US2302644A - Road surface - Google Patents

Description

Nov. 17, 1942. g, E MAYY 2,302,644

ROAD SURFACE Filed Jan. 21, 1941 www INVE TOR.

odg Y Patented Nov. 17, 1942 paaren sraresearenr OFFICE ROAD SURFACE John Eric May, New York, N. Y.

Application January 21, 1941, Serial No. 375,296

2 Claims.

I'he present invention relates to road surfaces, as, for example, surfaces which are applied to a base of crushed stone, gravel, or similar base materials. It is known that of the surfaces heretofore used, asphalt has been considered superior to tar, because asphalt consists of a mixture of paraffin hydrocarbons which are relatively stable with respect to light, air and water, whereas, in the case of tar, the oils contained therein tend to evaporate, with the result of resinication and brittleness takes place.

It is the object of the present invention to provide a road surfacing, employing tar, which will overcome the defects of ordinary tar and tar compounds and which will be even superior to asphalt surfaces, without the cost thereof.

In the accompanying drawing:

Fig, 1 is a cross-section through a road showing the base layer comprising crushed stones or gravel and the tar layer spread over the base layer and comprising a top zone surface.

Fig. 2 is a cross-section through a road showing the condition of the tarred road shown in Fig. 1, after a coating of lime has been placed over the top tar Zone surface.

Fig. 3 illustrates the same road shown in Figs. 1 and 2 including the coating of lime as shown in Fig. 2, and the coating of water glass solution added thereto.

Fig. 4 illustrates the final stage of the road after a layer of slug dust and lime had been applied to the top tar Zone and bonded together rendering said tar top surface an asphalt-like character.

As an example of my road surfacing, a base of crushed stone, broken stone, gravel, crushed or broken concrete, or other suitable base, is preferably treated with applied tar so as to form an adhesive binder for the base material, sufficient tar being applied to form, when the tarred base is rolled, a fairly smooth surface. Prior to the rolling operation, or after merely a preliminary rolling, a layer of slag dust is applied to completely cover the tar. Preferably, the tar surface is rst dusted with lime, although the slag dust may be mixed with -20% of lime.

When the slag dust and lime covering is rolled down, it is sprayed with a 10-15% Water glass solution. By means of the water glass solution, the excess of lime is converted with the water glass into an insoluble calcium silicate, and any excess of water glass forms, through exposure to the air, gelatinous silicic acid.

It will thus be seen that the lime and water glass and their transformed products unite with the slag dust, closing up the pores thereof, and preventing the capillary rising of the component parts of the tar and therefore the disassociation of the tar into liquid and solid parts. On the other hand, the effect of light and air upon the tar is not Wholly barred, so that in consequence of the compression and suction elect of wheels rolling over the road, component parts of the tar are oxidized, condensed, and polymerized into stable, asphaltlike compounds.

The result of the process is to render the tar surface an asphalt-like character which will maintain its form. I am aware of the fact that it has been proposed to apply to the base coverings of roads, surfaces which are composed of mixtures of stone dust, slag dust, lime and limestone and water glass, with or without the addi tion of asphalt or pitch. Such surfaces have not. been successful, and the characteristic of the present invention is the separate application of the constituents specified herein in the consecutive order described, the result being that separate zones are formed, the tar Zone being the lowest, followed by the slag dust and lime Zone and followed by the nal surface of insoluble calcium silicate created through the combination of the water glass and lime and being present with silicic acid, so that the top surface is an acid zone.

The top surface has the effect of rejecting Water so that decomposition through freezing is avoided, a result which so far has not been obtainable with tar surfaces. Moreover, the usual dark color of macadam and tar roads is avoided, the surfaces having the appearance of asphalt treated with dry cement, or the like.

Tests of roads built in accordance with the present invention has demonstrated resistance to wear even superior to asphalt surfaces, that the surface is non-hygroscopic, that the appearance of the road is that of an asphalt road, that the road is more resistant to softening through direct sun rays and heat than the average asphalt road, and that the road is therefore Well adapted to tropical conditions, and this with a cost very substantially less than in the case of asphalt constructions.

While in the above specification, I have referred to road surfaces, it will be understood that the invention is adapted to such surfaces as oors of buildings, the surfaces of tennis courts, etc.

Having described my invention, What I claim and desire to secure by Letters Patent is as follows:

1. In a method for surfacing roads including a layer of tar applied to a base to form a covering lime applied to said tar zone and bonded thereby, the layer being suicient to completely cover the tar Zone and the lime being about 1020% of the layer, an outer coating of insoluble calcium silicate and gelatinous silicate acid formed by the reaction of water glass with said lime and the decomposition of said Water glass by oxidation,

`said calcium silicate and silicate acid rendering said tar top surface an asphalt-like character.

JOHN ERIC MAY.

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