US2086968A - Bituminous composition for coating mineral aggregate - Google Patents

Description

Patented July 13, 1937 PATENT QFFICEE BITUMINOUS C'OMPGSITEON FOR COATING MINERAL AGGREGATE Hiram M. Stafford, Chicago, Ill., assignor, by mesne assignments, to Sealdrok Company of New England, a corporation of Massachusetts No Drawing.

Application June 28, 1935 Serial No. 28,923

2 filaims.

My invention relates to a bituminous composition for waterproofing mineral aggregate in the preparation of material for road building, street paving, miscellaneous surfacing, and various 5 other construction purposes.

My improved composition is primarily intended for use in connection with the method and apparatus for conditioning mineral aggregate and the product formed thereby, as disclosed in :19 my United States Letters Patent No. 2,041,155,

dated May 9, 1936. Briefly, the method contemplates the conditioning of the mineral aggregate at the quarry, or other source of supply, by first heating the aggregate pieces to expel the contained moisture and a portion of the air in the locked inthe interstices of the pieces and at the same time provides a thin bituminous covering on the external surfaces. The coating is sufficiently thin to prevent any coalescing of the pieces together into an agglomerated form when stock piled for an appreciable length of time, but is capable of fusing and merging with a subsequently added bituminous coating in the making of roadway material, so that the finished coat is substantially uniform in consistency and L) keyed and interlocked in the pores of the individual pieces.

It is, therefore, the principal object of my invention to devise a bituminous waterproofing 4 composition for use in connection with the foregoing method and which is characterized by sufficient penetrability to partially or completely impregnate the aggregate pieces and by a sufficient body to cover the pieces with a thin bituminous coating that extends into and is interlocked in the interstices of the pieces for hermetically sealing the pieces against subsequent moisture absorption.

A further object is to provide a composition 5 having the foregoing characteristics and which additionally insures a better adhesion with a finish coating of bituminous material in the preparation of a complete paving material, than is now obtained in the industry.-

A further object is to provide a bituminous composition for the purpose indicated, which is capable of being applied at atmospheric temperature and which includes ingredients adapted to somewhat retard the setting of the material when first applied by maintaining its fluidity for a time sufficient to insure the penetration of the coating into the interstices of the individual aggregate pieces and the subsequent interlocking of the coat therewith.

These and further objects of my invention will be set forth in the following specification and the novel means by which said objects are effectuated will be definitely pointed out in the claims.

In the preparation of my improved composition, I use an asphalt cement having a penetration of 200 to 300 at 77 degrees F., according to the standard established by the. American Society for Testing Materials. As solvents for the asphalt, I employ petroleum naphtha having a specific gravity of from 50 degrees to 60 degrees Baum and a commercial grade of kerosene having a specific gravity of approximately degrees Baum. I also prefer to use a third solvent naphtha commonly known as "tar naphtha. This particular naphtha has a greater wetting power than the other solvents heretofore noted, 1 and increases the capacity of the composition to spread over the aggregate pieces and penetrate into the interstices thereof.

o The foregoing ingredients are mixed at atmospheric temperature and in the proportion of 40 to 65 per cent of asphalt, 30 to 55 per cent of petroleum naphtha, 5 to 15 per cent of kero sene, and, when used, 4 to 10 per cent of tar naphtha. The specific composition which does not include the tar naphtha and which has been found highly suitable comprises per cent of asphalt, 40 per cent of petroleum naphtha, and 10 per cent of kerosene. Where the tar naphtha is employed, a typical composition would comprise 50 per cent of asphalt, 30 per cent of petroleum naphtha, 10 per cent of kerosene and 10 per cent of tar naphtha. In general, the higher asphalt content would be used with the softer stones, such as limestone, while the lower asphalt content would be used with the harder stones, such as trap rock or granite.

This composition can be stored indefinitely in suitable containers and transported and applied cold or at atmospheric temperature. The viscos- V ity of the composition is sufficiently low to permit its application to the aggregate pieces by sprayl ing, or other modes of application can be used, suchas dipping and the like. When applied, the

naphtha ingredient tends to evaporate rather rapidly, but this evaporation rate is restrained to some extent by the kerosene ingredient, so that the composition is given an adequate opportunity to thoroughly seep into the pores of the aggregate pieces. Accordingly, when the volatile ingredients have finally evaporated, each aggregate piece is fully coated with a thin bituminous covering which extends into and is interlocked in the pores of each piece, the coating being slightly sticky or gummy to the touch and completely waterproofing and hermetically sealing the aggregate pieces against the subsequent reabsorption of moisture. It will be understood that, and as hereinbefore indicated, this composition is intended for application to aggregate pieces under the conditions set forth in the aforesaid copending application, the temperature of the composition being less than that of the aggregate pieces and the temperature of the latter being insuflicient to cause substantial evaporation of the volatile ingredients of the composition.

Aggregate which is coated with my improved compound may be stored indefinitely in stock piles with an assurance that the individual. pieces will not reabsorb moisture. This absorption is a fruitful source of damage in finished paving due to freezing of the moisture during the winter months and the resultant peeling of the coating from the pieces of the aggregate, thus destroying their bond with other pieces. This condition is completely prevented by the use of my compound when applied as before indicated, because the moisture is expelled from the stone pieces before the application of the compound and. the coating formed thereby completely prevents subsequent reabsorption. The thinness of the coating prevents any coalescing of the pieces when stock piled, which would otherwise result in agglomerated masses that would require breaking before being treated with a finished coat of a paving material, such as asphalt and the like. However, the coating is of such a nature that it fuses and merges readily with a subsequent finish coat of bituminous material and, when so coated, the finished covering is substantially uniform in consistency and is keyed and interlocked in the pores of the individual aggregate pieces. Because of this capacity of my compound for providing adhesion with a finish coat, the use of liquefiers as commonly employed in making coldlay', asphalt, paving mixture is completely eliminated. Such liquefiers are a positive detriment inasmuch as they leave a greasy surface on the aggregate pieces and do not provide an effective bond with the finish asphalt coating.

I claim:

1. A waterproofing bituminous composition for coating mineral aggregate with a covering adapted to bond with a finish coat of bitumen and comprising 40 to 65 per cent of asphalt, 30 to 55 per cent of petroleum naphtha, 5 to 15 per cent of kerosene, and to 10 per cent of tar naphtha.

2. A waterproofing bituminous composition for coating mineral aggregate with a covering adapted to bond with a finish coat of bitumen and comprising per cent of asphalt having a penetration of from 200 to 300 at 77 degrees 30 per cent of petroleum naphtha, 10 per cent of kerosene, and 10 per cent of tar naphtha.

HIRAM M. STAFFORD.

Patent N0. 2,086,968.

HIBAM M. STAFFORD.

It is hereby certified, that the above numbered patent was erreneeely iseued. to "Seeldrelt Gonzpeny e1? Kiev; England, e corporation of setts" as assignee by mesne aesignmente, Whereas said; patent sheuld. have been issued to the inventor, Hiram Stafford, as shown by reeerde "n office; and that the eaicl Letters Patent elzeuld be of assignments iread with this correctien therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 21st day of September, A. D. 1957.

(Sea-x1) Acting Cemmissioner of Patents" Henry Van Arsdale