IE65353B1

IE65353B1 - Method of producing an ultrathin bituminous road surfacing

Info

Publication number: IE65353B1
Application number: IE940204A
Authority: IE
Inventors: Pierre Bense; Jean-Francois Patte; Jean-Paul Fort
Original assignee: Screg
Priority date: 1994-02-21
Filing date: 1994-03-07
Publication date: 1996-05-15
Also published as: AU669260B2; NZ260634A; FR2716470B1; FR2716470A1; IE940204A1; AU5769794A

Abstract

The method described consists in spreading a thick layer of bituminous binder and then, immediately after, in applying coated chippings, which enables an ultrathin road surfacing to be obtained, the thickness of which is at most equal to 2.5 times the maximum size of the chippings.

Description

The pre 3ent invention relates to a method of Ιρβ ult r a thin bituminous road surfacing, of the -type —ia- wh-ieh ~a bituminous-binder sealing and bonding layer is applied to the road to be surfaced, and, immediately after, hot coated chippings are spread over this binder layer and then these coated chippings are precompacted and smoothed with the aid of a finishing table.

The basic principle of such a method is described in EP-A-49,260, and the object of the invention is to provide an improvement to this technique, enabling ultrathin bituminous surfacings to be obtained having a thickness which can be as low as 10 to 20 mm. For this purpose, the subject of the invention is a method of the aforementioned type, characterized in that, at each given location on the road: (a) the ratio of the bitumen quantity contained in the bituminous-binder sealing and bonding layer to the total bitumen quantity used lies between approximately 15 and 50%; (b) the bituminous surfacing has a thickness at most equal to 2.5 times the maximum size of the chippings; (c) the bituminous-binder sealing and bonding 25 layer is applied in a quantity allowing metering with pure bitumen lying between 0.3 and 1.2 kg/m2 of pure binder; (d) the coated chippings are made up of chippings coated by means of a bituminous mortar consisting of sand, of fines, of possible additives, such as fibres, and of the bitumen to which an adhesion-promoting agent is possibly added; (e) the operations of application of the bituminous-binder eealing and bonding layer and of spreading of the coated chippings are performed in less than 5 seconds for both operations, whereas the completion of the operation of precompacting and smoothing with the aid of a finishing liable occurs at most seconds after the application of the binding layer; - 2 65353 and (f) the speed of advance of the surfacing site lies between 5 and 30 m/min.

The method according to the invention may include one or more of the following characteristics: - the completion of the operation of precompacting and smoothing with the aid of a finishing table occurs 10 to 30 seconds after the application of the binding layer; - the speed of advance of the surfacing site lies between 20 and 30 m/min; - the binding layer is applied in a quantity allowing metering with pure bitumen lying between 0.4 and 0.7 kg/m2; - the bitumen used in the emulsion, and possibly in the bituminous binder, is a pure bitumen modified by approximately 3% of an elastomer; - the bitumen of the binding layer is an 80/100 bitumen (French Standards NFT 66-004 and NFT 66-008) modified by an elastomer; - the bitumen of the binding layer is a 180/200 bitumen (French Standards NFT 66-004 and NFT 66-008) modified by an elastomer; - the emulsion has an Engler viscosity at 25°C (French Standard NFT 66-020) lying between 10 and 20, and contains at most 0.25% of particles of size lying between 0.16 and 0.63 mm and at most 0.10% of particles of size greater than 0.63 mm; the aggregates have a maximum size lying between 6.3 mm and 19 mm; - the aggregates have a LOS ANGELES abrasion coefficient (American Standard ASTM C 131) less than 25 for moderate traffic, less than 200 heavy lorries per day, and less than 20 for heavy traffic, greater than this value, and an accelerated polishing coefficient (French Standard NFP 18-575) greater than 50, and a flattening coefficient (French Standard NFP 18-561) less than 20 for moderate traffic, less than 200 heavy lorries per day, and less than 15 for heavy traffic, greater than this value, and a crushing index of practically 100%.

