Cold Laid Bitumen Paving Material by Gilsonite

The use and preparation of paving mixtures of powdered asphalt in combination with liquid or partially liquid priming oils and mineral aggreate are well known. Various methods are used of incorporating priming oil and asphalt, the basis of which is the balancing out of quantities of priming oil to powdered asphalt, so that when the two combine by slow solution under pressure, it results in an asphalt binder of required consistency. This invariably requires at least of liquid priming oil and 50% of asphalt powder. If the priming oil is of very low viscosity, say below 590 seconds at 122 F. Furol, it is impossible to hold it in the mixture without running out before it has had a chance to thicken by the addition of the powdered asphalt. Where paving mixtures are required with a considerable lower consistency final binder than usual, the quantity of priming oil to powdered asphalt may be as high as which requires an extra high iscosity oil to be able to hold it on the stone. Where a high viscosity oil is used, a slight preheating of the aggregate is required to be able to effectively mix it with the oil or it requires the thickening of the oil by the introduction of a solid binder portion exclusive of the powered asphalt.

Gilsonite powder

The use of thin priming oils has been proposed where fines and/or sand are present but as the thin priming oil is a very rapid solvent for the powdered asphalt which is added, the mixture thickens almost immediately to a point where it cannot be stored, trans-shipped and laid. This process, therefore, requires a very vfine balance between the two products in regard to solvent power and very often results in mixtures that do not completely amalgamate as it is very diflicult to maintain a substantial coating of the thin priming oil on the crushed stone aggregate due to its tendency to flow.

An object of this invention is to provide a process of producing bituminous paving materials containing the required amounts of mineral aggregate, priming oil and asphalt which may be prepared in its entirety at one central plant.

Other objects of the invention are as follows:
To provide a process of producing asphaltic paving material which will allow mixing easily and will be mobile during spreading.
To provide a process of manufacturing bituminous paving materials in the cold, that is, at atmospheric temperatures.
Additional features of the invention will 'be apparent from thefollowing description:
Predetermined quantities of priming oil, powdered asphalt and mineral aggregate are taken. The priming oil is divided into two parts and one part of the priming oil is mixed with all of the mineral aggregate. After mixing thoroughly to wet all of the mineral aggregate, all of the powdered asphalt is added and the mixture is mixed further to uniformly incorporate the powdered asphalt in the priming oil coating the mineral aggregate. The remaining part of the priming oil is then added and the mixing continued until the priming oil is uniformly dispersed over the first coating of priming oil containing the powdered asphalt.

Alternatively the first part of the priming oil and powdered asphalt may be added at the same time to the mineral aggregate by spraying the oil and powder upon the surfaces of mineral aggregate being mixed in a mixer.

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