GB2144113A

GB2144113A - Road making composition

Info

Publication number: GB2144113A
Application number: GB08416484A
Authority: GB
Inventors: Graham Vivien Walters
Original assignee: Ecc Quarries Ltd; ECC Quarries Ltd
Current assignee: Ecc Quarries Ltd; Camas UK Ltd
Priority date: 1983-06-29
Filing date: 1984-06-28
Publication date: 1985-02-27
Also published as: GB8416484D0; GB2144113B

Abstract

A composition suitable for roadmaking is made by mixing wet china clay waste with a bitumen emulsion in water at ambient temperature. The composition is particularly suitable for use as the base course in roads.

Description

SPECIFICATION Road making compositions This invention relates to roadmaking compositions and to methods of making them.

Many roads are made by laying a base course on a suitably prepared foundation, and then laying a wearing course, providing the running surface, on top of the base course. The base course may, for example, comprise two separately laid and compacted layers each having a thickness of approximately 10 cm. The wearing course may have a thickness of approximately 4 cm.

It is known to lay the wearing course in the form of a composition comprising particulate stone which has been coated by a bitumen emulsion, and similar compositions have been proposed for the base course. After laying and compaction, the emulsion breaks, allowing the bitumen droplets to coalesce, the water in the emulsion then being driven off, leaving the bitumen as a rigid mass. The characteristics of the emulsion depend on the grade of bitumen, the nature of the emulsifier and the relative proportions of the ingredients.

The coating of stone chips has required sophisticated plant representing a large capital investment. The stone must be screened and dried, and then mixed with the bitumen emulsion in a special mixer. The drying step, which requires a great deal of energy, is necessary because up to now it has been assumed that bitumen emulsions will not coat wet stone.

According to one aspect of the present invention there is provided a method of making a composition suitable for roadmaking, the method comprising mixing, at ambient temperature, china clay waste with an emulsion of bitumen in water.

According to another aspect of the present invention there is provided a method of making a composition suitable for roadmaking comprising: a) providing a pugmill at a location adjacent a tip of china clay waste, b) mixing the china clay waste with a bitumen emulsion in the pug mill at ambient temperature, without performing any screening, drying or heating of the china clay waste.

The invention also provides a composition suitable for road making when made by this method, and a road made from the composition.

China clay waste normally comprises sand, substantially all of the particles of which will pass through a 20 mm screen; at least 85% of the particles will also pass through a 5 mm screen.

Thus the invention encompasses the use, for base courses, of considerably finer particulate stone than has hitherto been regarded as acceptable for this purpose.

China clay waste usually consists to a significant extent of mica. For example the proportion of mica by weight may be in the range 1 to 35%, commonly more than 10%, and, in the Examples which will follow, more than 15%. Materials including mica are regarded as being unsuitable for coating with bitumen emulsions.

In general, the mineral compositions and particle size distribution are as follows: Component percentage by weight Kaolinite 0-15 Mica 1-35 Quartz 20-85 Felspar 1-40 Tourmal ine 1-20 Size percentage by weight larger than 20mm 0-5 5mm to 20mm 0-10 2mm to 5mm 10-50 lmm to 2mm 15-25 O.25mm to lmm 20-35 smaller than 0.25mm 5-25 China clay waste is available in large quantities in clay-producing areas, and is invariably wet.

Nevertheless, it can be used, in accordance with the present invention, without any pretreatment by way of screening or drying, i.e. it can be taken direct from the tip and satisfactorily coated with bitumen emulsion.

In some circumstances, benefits may be obtained by including limestone waste or scalpings in the mixture. Limestone waste tends to consist of larger particles than china clay waste, and so the relative proportions of the two materials can be adjusted to meet required particle size specifications.

The mixing of the china clay waste and the bitumen emulsion can be effectively achieved, without needing to heat either the stone or the emulsion, in a conventional pug-mill, which means that the capital cost of the coating equipment can be considerably reduced compared to that of a conventional coating plant. Furthermore, it becomes practical to carry out the coating operation at the china clay waste tip, which results in a saving in transport costs which would otherwise be incurred in transporting the china clay waste to the conventional type of coating plant.

The bitumen emulsion to be used in accordance with the method of the present invention muJt be formulated so that it will satisfactorily coat wet stone. Preferably, a relatively hard grade of bitumen is used so as to provide a hard base course.

The bitumen emulsion may contain 0.5 to 5% (preferably 2%) by weight of a cationic surfactant which enables the bitumen to coat and adhere to the predominantly negatively charged surface of the particles of the china clay waste. The surfactant is preferably an acid (such as hydrochloric, acetic or formic acid) salt of a fatty acid (with 12-20 carbon atoms) amido amine condensate. The fatty acid is most preferably oleic acid or tallow or hydrogenated tallow. Other possible surfactants are: a) water soluble acid salts of fatty alkyl diamines or polyamines (especially hydrochloric, acetic or formic acid salts) b) neutralized imidazoline salts c) alkoxylated forms of (a) or (b) d) alkoxylated fatty amine derivatives e) quarternary ammonium salts and their alkoxylated derivatives.

