Such a draining structure is highly advantageous in respect of traffic safety. Problems of pools of water on the road surface, aquaplaning and the like are essentially prevented with such a structure. The drawback of such road surfaces is that they tend to become fouled with sand and seeds blown therein which in some conditions can even result in plant growth in the large pores.

It is an object of the invention to provide a method not having said drawback and displaying a number of advantages as specified hereinbelow.

In respect of the above, the invention provides a method for improving a road surface with large pores, for instance comprising a top layer of large-pore asphalt, according to which method a mixture is formed of ground material consisting substantially of grains of considerably smaller dimensions than those of the large pores of the road surface, such as sand, and an at least slightly fluid curable plastic, for instance a two-component mass; wherein the quantity of plastic is chosen such that in cured state the plastic mutually adheres the grains in the region of their contact surfaces while preserving the porosity of the cured mixture;

the mixture is then distributed over the road surface prior to curing such that the mixture penetrates at least to a certain depth into the large pores thereof; the mixture is finally allowed to cure to a relatively fine-pore solid mass.

By filling the large pores with a relatively fine- pore material the draining or water-discharging character of the road surface is not disrupted, while fouling and collecting of seeds are effectively prevented.

The mixture is applied in a ratio such that relatively little plastic is used as adhesive, such that there is no danger of the fine-pore structure being closed, but sufficient to ensure that the grains effectively adhere to each other. A ratio of ground material : plastic can be envisaged in the order of for instance 96%: 4% (% by weight).

A specific embodiment has the special feature that a non-cured plastic is used which displaces moisture which may be present in the ground material such that the plastic can adhere directly to the grains without being impeded by moisture.

Such an embodiment has the advantage that work for the purpose of performing the method according to the invention can also be carried out effectively in moist conditions or even wet conditions.

In certain conditions it may be advantageous for a mixture to be applied such that it forms a relatively fine-pore cover layer on the original road surface. This method can be performed in one operation by applying an excess of mixture. It is also possible to first provide at least the uppermost zone of the road surface with the mixtures and only then, for instance after partial or full curing thereof, to apply the cover layer.

A specific embodiment is formed by a variant in which at least one additive is added to the mixture or the constituent components.

A specific embodiment hereof has the feature that the additive is a colouring agent. For laying of for instance cycle paths a different colour can be applied than for traffic lanes intended for automobiles.

Yet another embodiment has the special feature that the additive is a flexibilizing substance, for instance comprises rubber granules. Such an embodiment is particularly suitable for use in the situation where the ground surface allows some undesired movement, for instance soft ground which tends to be compacted under the influence of passing traffic. The plastic can itself be of a type which possesses a certain flexibility in the cured state.

The method according to the invention is preferably embodied such that the plastic is of the type that has a good adhesion to the material of the road surface, for instance bitumen and/or gravel.

Reference is finally made to the optional possibility of embodying the method according to the invention such that the plastic is of the type that has a good adhesion to the material of the road surface, for instance bitumen and/or gravel.

An advantageous embodiment has the feature that curing of the plastic is accelerated by temporarily increasing the temperature. The method can hereby be carried out more rapidly.

The non-cured mixture can be applied to the road surface by hand or mechanically. To enhance rapid penetration into the road surface, it is possible to cause the mixture to penetrate into the large pores as rapidly as possible by means of a sweeping process, for instance by means of a broom.

In a mechanical embodiment, for instance by means of a vehicle, the method can take place fully

automatically by picking up ground material at the front of the vehicle, mixing it with the fluid plastic in a suitable mixing device which is carried by the vehicle and depositing it in metered manner at the rear. The brushing process can herein also take place, optionally in combination with a rolling process and/or heating.

Finally, the invention relates to a road surface obtained by applying the method as according to the above stated specifications, which road surface has a structure with large pores, comprising for instance a top layer of large-pore asphalt, which pores are filled to at least a certain depth with a relatively fine-pore solid mass which consists of ground material substantially consisting of grains of considerably smaller dimensions than those of the large pores of the road surface, which grains are mutually adhered by a cured plastic.

A road surface improved in accordance with the method according to the invention has the following advantages: -Sound reduction Due to the open construction and the very fine filter action in the pores of the filler, the sound produced by a tyre will pass through the filter, the sound will again be reflected upward in the open construction but is herein damped by the above filter. A considerable reduction in sound will hereby occur (minimum 3 dB (A)).

-Decrease in the fouling in the hollow space of the construction.

The fine structure of the filler reduces fouling and functions here as filter or sieve for sand and organic contamination.

-Increase in lifespan.

In draining asphalt constructions such as Very Porous Asphalt (ZOAB) stone loss (fraying) occurs

after a number of years; the filler. will prevent this (fraying).

Water-permeability.

The water-draining capacity of the draining construction is ensured by the high hollow-space content of the filler.

Improvement in combatting icy conditions.

The road surface becomes a flat whole due to the filler, whereby salt for combatting icy conditions does not enter the pores as in the case of present draining constructions but remains lying on the surface.

Initial frictional resistance.

Bitumen, the adhesive for mutual adhesion and encapsulation of the mineral aggregate, has the property that it melts on an increase in temperature (such when a vehicle brakes); the viscosity of the bitumen increases. This has the result that the braking distance of a vehicle on a new road surface is considerably longer than on an older road surface.

Owing to the filler the macro-texture of the surface changes, the tyre has more contact area.

The plastic coating will also cover the top layer of the bitumen whereby this layer also becomes harder.