An example of implementation of the invention will now be described with regard to the appended drawing, the single figure of which represents diagrammatically a machine intended for the implementation of the method according to the invention.

The machine 1 shown in the drawing is selfpropelled. It comprises a frame 2 mounted on several axles 3 and carrying, from the front to the rear: - an idler roller 4, of horizontal and transverse axis, which serves to push a tip-up lorry for supplying coated chippings; - a hopper 5 for receiving the coated chippings; - a control cabin 6; - an intermediate box 7 for the buffer-storage of the coated chippings; - an emulsion tank 8; - an emulsion spray boom 9, of width which can be adjusted by virtue of a telescopic structure. This boom comprises a series of spray nozzles, each of which includes an unblocking needle connected to means of actuation (not shown), for example by manual control or under the control of a blockage detector (not shown); - two feed screws 10 for transverse spreading of the coated chippings; and - a raisable vibrating smoothing table 11 articulated onto the frame by means of two longitudinal arms 12.

For conveying the coated chippings, there are provided a first feed screw 13, surrounded by a cylindrical casing 14, the axis of which rises up from the bottom of the hopper 5 and which emerges, at its upper part, in the box 7, and a second, horizontal, feed screw 15 which extends in a mid-position along the entire length of the bottom of the box 7 as far as a chute 16 for discharging the coated chippings opposite the spreading screws 10.

In addition, as shown, it is also possible to provide, in the box 7, a levelling feed screw 17.

An electricity generator 18 has also been shown diagrammatically in the drawing, this supplying power to the heating resistance elements (not shown) of the box 7, the tank 8 and the feed screws 13, 15 and 17.

A description will now be given of the installation, in a single pass and at high speed, by means of the machine 1, of an ultrathin bituminous carpet, of approximately 10 to 20 mm in thickness and, more generally, having a thickness at least equal to 2.5 times the maximum size of the chippings used, this carpet ensuring, in a long-lasting manner, adhesion and impermeability and a low running noise. The main application of this method is the repair of roads, the adhesion and impermeability of which it is desired to restore, but it may also be used as surfacing for a new road. The surfacing can be used for all types of road traffic.

By reason of its very small thickness, the surfacing requires a support which is correctly profiled and, possibly, reprofiled. This support must be clean and, beforehand, swept and exposed to suction.

During the operation of the machine, the latter advances at a constant speed of from 5 to 30 m/min, and preferably from 20 to 30 m/min, in the direction of the arrow F indicated in the drawing. A succession of tip-up lorries (not shown) discharge, into the hopper 5, hot coated chippings, at a temperature from 160 to 180°C, these tip-up lorries being pushed by the roller 4.

The screw 13 conveys these coated chippings into the buffer-box 7, from where they are conveyed by the screw 15 right into the chute 16, which discharges them in front of the inside ends of the screws 10. The latter spread out the coated chippings laterally, and the surfacing is compacted and smoothed by the table 11. If a major build-up of coated chippings occurs in the box 7, levelling may be carried out by means of the screw 17.

Just in front of the lower end of the chute 16, the boom 9, supplied with bituminous emulsion via the tank 8, sends fan-shaped jets of this emulsion over the entire width to be surfaced, behind the rear wheels of the machine, forming a sealing and coated-chippingbonding layer. The design is such that, taking into account the speed of advance of the machine, the operations of application of the bonding and sealing layer and of the coated chippings are performed in less than 5 seconds for both operations. Thus, the hot coated chippings instantly bring the emulsion to the boil, before it could be broken, the sudden rise in the temperature causing the breaking of the emulsion to be accelerated. This ensures strong adhesion, according to the teaching of the aforementioned EP-A-49,260.

The metering with residual pure binder depends on the texture and on tbe porosity of the support: it varies from 0.3 to 1.2 kg/m2 of residual binder.

Installation of the surfacing is completed by conventional rolling.

