GB2105391A - Preparing a concrete layer on asphalt - Google Patents

Abstract

The method consists in milling the asphalt so as to obtain a rough surface and casting a thin layer of a concrete which contains fibres or is reinforced in some other way and that the concrete is both rammed and vibrated. To this purpose a vibrator beam may be used which is suitable for both ramming and vibration.

Description

SPECIFICATION Preparing a concrete layer on asphalt This invention relates to a method of preparing a thin concrete layer, constituting an attrition layer, on asphalt.

Danish Patent Specification 139 1 64 describes a method of casting a concrete slab, which functions as a load carrying layer, on a comparatively soft basis and that method is characterized by the fact that, by pressing down specifically formed bodies into the surface of the basis, depressions are brought about which are filled with part of the concrete mass used for the casting of the concrete slab, the size and the distance apart of the depressions being such that a shift of the two layers is prevented by the indentation effect between the layers. However, this method only serves the purpose of bringing about a load carrying layer rather than an attrition layer.

Danish Patent Specification 95,179 describes a method of constructing concrete lanes in which the foundation is covered by a layer consisting of at least two films of solid organic polymer plastics material, whereupon a mixture of freshly prepared concrete is placed on the layer and the concrete mixture is allowed to set. In the patent specification it is mentioned that it is known to place an intermediate layer of asphalt or paper between the lane and its foundation. However, in this case a real basis of asphalt is not concerned but only a thin film.

Finally Danish Patent Specification 143 037 describes a method of coating concrete bridges in which the uppermost castings or layers, which are normally of asphalt, may be of concrete and are placed upon a draining asphalt layer. Also in this case, however, only a thin asphalt layer is concerned and the coating is specifically intended for exclusively concrete bridges and similar constructions.

The present invention provides a method of preparing a thin layer of concrete on asphalt in which there is imparted to the asphalt a coarse and rough surface structure, for instance by milling or treatment with a spike drum whereupon the casting of a thin layer of concrete takes place which comprises fibres or in another way is reinforced whereupon the concrete is subjected to both ramming and vibration. In this way is obtained a light coloured road topping by use of domestic materials.

Preferably, pre-compression is imparted to the material in the road making machine used, whereupon final compression takes place by passage of a special vibration beam which is fit for both directional ramming and high frequency vibration.

In the concrete material used the maximum grain size of the stone material is suitably 1/3-1/4 of the thickness of the attrition layer and all grains of the stone material have at least a size which is half the maximum grain size. The maximum grain size of the sand fraction should be less than 1/4 of the maximum grain size of the stone material.

The invention will be further illustrated through the Example which follows.

EXAMPLE It is intended to repair the attrition layer of a road in which the traffic has brought about tearing off of stones, with cracks and crevices along the edges.

The road is of the following construction: 4 cm attrition layer of asphaltic concrete 7 cm gravel/asphaltic concrete of a first type 11 mm gravel/asphaltic concrete of a second type 15 cm mechanically stabilized gravel 40 cm ballast gravel.

The repair proceeds as follows: The asphalt attrition layer is milled to the depth required for obtaining a rectilinear and well defined basis having a coarse and rough structure.

The milled-off surface is subjected to thorough cleaning, if desired high pressure flushing.

A concrete attrition layer is spread in a thickness of 4 cm by means of an asphalt road making machine, the consistency of the material being dry and gravel-like.

The stone material used is a granite material having a grain size of 8-11 1 mm.

The sand material used has a maximum grain size of 2 mm.

The reinforcement material of the concrete is polypropylene fibres.

Pre-compression is imparted to the material in the road making machine and final compression is brought about by passage of a vibration beam which is fit for both directional ramming and high frequency vibration.

After final compression the material is sealed or protected in some other way against desiccation.

The road is opened to the traffic when the bending strength of the attrition layer has been attained.

1. A method of preparing a thin concrete layer on asphalt, in which a coarse and rough surface structure is imparted to the asphalt, a thin layer of concrete is cast which contains fibres or is reinforced in some other way, and the concrete is both rammed and vibrated.

2. A method as claimed in claim 1, in which the concrete is subjected to pre-compression, followed by final compression by means of a vibrator beam which is fit for both directional ramming and high frequency vibration.

3. A method as claimed in claim 1 or 2, in which the stone fraction of the concrete has a maximum grain size of 1/3-1/4 of the thickness of the concrete layer and a minimum grain size of at least half the maximum grain size, and the sand fraction has a maximum grain size which is at most 1/4 of the maximum grain size of the stone material.

