This page was translated by SYSTRAN      (comments, feedback ...)

An additional progress in the fall of the price of construction of a network of tram. While revolutionizing the installation of the embedded rails regularly, the new guided trolley bus of Nancy, for example, will become more expensive than a line of tram!!!!

Cheer the Engineers of the BTP, continue thus...

Concrete: B45 fibred for the tram of Orleans

The synthetic fibres get a better resistance of the concrete to cracking and the vibrations in service.

More than 15 000 m3 of concrete fibré B45 are currently implemented in Orleans, for the southern part of the first line of tram, whereas, on the northern section, the companies proposed a normal concrete B30. «It is a deliberated choice, explains Jean-Claude Butstraen, head of tram project to the company TSO which carries out 10 km of ways (on a layout of 18 km), since the market did not stipulate it. We chose it for reasons of results and comfort of work. »
The fibré concrete makes it possible to eliminate the station from reinforcement, since the fibres replace the steel fabric.
The advantages of the fibré concrete are now known: profits as regards tensile strength, and impact resistance and to ageing. But the principal asset is initially to limit the shrinkage cracks, and thus to reduce the water infiltrations. «Allied with a curing agent to avoid the too fast catch of the concrete, especially when the weather is hot, the synthetic fibres protect from cracking with 80%, against 7% with a steel fabric », explains Bernard Delabreche (Piéri company). «It is a considerable advantage, considers Jean-Claude Butstraen, because the installation of the lattices represents a heavy and sometimes risky work: it is necessary to store, cut out the lattice with risks of accidents, defects of installation or bad vibrating. The fibré concrete is thus much simpler. »In spite of a slightly higher cost gross (than the representative of TSO quantifies to 3 to 4 %), the final result is considered to be completely «painless financially», after incorporation of the indirect profits like the labour-savings. The polypropylene fibres 19 mm length (comparable with the granulometry of the concrete) are mixed directly at the concrete mixer, without particular preparation for the casting, with a proportioning of 900 G / m3 While drying, these fibres inalterable and resisting the alkalinity of the concrete perfectly bind the components of the concrete between them and support a withdrawal without cracks.
On the building site, the company made studies of wrenching: «We do not have any concern with the behaviour of anchorings, higher of 30% than what is required. It much better than with is non-fibré.»Other favours: the fibré concrete resists the vibrations by absorbing energy more: an asset of size for a tram.

JEAN-jacques TALPIN "Le Moniteur du BTP" of 31-12-99