Static structures (e.g. – buildings) – Cast in situ composite slab
Patent
1994-12-09
1997-11-18
Friedman, Carl D.
Static structures (e.g., buildings)
Cast in situ composite slab
52378, 52426, 52439, 5274509, 249 18, 249 78, 249113, 249141, 264 35, 264277, 264404, E04G 1106, E04B 254
Patent
active
056875223
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a formwork constructed of prefabricated elements, intended for building a concrete wall. The formwork includes two parallel walls that define a space that is filled with concrete laden with sand and large aggregates. This invention also includes a concrete wall, and in particular a heating wall, built by the formwork.
2. Description of Prior Art
Concrete includes a mixture of cement, sand, large stone aggregates of variable sizes, such as gravel, and water. This mixture is heterogeneous, and each of its constituents, except for the mixture of water and cement, is independent. The workability of concrete, that is, the ability of concrete to perfectly fill a formwork, depends on the ease with which each of the constituents of the concrete mixture can become free of the frictional forces that neighboring constituents exert. In order to promote this workability, the concept has arisen of adding a major proportion of water, which is called water of mobility. This excess water makes it possible to put all the constituents of the concrete mixture in suspension and to maintain a lubricating film between them.
The water of mobility, which is indispensible for pouring fluidic concrete, is nevertheless deleterious for the characteristics of the concrete.
In practical terms, the concrete mixture contains an excess of water, due to the water of mobility that is not combined with the cement. For example, in a concrete mixture having 350 kg/m.sup.2 of cement, where the requisite quantity of water is 90 l, a mixture with 205 l of water is generally made. In a closed formwork, the excess water partly evaporates at the surface, and the remainder of the excess water continues to be present in the concrete in a free state, in the form of fine particles, which migrate from one void to another through miniscule channels as a function of the stress of working of the concrete (from the compressed zone to the stretched zone--the hysteresis phenomenon in concrete).
The presence of the free water, whose state is a function of the temperature of the concrete composition: than 0.degree. C. or greater than 100.degree. C.; capability; and
Thus it is desirable to preserve the water of mobility during the pouring phase, but to eliminate the water of mobility as soon as possible thereafter, and preferably before the concrete cures.
From French Patent Reference FR A 787 657, a formwork is known that includes a fine metal sheet that assures a filtration of the water. The filter sheet is stretched over a grid of expanded metal, and acts as a drain, which presses against an outer formwork plate, in which openings have been formed for the evacuation of the water. It is understood that such formwork is of the recoverable type; the various filtration elements that are pressed against the outer wall make the formwork inappropriate, because of its cost and structure, for an application as a sacrificial formwork.
From British Patent Reference GB-A 2 180 877, a formwork is known that includes a wall which assures the filtration of the excess water. The wall can be made of various materials, such as veneer, plastic, woven materials, for example. The rigidity of the wall when the concrete is poured is assured by a panel against which the filtering wall presses directly, with passages formed in the panel for the evacuation of the water.
These filtration techniques have various disadvantages. First, they require a relatively cumbersome support structure because the filtering wall is not self-supporting and must press against an outer wall that has evacuation openings. Second, assuming the formwork is partially sacrificial, or in other words that the filtering wall need not be recovered after the formwork is removed, but is intended to be part of the body of the concrete wall after the concrete has set, as may be the case if it is made of an insulating material (see British Patent Reference GB-A 2 180 877), the filtering wall necessarily forms an outer lining. The filtering w
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patent: 2175895 (1939-10-01), Hybinette
patent: 2496616 (1950-02-01), Barton
patent: 3376681 (1968-04-01), Demaison
patent: 3559355 (1971-02-01), Day, Jr.
patent: 5078940 (1992-01-01), Sayles
Dauron Fran.cedilla.oise
Durand Philippe
Friedman Carl D.
Wilkens Kevin D.
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