Road-Building Concretes Incorporating Fly-Ash or Slag


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Title: Road-Building Concretes Incorporating Fly-Ash or Slag

Author(s): G. Bordonado and J.L. Nissoux

Publication: Special Publication

Volume: 79


Appears on pages(s): 471-494

Keywords: cements blast furnace slag; compacting; concrete pavements; fly ash; performance; portland pozzolan cements; portland slag .

Date: 5/1/1983

The energy crisis calls for economy in all fields. Roadmaking, which consumes a great amount of materials of all kinds, is of all civil engineering sectors one in which the constructor can - all other things being equal - take the greatest technical risks. In this field, innovation is permanent, and the For more than 20 years past, French roadmaking techniques have made use of industrial wastes, those whose properties make them veritable hydraulic or pozzolanic binders : blast furnace lag and fly-ash. Some years ago, under the pressure of the need to economize materials and energy, there was a rediscovery of the value of rigid structures consuming a lesser quantity ofmaterials, using binders involving a lesser consumption of energy, and above all not requiring a bituminous wearing course. By extrapolating operational techniques, internally vibrated pavement concrete and compacted treated gravels, an attempt was made to establish a better recognition of the binding properties of slag and fly-ash in order to achieve highly economical techniques of rigid pavement construction. Some motorways were recently built in which cement was re-placed by around 30 % by fly-ash or pulverized slag. This communication describes how the characteristics of these concretes were worked out, how they were obtained and applied throughout the im-technique. plementation of the project, how systems of control were adapted, and what difficulties were encountered. Simultaneously, a promising evolution of the technique of rigid pavements having recourse to the pozzolanic properties of fly-ash is emerging : compacted concrete. This communication indicates the principal properties of the material as revealed in the laboratory and on experimental sites, together with the difficulties encountered and the possibilities of development of this Taking advantage of the binding properties of industrial by-products does not present major technical difficulties provided that in each case allowance is made for contractual demands, means of control, and in certain cases methods of production and laying. The risks assumed by the contractor are higher than if he uses a standardized industrial product, guaranteed by the producer ; but in many cases, the economy achieved amply offsets the additional control required to cover those risks, passage from the laboratory to the working site is a very rapid one.