GB2373277A

GB2373277A - Method of producing load bearing road surface

Info

Publication number: GB2373277A
Application number: GB0105154A
Authority: GB
Inventors: Robert Hoare
Original assignee: Civil & Ind Products Ltd
Current assignee: Civil & Ind Products Ltd
Priority date: 2001-03-02
Filing date: 2001-03-02
Publication date: 2002-09-18
Anticipated expiration: 2021-03-02
Also published as: GB0105154D0; GB2373277B

Abstract

The method, particularly for use repairing and resurfacing roads formed from concrete, comprises laying a first layer 6 of an open graded asphalt topping with a void ratio of between 20% and 30% flooded with microsilica mortars and subsequently laying a second layer 8 of a wearing course on top of the first layer. The wearing course preferably comprises a layer of a bituminous material. Also claimed is a method of repairing a concrete highway and a road comprising a flexible or semi flexible membrane and a second layer of a wearing material.

Description

Improved Road Surfacing The present invention relates to improvements in and relating to a method of construction of a road surface and a road surface produced according to the method.

It is known to construct roads and other highways from a series of courses topped by a road surface.

It is known to provide road surfaces in the form of bituminous road surfacing materials. It is a problem with such surfacing materials that they may move, or become rolled or otherwise deformed under the action of continuous heavy goods vehicle traffic. Such vehicles can be of the order of 48 tonnes. Such wear produces a rutting effect, known as tramlines, in road surfaces. The effect is particularly pronounced on major motorways and trunk roads in particular on those roads which take the largest amount of heavy goods vehicle traffic.

On the approach to traffic lights or roundabouts a further effect may result. Due to the uneven braking of the front wheels, the vehicles tend to pitch forward and back causing a sinusoidal undulation of the road surface to be added to the tramline effect.

Tramlines and sinusoidal undulations occur because the load bearing characteristics of conventional wearing courses, that is bituminous materials combined with various aggregates, are not strong enough to stand the loads that are being put on them. In particular, they do not spread a load from a passing vehicle, such as a heavy goods vehicle, onto the lower road construction courses.

These wearing effects are undesirable for a number of reasons. Tramlines or ruts act as drainage points and may fill with standing water. This is a motoring hazard since cars and other lights vehicles will aquaplane in the water. In other words, a vehicle tyre will be unable to displace the standing water and the tyre loses contact with the road surface. This clearly

adversely affects the braking ability of the vehicle.

Further, should the standing water become frozen, damage may be caused to the road surfacing materials which ultimately will lead to repair of the road surface being required.

Roads and other highways constructed using concrete, either reinforced or without internal reinforcement, are difficult to repair. At present such roads are either ripped up, which is a difficult process because the concrete is very hard, or a layer is plained off the top surface and a layer of a conventional wearing course added to return the road surface to a required level. The problem with simply adding a bituminous wearing course is that this too may deform to form tramlines or rutting on top of the remaining concrete in the manner described above.

It is an advantage of the present invention that it substantially reduces or eliminates these problems.

According to a first aspect of the present invention a road comprises at least a first layer and a second layer, the first layer comprising a flexible or semi flexible membrane and the second layer comprising a wearing course.

The use of the flexible or semi flexible membrane extends the load bearing platform thereby reducing the tendency of the wearing course to deform under load.

According to a second aspect of the present invention a method of producing an improved load bearing road surface comprises laying a first layer of an open graded asphalt topping with a void ratio of between 20 and 30% flooded with microsilica mortars and subsequently laying a second layer of a wearing course on top of the first layer.

Preferably, the flexible or semi flexible membrane comprises an open graded asphalt topping with a void ratio of between 20 and 30% flooded with microsilica mortars.

Preferably, the wearing course comprises a layer of bituminous material.

According to a third aspect of the present invention a method of repairing a concrete highway comprises the steps of removing a top surface of the concrete highway, cracking and seating the highway, laying a first layer of a flexible or semi flexible membrane and then laying a second layer of a wearing course on top of the first layer.

It is an advantage that this produces an enhanced surface with better wear and grip characteristics than the original concrete.

