Powdery hydrophobic filler for bituminized traffic surfaces

Details Powdery hydrophobic filler for bituminized traffic surfaces Powdery hydrophobic filler for bituminized traffic surfaces

1994-05-04

1995-09-26

Bell, Mark L.

Compositions

Frost-preventing, ice-thawing, thermostatic, thermophoric,...

252 71, 106461, 106466, 106482, 106788, E01C 900

Patent

active

054532124

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

This invention relates to a powdery hydrophobic filler, based on at least one substance which lowers the freezing point of water, for bitumen-bonded traffic surfaces.


STATEMENT OF RELATED ART

It is known that road surfaces containing substances which reduce the freezing point of water can be prepared in order to prevent ice from forming, particularly at ambient temperatures varying around 0.degree. C., and to facilitate snow clearing operations. For example, DE-OS 24 26 200 describes a bituminous or asphalt-containing preparation for the production of a road surface that inhibits ice formation and melts snow, containing alkaline earth metal halide and alkali metal hydroxide particles incorporated in the structure of the mineral and protected by a water-tight coating of a drying oil or a plastic from the group consisting of polyvinyl acetate, polyvinyl alcohol, epoxy resin or acrylic resin. The thawing effect of these particles, which have a particle size of up to 7 mm, is brought into action after destruction of the oil or plastic coating by the usual abrasion of the road surface by traffic. However, this known preparation has the major disadvantage that the relatively large particles are difficult to disperse uniformly in the other constituents of the road surface, so that the thawing effect obtained is not uniform over the entire area of the road surface. In addition holes in the road surface can be formed by the dissolving out of these large particles and have to be subsequently repaired.
EP 153 269 describes the use, for road surfaces, of a fine particle mixture, with a particle size below 0.2 mm, which, in addition to sodium chloride, contains polyurethane, perlite and optionally carbon black as a hydrophobicizing component. In the fine particle mixture, the percentage content of the hydrophobicizing component is between 5 and 75% by weight of the percentage content of the hydrophilic components.
It is desirable to keep the percentage filler content based on a substance which reduces the freezing point of water in an asphalt mixture relatively low because, on the one hand, minimum quantities of other fillers which do not reduce the freezing point of water, for example mineral powder, are often required although, on the other hand, the permitted total quantity of filler is limited by the particular technical specification. Accordingly, there is an interest in highly effective fillers based on a substance which reduces the freezing point of water. This means that the percentage content of substances reducing the freezing point of water in fillers such as these should be as high as possible. The higher the percentage content of substances which reduce the freezing point of water (hydrophilic substances), the lower the percentage availability of substances which hydrophobicize the hydrophilic substances. However, for the absolutely essential long-term effect of a filler incorporated in a traffic surface, premature leaching of the substances which reduce the freezing point of water must be avoided, i.e. a low extraction rate has to be guaranteed by particularly good hydrophobicization. In addition, such fillers should be stable even at temperatures above 250.degree. C. so that they may readily be incorporated, for example, in bituminous mastic concrete.


DESCRIPTION OF THE INVENTION



Object of the Invention

Accordingly, the problem addressed by the present invention was to provide a filler for bitumen-bonded traffic surfaces which, even in small quantities, would enable such traffic surfaces to be protected much more effectively against freezing over, even in the long term, by comparison with known fillers.


SUMMARY OF THE INVENTION

It has been found that the stringent requirements which a filler of the type in question is expected to meet are satisfied by a powder-form filler based on at least one substance which reduces the freezing point of water and which contains hydrophobicized amorphous silicon dioxide in quantities of 0.1 to 10% by weight.
Accordingly, the present i

REFERENCES:
patent: 5106520 (1992-04-01), Salyer

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