Process for preparing a bituminous ground covering

Details Process for preparing a bituminous ground covering Process for preparing a bituminous ground covering

1980-08-06

1983-05-10

Childs, Sadie L.

Stock material or miscellaneous articles

Web or sheet containing structurally defined element or...

Embodying intertwined or helical component

106281R, 427138, 427139, 427359, 428291, 428489, D03D 1300

Patent

active

043829880

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to a process for producing bituminous surfacing, wherein a solids mix is mixed with a bituminous binder in the flowable state, the mix formed is applied to the foundation, which is to be provided with the bituminous surfacing, and is then compacted. The invention also relates to bituminous surfacing produced by this process and to a hot plant mix for carrying out the process.
When producing bituminous surfacing, as is known, a solids mix is mixed with a bituminous binder. This mix is also called hot plant mix--as long as the binder is liquid in a manner of speaking. As a rule, the term "solids mix" is to be understood as a mixture of essentially different fractions of gravel and/or chippings and of screenings, whilst the term "bituminous binder" is to be understood as bitumen, tar or a mixture of these two.
As is known, such a binder has the property, at elevated temperature, of possessing a flowability which is comparable to that of a liquid and which decreases with falling temperature, but is never completely lost.
In producing bituminous surfacing, the hot plant mix mentioned above is supplied in situ or--as is more often the case--is delivered to the site in the hot state as a semi-finished product, as it were. On site, the hot plant mix is applied to the foundation (as a rule a gravel bed or a crushed stone bed) which is to be provided with bituminous surfacing, for example by means of a finishing machine, and is then compacted. Compacting is effected by exerting a pressure (for example by means of rollers) which forces the particles of the solids mix closer together and thus presses the bituminous binder into the interspaces which have remained free.
It is known that the surface of bituminous surfacing, which is subjected to loading again and again in one and the same area (for example along the tracks of vehicle wheels), is correspondingly deformed. This deformation is to be ascribed not only to wear but also to a plastic deformation of the surfacing, which deformation takes place only very slowly but sooner or later leads to fracture or crumbling of the bituminous surfacing, if the latter is not of sufficient depth.


SUMMARY OF THE INVENTION

The process according to the invention now makes it possible to obtain bituminous surfacing which is substantially tougher and/or more resistant to fracture.
The process is characterised in that metal fibres are admixed to the mix. Advantageously, these metal fibres are steel fibres of finite length. Accordingly, the resulting bituminous surfacing additionally contains metal fibres in the matrix which essentially contains the solids mix and the bituminous binder.
Admittedly, the use of metal fibres and also steel fibres of finite length for the reinforcement of concrete has already been disclosed, for example, in U.S. Pat. No. 3,429,094. In this case, however, the interaction between the cement (as the binder) and the steel fibres is fundamentally different. The adhesion of the cement to the individual fibre is comparable to a "microscopic positive connection" since, during the setting of the cement, the surface of the fibre is chemically attacked, that is to say roughened, and the still liquid cement slurry is attached to this roughened surface. After setting (which is an irreversible process) the cement has become a solid which adheres to the metal fibre for the reasons described above. During the compaction (by vibration) of the still flowable concrete mix, no pressure is exerted on the latter; merely, the air occlusions are expelled from the concrete mix in the manner of rising bubbles. The metal fibres present in the concrete mix thus undergo virtually no deformation; instead, they are merely wetted all round by the cement slurry and then remain anchored in the concrete in the random arrangement.
By contrast, the interaction of the metal fibres with the other components in the bituminous surfacing, proposed according to the invention, is different. On the one hand, the metal fibre in the bitumino

REFERENCES:
patent: 2355430 (1944-08-01), Flood
patent: 3291011 (1966-12-01), Defregger et al.
patent: 3429094 (1969-02-01), Romunldi
patent: 3650785 (1972-03-01), Ball et al.
patent: 4065591 (1977-12-01), Gannon

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