Method of foaming a foamable composition in a sealed sack

The invention concerns a construction material, which is produced by pouring a foamable composition into a hermetically sealed sack consisting of thin sheets and causing foaming of the poured foamable composition, the hermetically sealed sack being elastically or plastically deformed by the pressure produced with the foaming of the foamable composition and held in a predetermined shape with the solidification of the foamable composition after the foaming thereof, and also a method of manufacturing the same construction material. The construction material is light in weight and has satisfactory mechanical strength and rigidity.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a construction material, which is large in size, 
has a panel-like shape and is used as roofing materials and wall 
materials, and a method of manufacturing the same. 
2. Description of the Prior Art 
Where heavy weight panels such as precast concrete panels are used as 
roofing materials on a large span frame or like structure where supports 
are spaced apart large distances, the panel and support members must have 
high mechanical strength and the mounting structure is complicated, thus 
leading to high cost. 
On the other hand, in case of light weight panels such as sandwich panels, 
their manufacture is complicated, leading to high cost. Besides, their 
durability, rigidity and reliability are inferior. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide a construction material, which has 
a large size and a panel-like shape and is used as roofing materials and 
wall materials, and also a method of manufacturing the same. 
Another object of the invention is to provide a construction material, 
which is light in weight, has high mechanical strength and rigidity and 
can be used as roofing materials for large span frames or structure to 
reduce load of support members. 
A further object of the invention is to provide a construction material, 
which is simple in construction and can be manufactured as a large-size 
panel even at the site of construction, and a method of manufacturing the 
same.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
The construction material according to the invention is featured in that it 
is produced by pouring a foamable composition into a hermetically sealed 
sack consisting of thin sheets and causing foaming of the foamable 
composition in the sack to cause the sack to be elastically or plastically 
deformed by the pressure of foaming and obtain a predetermined shape with 
the solidification of the composition after the foaming. 
The thin sheets that constitute the sack may be metal sheets, e.g., steel 
sheets, stainless steel sheets and aluminum sheets, or synthetic resin 
sheets, e.g., polyvinyl chloride resin sheets and polyethylene resin 
sheets, or fabrics coated with resins. They should not pass the 
non-solidified foamable composition through them and also should have 
flexibility. 
The hermetically sealed sack is formed by overlapping two thin sheets as 
mentioned above and securing together their edges, with or without a C 
shape steel frame or the like interposed between their edges, by means of 
welding, an adhesive or pressing them together with press dies. 
The composition to be poured into and foamed in the sack, should be one, 
which can have sufficient rigidity after its foaming and solidification. 
Particularly, it should be one which can produce a sufficient pressure of 
foaming to cause elastic or plastic deformation of the sack consisting of 
the thin sheets into a desired shape. Examples of the foamable composition 
that can be used are foamable polyurethane, foamable phenol resins, 
foamable urea resins, foamable polystyrene, foamable polyethylene and 
foamable cement mortar. 
FIG. 1 shows a construction material A according to the invention. It 
comprises a hermetically sealed sack, which is formed by overlapping two 
thin metal sheets 1 having the same square shape and welding together 
their edges, and a foamed composition 2 obtained as a result of foaming 
and solidification of a foamable composition poured into the sack. 
FIG. 2 shows an example of the set-up for fabricating the construction 
material A. To produce the material A, the sack, which is formed by 
overlapping two square metal sheets 1 and welding together their edges, is 
first held in position by securing its edges by clamps 3 to a stationary 
frame 4. The foamable composition is then poured into the sack and then 
foamed. As the foamable composition is foamed, the sack, which has its 
edges secured in position by the clamps 3, experiences a pressure of 
foaming of the composition. As a result, the two thin sheets constituting 
the sack are pushed outwards and elastically or plastically deformed into 
a spherical shape. Thus, with the construction material according to the 
invention, which is obtained after the foaming and solidification of the 
foamable material, the outer side of the thin sheets has a shell-like 
shape, and the tension in the thin sheets is in balance with the internal 
pressure. The material thus can maintain its shape after the stationary 
frame 4 is removed, and it has high rigidity and bending strength. 
FIG. 4 shows another construction material according to the invention. It 
is foamed by using a square frame 5 consisting of C shape steel as shown 
in FIG. 3. To be more specific, the edges of two thin sheets 1 are 
hermetically secured to the opposite sides of the frame 5 to form a sack. 
Then, the foamable composition is poured into the sack and then foamed and 
solidified. In this way, a construction material which includes the frame 
5 can be obtained. 
FIG. 5 shows a roof of a large span structure. It consists of a plurality 
of construction materials A provided in a side-by-side arrangement on top 
of a roof frame consisting of trusses 6. To produce this roof, a number of 
hermetically sealed sacks, each of which is formed by overlapping two 
square or right hexagonal thin steel sheets and welding together their 
edges, are arranged on top of the roof frame consisting of the trusses 6 
with their edges secured by clamps 7 to the trusses 6. The foamable 
composition is then poured into each sack, and then it is foamed and 
solidified, thereby causing deformation of the two thin sheets into the 
shape of a spherical shell. Thus, a roof which consists of a number of 
shell-like construction materials A arranged on top of the roof frame can 
be obtained. Alternatively, the construction materials A may be 
preliminarily formed, and then they may be secured in the side-by-side 
arrangement to the trusses 5 of the roof frame, thus obtaining the roof. 
The materials A may be secured either by continuous support or point 
support to the trusses 6. 
The construction material A may have other shapes than the square and 
hexagonal shapes, for instance circular and triangular shapes. Further, 
the sack may be formed by overlapping three or more thin sheets instead of 
two thin sheets. Furthermore, it may include a metal plate as a core 
member. 
FIG. 6 shows a further example of the construction material A according to 
the invention. In this material, a partition member 8 is provided between 
two thin sheets 1 to restrict the distance between the thin sheets 1 when 
the sheets are deformed. 
As a further example, it is possible to use two thin sheets having 
different moduli of elasticity and thus deformed differentially. In this 
case, a construction material having an asymmetric shape on the front and 
rear sides, can be obtained. 
As has been described in the foregoing, according to the invention a 
foamable composition is poured into a sack consisting of thin sheets and 
foamed in a hermetically sealed state to produce a construction material. 
Thus, it is possible to obtain a construction material having a desired 
shape and high rigidity. Particularly, sufficient mechanical strength can 
be provided with respect to load in the normal direction. Further, the 
material is light in weight because its inside is constituted by a foamed 
composition. Furthermore, since the construction material according to the 
invention can be formed by pouring a foamable composition into a sack, it 
is simple in construction and can be comparatively readily fabricated, and 
it is further suited for fabrication at the construction site.