US1964987A

US1964987A - Process of constructing bituminous macadam roads

Info

Publication number: US1964987A
Application number: US592194A
Authority: US
Inventors: Raymond B Harris
Original assignee: WOOD CHEMICAL PRODUCTS Co
Current assignee: WOOD CHEMICAL PRODUCTS Co
Priority date: 1932-02-10
Filing date: 1932-02-10
Publication date: 1934-07-03
Anticipated expiration: 1951-07-03

Description

Patented July 3, 1934 UNITED STATES PATENT OFFICE PROCESS OF CONSTRUCTING BITUMINOUS MACADAM ROADS No Drawing. Application February 10, 1932, Serial No. 592,194

3 Claims.

This invention relates to the process of constructing roads by means of wood tar and has for its object to render the process more expeditious, cheaper, and safer.

5 In the construction of roads and highways of the bituminous macadam type a base several inches thick of lime rock or oyster shells or a combination of both, is prepared and thoroughly rolled. This base is allowed to season and consolidate and becomes a solid monolith through the action of the materials entering into its construction. It is, however, susceptible to the action of water and has a soft Wearing surface.

The present practice is to place a priming coat of coal tar over the base, then a layer of petroleum asphalt and finally a covering of crushed granite in order to exclude water and provide a hard Wearing surface. It is essential that the asphalt top and the base be firmly bound together and it has been found from experience that petroleum products are not satisfactory for the purpose.

I have found that the use of a priming coat of wood tar sometimes called pitch of wood or its derivative wood tar oil, or a priming coat composed of wood tar or wood tar oil and petroleum products in the construction of a road of the bituminous macadam type, as a binder between the base and the asphalt top coat produces a road which is very durable and such priming coat binds the asphalt top coat to the base of the road in a satisfactory and relatively permanent manner. Such priming coat penetrates the base much deeper than a petroleum priming coat and adheres 5 more firmly to the asphalt top coat. It can be applied when the base is wet, is not corrosive or injurious to the workman and because of the rapidity of the penetration, permits the road to be used more quickly. If a combination of wood tar or wood tar oil and petroleum products is used, the proportions can be varied to suit the construction of the base and the materials used in the base and the top coat. As an example I have found that a mixture of sixty parts of wood tar or wood tar oil and forty parts of petroleum fuel oil of high specific gravity makes an excellent priming coat over a lime rock base.

I claim:

1. A macadam road construction comprising essentially a base aggregate which is predominantly alkaline in character and an asphalt wearing surface, and an intermediate priming layer comprising one of the group consisting of wood tar and wood tar oil, said intermediate layer being highly penetrative of said base aggregative and distinctly acid in reaction, whereby secure adhesion between said base aggregate and the said intermediate priming layer, as well as between the latter and said wearing surface, is assured.

2. The construction defined in claim 1, wherein said base aggregate consists essentially of one of the group comprising lime rock, oyster shells, and an admixture of lime rock and oyster shells.

3. The construction set forth in claim 1, wherein said priming layer consists of a mixture of about sixty parts of a wood tar constituent and about forty parts of petroleum fuel oil of high specific gravity.

RAYMOND B. HARRIS.