in a colloid mill that provides for a particle size setting of 0.018-0.025. However, milling alone will not provide optimal preparation of the emulsion. The base oil is heated to 200°-208° F. to increase the volume. The water is heated to 100°-120° F. When the mixture is cooled to ambient temperature, the particle size of the emulsion is reduced. In order to give the emulsion more rubber-like properties, rubber in the amount of 2% by volume is added to the emulsion. The rubber chosen for the preferred embodiment is styrene butadiene polymer, or unvulcanized synthetic virgin rubber.
The process of the present invention has shown excellent performance in field testing. In a first test application, the emulsion of the present invention was applied to alternating sections of a new construction asphalt road surface. The untreated sections of the road surface served as control areas. The emulsion was applied to 300 foot long sections two feet wide centered on the longitudinal joint. The application rate was 0.10 gallons per square yard. After three years, visual inspection was made of the test surface. Photographic records show marked differences in the condition of the surface. Those areas adjacent to the joints that were treated with the emulsion equaled or exceeded the performance of the highly compacted areas of the road surface away from the longitudinal joint. Those areas adjacent the joint that were not treated with the emulsion showed significant deterioration that required repair or replacement.
The above disclosure is not intended as limiting. Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the restrictions of the appended claims.
