Hydraulic and earth engineering – Foundation
Patent
1984-11-02
1987-02-03
Corbin, David H.
Hydraulic and earth engineering
Foundation
52742, E02D 2708, E02D 2726, E04B 532
Patent
active
046406484
DESCRIPTION:
BRIEF SUMMARY
Most of the industrial floors (manufacture workshop floors, warehouse floors, garage floors, . . . ) are made of reinforced, surface-polished concrete.
These floors are made by spreading freshly prepared concrete onto a sheet of plastic material placed on the compacted foundation course, the reinforcement being placed either before or while the concrete is being placed.
The reinforcement also may be made up by adding steel fibers to the concrete during the mixing stage; in that way the concrete becomes homogeneous due to the fact that it is reinforced in all directions and that the fibers-concrete interface has a much greater surface area than in case of a conventional reinforcement.
The plastics sheet is placed on the compacted foundation course in order to reduce the friction coefficient of the slab on the ground and thus reduce the tensions due to shrinkage of the concrete.
The concrete-casting operation is followed with a surface-polishing stage which after termination provides the concrete with a mirror polish aspect, as known. The concrete then needs to be protected from too fast desiccation by means of a protective coating (improperly termed "curing") layer applied on the concrete immediately thereafter, with the purpose of retaining for the longest possible time all water which is not needed for chemical effects, in an effort to prevent savage crack-formations.
After the first hardening stage, the ultimate step involves creating in the slab startings of shrinkage cracks.
As a matter of fact, slabs of the kind described may be very large with surface areas of 5000 m.sup.2 or more and for that reason in many points of the slab, concrete shrinkage tensions will exceed the tensile strength of the concrete and result in the appearance of cracks.
In order to avoid these savage crack formations, it is of common use to provide saw cuts along rectangular meshes of 25 to 35 m.sup.2 surface to provide crack startings. The slab completed in that way shows discontinuities each of which is made of a saw-cut seam causing drawbacks such as breaking of the seams on use by passage of handling trucks, retentions of dirt and dust.
An important improvement of the floor or slab quality could be obtained by suppressing the shrinkage seams without however causing any crack formation.
According to the prior art, the industrial continuous concrete floor was prepared by spreading concrete onto a previously placed reinforcement armouring system.
The reinforcement generally used in that case consists of two planes of fine wire nettings assembled into cloths. Each of these planes of reinforcement must be as close as possible by the surfaces which define the volume of the industrial floor concrete body.
This causes difficulties in operation: using systems called distance pieces surface to be reinforced while constantly maintaining a minimum layer of concrete to cover the steel.
The difficulties encountered in positioning mainly result from the fact that the finished level of the industrial floor is strictly determined while the level of the foundation course supporting the reinforcement system is variable.
The purpose of the invention is to make an industrial floor of quality in continuous concrete having a surface area which may reach or exceed 5000 m.sup.2 and the thickness of which is identical with that of a conventional slab the concrete being provided with a homogeneous multidirectional reinforcement system obtained by mixing a minimum of fibers, for example steel fibers, to the concrete in the mixing stage.
For that purpose there is cast a totally free and independent slab by using a limited shrinkage concrete.
The fiber reinforcement system enables to limit the development of cracks.
The action of such reinforcement is more durable when using fibers which are provided with anchorage means for anchoring them to the concrete and more particularly fibers of a diameter between 0.5 and 1 mm for a length respectively between 40 and 60 mm. These fibers may be provided with anchorage corrugations or ondulations spread over their
REFERENCES:
patent: 2078289 (1937-04-01), Sloan
patent: 3561175 (1971-02-01), Best et al.
Bouwwereld-C. Misset N.V. Doetinchem (The Netherlands), vol. 73, No. 10, May 13, 1977, pp. 38-41.
W. H. Taylor: "Concrete Technology and Practice", American Elsevier, New York, 1965, pp. 426-429.
Destree Xavier P.
Lazzari Angelo A.
Corbin David H.
Eurosteel s.a.
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