4. A method as claimed in any of claims 1 to 3,

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Preparing a concrete layer on asphalt This invention relates to a method of preparing a thin concrete layer, constituting an attrition layer, on asphalt. Danish Patent Specification 139 1 64 describes a method of casting a concrete slab, which functions as a load carrying layer, on a comparatively soft basis and that method is characterized by the fact that, by pressing down specifically formed bodies into the surface of the basis, depressions are brought about which are filled with part of the concrete mass used for the casting of the concrete slab, the size and the distance apart of the depressions being such that a shift of the two layers is prevented by the indentation effect between the layers. However, this method only serves the purpose of bringing about a load carrying layer rather than an attrition layer. Danish Patent Specification 95,179 describes a method of constructing concrete lanes in which the foundation is covered by a layer consisting of at least two films of solid organic polymer plastics material, whereupon a mixture of freshly prepared concrete is placed on the layer and the concrete mixture is allowed to set. In the patent specification it is mentioned that it is known to place an intermediate layer of asphalt or paper between the lane and its foundation. However, in this case a real basis of asphalt is not concerned but only a thin film. Finally Danish Patent Specification 143 037 describes a method of coating concrete bridges in which the uppermost castings or layers, which are normally of asphalt, may be of concrete and are placed upon a draining asphalt layer. Also in this case, however, only a thin asphalt layer is concerned and the coating is specifically intended for exclusively concrete bridges and similar constructions. The present invention provides a method of preparing a thin layer of concrete on asphalt in which there is imparted to the asphalt a coarse and rough surface structure, for instance by milling or treatment with a spike drum whereupon the casting of a thin layer of concrete takes place which comprises fibres or in another way is reinforced whereupon the concrete is subjected to both ramming and vibration. In this way is obtained a light coloured road topping by use of domestic materials. Preferably, pre-compression is imparted to the material in the road making machine used, whereupon final compression takes place by passage of a special vibration beam which is fit for both directional ramming and high frequency vibration. In the concrete material used the maximum grain size of the stone material is suitably 1/3-1/4 of the thickness of the attrition layer and all grains of the stone material have at least a size which is half the maximum grain size. The maximum grain size of the sand fraction should be less than 1/4 of the maximum grain size of the stone material. The invention will be further illustrated through the Example which follows. EXAMPLE It is intended to repair the attrition layer of a road in which the traffic has brought about tearing off of stones, with cracks and crevices along the edges. The road is of the following construction: 4 cm attrition layer of asphaltic concrete 7 cm gravel/asphaltic concrete of a first type 11 mm gravel/asphaltic concrete of a second type 15 cm mechanically stabilized gravel 40 cm ballast gravel. The repair proceeds as follows: The asphalt attrition layer is milled to the depth required for obtaining a rectilinear and well defined basis having a coarse and rough structure. The milled-off surface is subjected to thorough cleaning, if desired high pressure flushing. A concrete attrition layer is spread in a thickness of 4 cm by means of an asphalt road making machine, the consistency of the material being dry and gravel-like. The stone material used is a granite material having a grain size of 8-11 1 mm. The sand material used has a maximum grain size of 2 mm. The reinforcement material of the concrete is polypropylene fibres. Pre-compression is imparted to the material in the road making machine and final compression is brought about by passage of a vibration beam which is fit for both directional ramming and high frequency vibration. After final compression the material is sealed or protected in some other way against desiccation. The road is opened to the traffic when the bending strength of the attrition layer has been attained. CLAIMS

1. A method of preparing a thin concrete layer on asphalt, in which a coarse and rough surface structure is imparted to the asphalt, a thin layer of concrete is cast which contains fibres or is reinforced in some other way, and the concrete is both rammed and vibrated.

2. A method as claimed in claim 1, in which the concrete is subjected to pre-compression, followed by final compression by means of a vibrator beam which is fit for both directional ramming and high frequency vibration.

3. A method as claimed in claim 1 or 2, in which the stone fraction of the concrete has a maximum grain size of 1/3-1/4 of the thickness of the concrete layer and a minimum grain size of at least half the maximum grain size, and the sand fraction has a maximum grain size which is at most 1/4 of the maximum grain size of the stone material.

4. A method as claimed in any of claims 1 to 3, in which the coarse and rough structure is imparted by miiling.

5. A method of preparing a thin concrete layer on asphalt, substantially as described in the Example given.