Technical guide - Continuous hot mix production
The French expertise
The document presents the French experience on the continuous manufacture of hot-coated materials. The technique is strong of thirty years of developments and concerns today half of the hot-coated materials production. This development has been made possible and easiness by a joint work between the plants manufacturers, the contractors of works, the awarding authorities and contract managers.
The document presents the French experience on the continuous manufacture of hot-coated materials. The technique is strong of thirty years of developments and concerns today half of the hot-coated materials production. This development has been made possible and easiness by a joint work between the plants manufacturers, the contractors of works, the awarding authorities and contract managers.
The bituminous mixing plants are on the whole one half - thousand of units, 20 % are mobile plants, in majority continuous, and 80 % are stationary plants, of which 35 % are continuous.
The expansion of the continuous technique is at once due to the large national programs of new and maintenance works towards 1970, to the formalization of the quality requirements on the production of aggregates and on the composition of materials, and to the successive technological improvements on the continuous plants. These last allow today the incorporation of some recycled aggregates until 50 % of the end product, and respect the strictest environmental standards dealing with release of gas.
After a brief recall of the two types of process: continuous and discontinuous, and a detailed description of the components and the working of a continuous plant, the document describes two real cases of sites.
Summary
1. Brief history of the technique . . . . . . . . . . . . . . . . . . . . . . . . . . .5
2. The types of hot mix process . . . . . . . . . . . . . . . . . . . . . . . . . . .7
3. Description of the equipment . . . . . . . . . . . . . . . . . . . . . . . . . . .8
3.1 Aggregate metering. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
3.2 Belt flowmeter (conveyor belt scale). . . . . . . . . . . . . . . . . . . . . .9
3.3 Feed bin sizing method. . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.4 The drying and coating mixer: the heart of the system . . . . . . . . . . . 11
3.5 Bitumen metering management. . . . . . . . . . . . . . . . . . . . . . . 13
3.6 Handling dusting filler and foreign filler . . . . . . . . . . . . . . . . . . 13
3.7 Bitumen concrete storage. . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.8 Automatic operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.9 The continuous process and the environment. . . . . . . . . . . . . . . . 15
3.10 Mobility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4. Examples of possible strategies to satisfy the market . . . . . . . . . . . . . . 17
4.1 High tonnage motorway construction in open country . . . . . . . . . . . 17
4.2 Motorway works in an urban area:maintenance work on the carriageways of the Paris «Boulevard Peripherique» . . . . . . . . . 19
4.3 Production of recycled products: environmental considerations . . . . . . . 21
5. Guide for a road investor . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
6. Bibliography: standards covering continuous hot mix production. . . . . . . . . . 23
6.1 Equipment standards. . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
6.2 Equipment test standards. . . . . . . . . . . . . . . . . . . . . . . . . . 23
6.3 Equipment approval standards . . . . . . . . . . . . . . . . . . . . . . . 23
6.4 Calibration standards. . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
6.5 Manufacturing and implementation standards . . . . . . . . . . . . . . . 24
6.6Information bulletins. . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
6.7 Main approved and experimental reference methods for gaseous emissions from fixed sources . . . . . . . . . . . . . . . . . . 24