The constituents used in this method will now be described in more detail. (1) Binding layer: This binding layer is a cationic bitumen emulsion consisting of a bituminous binder, which is a bitumen modified by at least 3% of a latex or of an SBS copolymer, in water, with 62 to 65% of residual binder after breaking the emulsion and eliminating the water.

The bitumen is an 80/100 or 180/220 pure bitumen, in accordance with Table I hereinbelow: TABLE I Method 80/100 180/220 • 25 °C penetrability, 100 g, 5 s, 1/10 mm NFT 66-004 70-100 180-220 • Ring-and-ball softening point, °C NFT 66-008 42-48 34-43 • 60°C viscosity, poise 1500±300 250±50 The fine and homogeneous emulsion is in accordance with the specifications of Table II hereinbelow: - 6 TABLE II TEST METHOD Min Max 1. Elastomer content o£ the distillation residue, % by weight 3.0 2. Water content, % NET 66-023 35 39 3. 25°C SSF viscosity 20 65 4. 25 °C Engler viscosity NET 66-020 10 20 5. 7-day decantation storage stability, % NET 66-022 5 6. Demulsifibility, 0.8 % sodium dioctyl sulphosuccinate, 35 ml, % ASTM D 40 7. Charge o£ the particles NET 66-021 positive 8. Homogeneity o£ particles greater than 0.63 mm; particles between 0.63 mm and 0.16 mm NET 66-016 0.10% 0.25% 9. Breaking index NET 66-017 110 (2) Bitumwn-coated chippings: The bitumen-coated chippings comprise, on the one hand, chippings and, on the other hand, a coating mortar consisting of crushed sand, possibly of added fines, and of a bituminous binder.

The chippings most commonly used are 4/6, 6/10 or 6/12 chippings, with the particle size distributions of Table III hereinbelow: TABLE III SCR KWHS mm 4/6 6/10 6/12 19 - 100 100 12.7 - 100 85-100 9.5 100 85-100 25-50 6.3 85-100 0-15 0-15 4.75 25-50 0-10 0-10 4.00 0-15 0-3 0-3 2.36 0-3 - - 2.00 0 - - I - Ί The properties of the chippings to be used are collated in Table IV hereinbelow: TABLE IV TESTS MEXBOD MODERATE TRAFFIC < 200 heavy lorries per day HBAVT TRAFFIC > 200 heavy lorries per day toe Angeles abrasion coefficient ASTM C 131 < 25 < 20 Accelerated polishing coefficient WFP 18-575 > 50 > 50 Water absorption, % WFP 18-555 < 2 < 2 Flattening coefficient WFP 18-551 < 20 < 15 Crushing index 100 % 100 % Cleanliness (% exceeding 0.5 nm) < 1 < 1 Decoating test operating mode LCTC > 95 % > 95 % The sand used is 100 % crushed. Its sand equivalent, according to the NFP 18-598 standard, is greater than 60. Its particle size distribution is that of Table V hereinbelow: TABLE V SCREBBS (mm) UBDERSIZB, BT WEIGHT 4.75 100 4.00 100 2.36 90-100 2.00 85-95 1.18 60-80 0.60 45-60 0.30 30-40 0.15 20-30 0.075 15-25 If the sand does not contain sufficient fines, that is to say particles less than 80 μιη, fines are added, these being chosen for example, from hydrated lime, fly-ash, recovery fines and cement. These fines will all have a size less than 0.15 mm, with 80 % passing through the 75 μχη screen.