By suitably selecting the bitumen and the surfactant, it is possible to produce a composition which will set hard soon after laying (i.e. in about half a day) to provide a trafficable surface capable of withstanding heavy lorries. Consequently, a composition in accordance with the present invention may be used to provide temporary roads in, for example, building developments such as housing estates, to provide access for construction and service vehicles during building. Such roads can than be removed when the development is complete, to be replaced by permanent roads.

For a better understanding of the present invention, and to show how it may be carried into effect, reference will now be made to the following Examples.

EXAMPLE 1 A road making composition was made by mixing bitumen emulsion with waste sand left after extracting china clay from Lee Moor in Cornwall. The sand had the following mineral content and particle size distribution: Component percentage by weight Kaolinite 2.7 Mica 16.4 Quartz 46.0 Felspar 26.8 Tourmal ine 8.0 Size percentage by weight larger than 20mm 0.8 5mm to 20mm 4.9 2mm to 5mm 25.9 Imin to 2mm 19.5 0.25mm to Imin 30.6 smaller than 0.25mm 18.3 The sand was wet, and consisted predominantly of silica, having a significant proportion of mica. The sand and bitumen were mixed to give a composition comprising 5% bitumen emulsion to 95% sand, the bitumen comprising 60%, by weight, of the bitumen emulsion.The sand and bitumen emulsion were mixed in a pug-mill at ambient temperature, without any pretreatment of the sand.

After laying and compacting the resulting composition, it became hard and provided a strong layer suitable for use as a base course.

EXAMPLE 2 A composition was prepared as in Example 1, except sand left after extracting clay from Melba Pit in Cornwall was used instead of the sand from Lee Moor. The mineral composition and particle size distribution were as follows: Component percentage by weight Kaol ini te 5.5 Mica 15.7 Quartz 59.9 Felspar 6.1 Tourmal ine 12.8 Size percentage by weight larger than 20mm 0.3 5mm to 20mm 3.2 2mm to 5mm 42.7 lmm to 2mm 18.6 0.25mm to lmm 24.0 smaller than 0.25mm 11.1 Again, the resulting composition, after laying and compaction, provided a hard base course.

Claims

1. A method of making a composition suitable for road making, the method comprising mixing, at ambient temperature, china clay waste with an emulsion of bitumen in water.

2. A method as claimed in claim 1, in which the china clay waste consists of particles substantially all of which will pass through a screen having a nominal aperture of not more than 20 millimetres.

3. A method as claimed in claim 1 or 2, in which at least 85%, by weight, of the china clay waste consists of particles which will pass through a screen having a nominal aperture of 5 millimetres.

4. A method as claimed in any one of the preceding claims, in which the china clay waste has the following particle size distribution: Size percentage by weight larger than 20mm 0-5 5m to 20mm 0-10 2mm to 5mm 10-50 lmm to 2mm 15-25 0.25mm to lmm 20-35 smaller than 0.25mm 5-25

5. A method as claimed in claim 4, in which the china clay waste has a particle size range in accordance with Example I or Example II.

6. A method as claimed in any one of the preceding claims, in which the china clay waste comprises mica.

7. A method as claimed in claim 6, in which the china clay waste comprises at least 10% mica, by weight.

8. A method as claimed in any one of the preceding claims, in which the composition of the china clay waste is as follows: Component percentage by weight Kaolinite 0-15 Mica 1-35 Quartz 20-85 Felspar 1-40 Tourmal ine 1-20

9. A method as claimed in claim 8, in which the composition of the china clay is in accordance with Example I or Example II.

10. A method as claimed in any one of the preceding claims, in which limestone waste is mixed with the china clay waste and the bitumen emulsion to form the composition.

11. A method as claimed in any one of the preceding claims, in which the bitumen emulsion and the china clay waste are mixed in a pugmill.

1 2. A method as claimed in any one of the preceding claims, in which the bitumen emulsion includes a cationic surfactant.

1 3. A method of making a composition suitable for roadmaking comprising: a) providing a pugmill at a location adjacent a tip of china clay waste, b) mixing the china clay waste with a bitumen emulsion in the pugmill at ambient temperature without performing any screening, drying or heating of the china clay waste.

14. A method of making a composition suitable for road making as claimed in claim 1 and substantially as described herein.

1 5. A roadmaking composition made in accordance with any one of the preceding claims.

1 6. A road comprising at least one base course comprising a composition as claimed in claim

15.

1 7. A road as claimed in claim 16, which is a temporary road.