Stock material or miscellaneous articles – Two dimensionally sectional layer – With frame – casing – or perimeter structure
Reexamination Certificate
1999-12-03
2001-11-20
Thomas, Alexander S. (Department: 1772)
Stock material or miscellaneous articles
Two dimensionally sectional layer
With frame, casing, or perimeter structure
C428S048000
Reexamination Certificate
active
06319579
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a settable mixture comprising magnesium oxide and magnesium chloride. The invention further relates to a method of manufacturing a sound insulating floor construction and to a sound insulating floor construction.
Mixtures of magnesium oxide and magnesium chloride, sometimes referred to as Sorel cement, are known in the art for application as binders for industrial floorings, for which purpose they are favored on account of high elasticity and bending tensile strength properties. It is also known in the art to manufacture lightweight building slabs comprising Sorel cement in combination with wood chippings.
2. Description of the Prior Art
International patent publication no. WO89/02422 discloses a settable magnesium cement composition comprising magnesium oxide, magnesium chloride and coarse fibrous long-stranded sawdust. In the composition suggested the content of magnesium chloride constitutes approximately one third of the content of magnesium oxide as measured by weight Suggested applications comprise use as a floor leveling compound or manufacture of moulded products such as tiles and the like. Particular advantages claimed with this composition comprise reduction of sweating, reduction of dust, better control over product quality, and sound attenuation among others.
German published patent application DE 41 08 562 suggests for a floor leveling compound a mixture of coarse wood chips with granulated foamed polystyrene together with ceramic aggregates and a hydraulic binder such as cement or plaster of Paris. The publication contains in respect of the ceramic aggregate also suggestions for expanded clay aggregate or pumice and others.
A publication “Lexikon der Technik” by Lueger, 1972, page 471 explains Sorel cement used for floor slabs. Filler materials, such as wood chips, paper, cork and stone powder, are mentioned. A solution of magnesium chloride is prepared to a density of 1.16 to 1.19.
A publication “Estriche und Bodenbeläge Im Hochbau” by Diplom-Ing. Friedrich Eichler, VEB Verlag Technik Berlin, 1955, discloses a floor slab cast of Sorel cement on top of an insulation mat. Margin strips are arranged on the walls so as to separate the floor slab from the walls. The publication mentions Sorel cement with fillers, such as wood chips and stone powder. According to this publication, the floor slab must have a thickness of at least 5 cm for reason of structural considerations.
Applicant has found that Sorel cement is highly prone to expansion during setting. Relative expansions in the order of 1% are very likely. Given this rate of expansion a floor slab may, depending on dimensions and boundary constraints, crack and break up. The expansion takes place slowly but keeps growing over an extended period of time. This makes the expansion difficult to monitor accurately during the early stages and means that a risk of self-destruction is there for a long period.
The expansion propensity practically limits the use of Sorel cement to applications as a binder, to products cast in molds or to floor leveling compounds laid in comparatively thin layers and adhered to a floor base, which serves to keep the Sorel cement layer in position.
The applicant has found that the admixing of wood fibres in any substantial amount tends to make the mixture sticky and viscous and hence difficult to mix properly and difficult to apply. Improper mixing is detrimental to the structural integrity of the hardened product and likely to aggravate expansion problems.
SUMMARY OF THE INVENTION
The invention, in a first aspect, provides a settable mixture of ingredients comprising quantities of ingredients as follows:
between 12 and 18% by weight of MgO,
between 12 and 18% by weight of MgCl
2
,
H
2
O in a quantity appropriate to produce together with the MgCl
2
ingredient a slurry of a density within the range of 1.16 to 1.20 g/cm
3
, and
balance up to 100% of resiliently compressible fibres and a filler material.
This mixture combines the advantageous effects of Sorel cement in high elasticity and bending tensile strength as well as sound attenuation in a material where the expansion propensity is a factor of ten lower than is the case in other Sorel cements. Expansion rates in the order of one per thousand are easily achieved, meaning that even large slabs may be cast without any problems. The mixture is easy in mixing and in application. The strength of the mixture when set is comparable to that of ordinary cements
This performance of the inventive mixture is believed to be attributable to a number of factors. The filler material serves to dilute the expansion propensity by replacing corresponding volumes of magnesium oxide and magnesium chloride. The resiliently compressible fibres are believed to restrain expansion while also being capable of absorbing expansion internally through compression.
Although a range of proportions between the ingredients may be used, it is believed that roughly equal portions by weight of MgCl
2
and MgO will further the formation of strong and stable crystal structures in the product when set.
According to a preferred embodiment, the resiliently compressible fibres comprise ligneous fibres such as wood chips or sawdust. These fibres are preferably finely grained in order that the liquid mixture will stay fluent until it sets.
According to a preferred embodiment, the filler material comprises an expanded material. The expanded material reduces the density of the compound and permits internal absorption or expansion, the spheres of the expanded material being capable of collapsing internally so as to relieve any pressure in the immediate surroundings. The spheres of the expanded material do not corrupt the fluency of the mixture.
According to a preferred embodiment, a part of the filler material comprises comminuted aggregate such as fine gravel or stone dust. These materials contribute to the excellent strength of the mixture when set.
The invention, in a second aspect, provides a method of manufacturing a sound insulating floor construction on top of a floor base and within confinement walls, comprising the steps of applying on top of the floor base a layer of soft, resilient mats, arranging along the confinement walls and at least partially above a top side of said layer of mats a spacer list comprising a soft, resilient material, pouring on top of said layer top side a mixture comprising magnesium oxide, magnesium chloride, water, resiliently compressible fibres and a filler material, said filler material comprising at least one ingredient selected from a group comprising an expanded material, expanded clay aggregate, expanded glass, expanded polymer and pumice, leveling the top surface of said mixture, and allowing said mixture to set to form a solid slab.
This method provides the manufacturing of a floor comprising a floating slab made of the inventive mixture. The floating arrangement of this slab by the soft resilient support under the bottom as well as along all sides decouples any body transmission of sound or vibration waves and hence achieves excellent sound insulation capabilities. The insulation properties are further enhanced by the inherent sound deadening features of the inventive mixture. The floor slab may be cast in situ even in very large formats.
Although this floor construction is generally applicable it is particularly favored in critical fields of application such as accommodations on ships where spaces are narrow and where the requirements to weight, sound insulation, vibration insulation and fire resistance are extreme.
The invention, in a third aspect, provides a sound insulating floor construction adapted for installation on top of a floor base and within confinement walls, comprising a layer of soft, resilient mats, arranged on top of the floor base, a spacer means adapted to maintain a spacing to the confinement walls, and a slab placed on top of said layer of mats, said slab having been formed by pouring on top of said layer of mats and within said spacer
Sika AG vorm. Kaspar Winkler & Co.
Thomas Alexander S.
Vigil Thomas R.
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