The invention will now be described, by way of example only, with reference to the accompanying Figure which shows a section through a roadway constructed in accordance with the present invention.

Referring to the Figure, there may be seen a roadway construction comprising a pre-existing road layer 4, for example a number of courses or a concrete highway having a top layer stripped off, a first layer of a flexible or semi flexible membrane comprising an open graded asphalt topping 6 with a void ratio of between 20 and 30% flooded with microsilica mortars and a second layer comprising a wearing course 8 of bituminous material.

The asphalt topping may incorporate cementitious mortar. Preferably the mortar is of a special kind incorporating microsilica particles which are very small sized particles of silica (up to one hundred times smaller than the associated cement particles) which ensures a higher packing density of the mortar. In particular such mortar comprises Portland cement, microsilica, superplasticiser and fine quartz sand. Of these components the microsilica may be amorphous silicon dioxide produced as a product of filtered smoke condensation from the production of ferrosilicium and is in the from of very small spherical particles. The superplasticiser may be sodium polydiniaphtenemethanesulphonate. The microsilica particles replace most of the conventional sand used in mortar mixes and the microsilica particles are of a mean diameter of around 0.1 micrometer and of spherical shape. The microsilica particles which react with calcium dioxide in the cement and provides a

microstructure which is very dense and becomes denser in the hydration phase. Alternatively a polymer cement mortar may be used. A suitable open graded asphalt topping 6 of the kind noted above is available under the brand name DENSIPHALT by DENSIT A/S.

In a known construction, an 80 mm layer of a conventional wearing course, such as a bituminous material, overlies a lower road construction. A point load on the surface of the wearing course will be distributed over a 76 square millimetre area on top of the underlying road construction (illustrated by cone 2 on the Figure).

In an embodiment in accordance with the illustrated embodiment, an 80 mm layer of open graded asphalt topping 6 of the kind noted above is interposed between the lower road construction 4 and an 80 mm thick layer of a wearing course 8. This construction extends the load platform on the underlying road construction 4 to 174 square millimetres (illustrated by cone 10 in the Figure).

It will be understood that the exact thickness of each of the layers of the wearing course 8 and the open graded asphalt 6 of the kind noted above can be adjusted to suit the anticipated load requirements of the road or highway under construction.

It can further be seen that the wearing course 8 can be constructed of a material to give the required friction and/or drainage characteristics, since the open graded asphalt 6 of the kind noted above is principally responsible for the load characteristics.

While the laying of two layers is more time consuming and costly than the laying of a single layer, the enhanced life of the road or highway produces a saving in terms of lower repair and maintenance costs.

Since a wearing course 8 having desired friction characteristics may be used, and the road or highway is less prone to tramlining or rutting, a road or highway constructed in accordance with the present invention has improved safety features.

Claims

CLAIMS 1 A method of producing an improved load bearing road surface comprises laying a first layer of an open graded asphalt topping with a void ratio of between 20 and 30% flooded with microsilica mortars and subsequently laying a second layer of a wearing course on top of the first layer.
2 A method of repairing a concrete highway comprising the steps of removing a top surface of the concrete highway, cracking and seating the highway, laying a first layer of a flexible or semi flexible membrane and then laying a second layer of a wearing course on top of the first layer.
3 A method according to claim 1 or claim 2, in which the flexible or semi flexible membrane comprises an open graded asphalt topping with a void ratio of between 20 and 30% flooded with microsilica mortars.
4 A method according to any previous claim, in which the wearing course comprises a layer of bituminous material.
5 A method of producing an improved load bearing road surface or of repairing a concrete highway substantially as described herein with reference to and illustrated in the accompanying drawing.
6 A road comprising at least a first layer and a second layer, the first layer comprising a flexible or semi flexible membrane and the second layer comprising a wearing course.
7 A road according to claim 6, in which in which the flexible or semi flexible membrane comprises an open graded asphalt topping with a void ratio of between 20 and 30% flooded with microsilica mortars.
8 A road according to claim 6 or claim 7, in which the wearing course comprises a layer of bituminous material.
9 A road substantially as described herein with reference to and illustrated in the accompanying drawing.