The coating bitumen, depending on the climatic conditions and the intensity of the traffic, is preferably an 80/100 or 60/70 pure bitumen (French Standards NFT 66-004 and NFT 66-008), possibly modified by an elastomer. The bitumen possesses the properties indicated in Table VI hereinbelow: TABLE VI TEST METHOD 80/100 60/70 Penetration, 25 °C, 100 g, 5 s, minimum NFT 66-004 70-100 50-70 Viscosity, 60°C, poise ASTM D 3381 1,500 i 300 2,000 t 400 Ring-and-ball softening point, °C NFT 66-008 42-48 45-51 The mixture, namely the coated chippings feeding the machine, contain approximately 5.2 % of bitumen with respect to the total weight of the dry materials. Its particle size distribution is provided by Table VII hereinbelow:

Claims

1. Method of producing an ultrathin bituminous road surfacing, of the type in which a bituminous-binder sealing and bonding layer is applied to the road to be surfaced, and, immediately after, hot coated chippings are spread over this hinder layer and then these coated chippings are precompacted and smoothed with the aid of a finishing table, characterized in that, at each given location on the road; (a) the ratio of the bitumen quantity contained in the bituminous-binder sealing and bonding layer to the total bitumen quantity used lies between approximately 15 and 50%; (b) the bituminous surfacing has a thickness at most equal to 2.5 times the maximum size of the chippings; (c) the bituminous-binder sealing and bonding layer is applied in a quantity allowing metering with pure bitumen lying between 0.3 and 1.2 kg/m 2 of pure binder; (d) the coated chippings are made up of chippings coated by means of a bituminous mortar consisting of sand, of fines, of possible additives, such as fibres, and of the bitumen to which an adhesion-promoting agent is possibly added; (e) the operations of application of the bituminous-binder sealing and bonding layer and of spreading of the coated chippings are performed in less than 5 seconds for both operations, whereas the completion of the operation of precompacting and smoothing with the aid of a finishing table occurs at most 30 seconds after the application of the binding layer; and (f) the speed of advance of the surfacing site lies between 5 and 30 m/min.

2. Method according to Claim 1, characterized in that the completion of the operation of precompacting and smoothing with the aid of a finishing table occurs 10-30 seconds after the application of the binding layer.

3. Method according to Claim 1, characterized in that the speed o£ advance of the surfacing site lies between 20 and 30 m/min.

4. Method according to any one of the preceding claims, characterized in that the binding layer is applied in a quantity allowing metering with pure bitumen lying between 0.4 and 0.7 kg/m 2 .

5. Method according to any one of the preceding claims, characterized in that the bitumen used in the emulsion, and possibly in the bituminous binder, is a pure bitumen modified by approximately 3 % of an elastomer.

6. Method according to any one of the preceding claims, characterized in that the bitumen of the binding layer is an 80/100 bitumen (French Standards NFT 66-004 and NFT 66-008) modified by an elastomer.

7. Method according to any one of Claims 1 to 5, characterized in that the bitumen of the binding layer is a 180/200 bitumen (French Standards NFT 66-004 and NFT 66-008) modified by an elastomer.

8. Method according to any one of the preceding claims, characterized in that the emulsion has an Engler viscosity at 25°C (French Standard NFT 66-020) lying between 10 and 20, and contains at most 0.25 % of particles of a size lying between 0.16 and 0.63 mm and at most 0.10 % of particles of a size greater than 0.63 mm.

9. Method according to any one of the preceding claims, characterized in that the aggregates have a maximum size lying between 6.3 mm and 19 mm.

10. Method according to any one of the preceding claims, characterized in that the aggregates have a Los Angeles abrasion coefficient (American Standard ASTM C 131) less than 25 for moderate traffic, less than 200 heavy lorries per day, and less than 20 for heavy traffic, greater than this value, and an accelerated polishing coefficient (French Standard NFP 18-575) greater than 50, and a flattening coefficient (French Standard NFP 18561) less than 20 for moderate traffic, less than 200 heavy lorries per day, and less than 15 for heavy » * - 12 traffic, greater than this value, and a crushing index of practically 100 %.

11. * A method according to Claim 1 of producing an ultrathin bituminous road surfacing, substantially as hereinbefore described with reference to the accompanying drawings.

12. An ultrathin bituminous road surfacing whenever obtained by a method claimed in a preceding claim.