Compositions: coating or plastic – Coating or plastic compositions – Bituminous material or tarry residue
Patent
1987-06-15
1989-01-31
Lieberman, Paul
Compositions: coating or plastic
Coating or plastic compositions
Bituminous material or tarry residue
106DIG7, 106269, 1062811, 208 44, C08L 9500, C10C 302
Patent
active
048013323
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates generally to paving compositions and more particularly to an improved asphalt cement paving composition and method for its formation.
BACKGROUND ART
Asphalts combined with aggregates have been employed as paving compositions for many years. Asphalts generally include bitumens as a predominant constituent and are conventionally obtained as a solid residue from the distillation of crude petroleum. In forming paving compositions, asphalts must be converted to a fluid state.
One fluid form of asphalt is the suspension or emulsion of asphalt in water. After spreading and compressing aggregate/asphalt emulsion paving compositions, the water evaporates and the asphalt hardens into a continuous mass. Another fluid form of asphalt employed in paving is a cutback, i.e., a fluid petroleum product produced by fluxing an asphaltic base with a suitable organic solvent or distillate. Pavements are formed by spreading aggregate/cutback paving compositions and evaporating the volatile distillate from the mass.
An advantage of forming pavements with asphalt emulsions and cutbacks is the avoidance of high temperature application. In the most common paving technique, the asphalt and aggregate are mixed and applied at elevated temperatures in order to maintain the asphalt in a fluid state in forming the pavement. This asphalt, which is neither cutback nor emulsified, is referred to as an asphalt cement.
A major problem with cutbacks and emulsions is their low adhesivity to aggregate in comparison to asphalt cement. This is due primarily to the presence on the aggregate surface of (a) the organic solvent or oil in the cutback and (b) the water in the emulsion which interfere with the formation of an adhesive bond between the aggregate and the asphalt.
One technique which has been disclosed to increase the adhesivity of emulsions and cutbacks is set forth in U.S. Pat. No. 3,243,311. There, the aggregate is pretreated with one of a variety of metal compounds stated to be cross-linking agents for the organic binder to oxidize, polymerize or catalyze and thereby harden the binder. The pretreatment is supposed to improve adhesivity of the binder and aggregate, specifically for clay-type soil aggregates. The cross-linking agents are stated to be multioxidation state metals in their higher oxidation state, with the anions including a large variety of organic and inorganic acids. In addition, salts such as the halides and a large variety of inorganic oxides are mentioned. The cations disclosed include Group I, Group IV, Group V, Group VII, and Group VIII metals as well as rare earth metals. Specific examples include Cu(OH).sub.2, CuCl.sub.2, FeCl.sub.3, CuSO.sub.4 and KMnO.sub.4. In each instance, the soil is pretreated with the cross-linking agent prior to mixing with the asphalt.
In U.S. Pat. No. 1,328,310, an asphaltic pavement is disclosed in which copper sulfate is added to the asphalt for improving physical properties. Other compounds mentioned for this purpose include the sulfates or selenates of aluminum, chromium, iron, indium, gallium, and the sulfates or selenides of sodium, potassium, rubidium, ammonium, silver, gold, platinum or thallium. These compounds are relatively insoluble in the asphalt.
In U.S. Pat. No. 2,773,777, a bituminous composition particularly suitable for airport runways exposed to the high temperatures of the exhaust gases of jet engines is disclosed. The composition includes bitumen emulsion, portland cement, and mineral aggregate. To this mixture is added an aqueous solution of one of a number of water soluble salts for the purpose of giving plasticity to the composition. The salts disclosed are water-soluble polyvalent metal salts of a strong mineral acid, especially sulfuric, hydrochloric and/or phosphoric acids. The most effective salts are stated to be alkali earth metal salts including calcium chloride, magnesium chloride, barium chloride and the like. Salts of amphoteric metals are also taught to be useful, including aluminum sulfate, chromium chlo
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Clancey Patrick K.
Leonard, Jr. John B.
Selfridge Philip T.
Chemcrete International Corp.
Kirschner Helene
Lieberman Paul
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