Process for manufacturing natural stone-type, panel-shaped construction and decoration materials

The invention concerns a process for manufacturing natural stone-type panel-shaped construction and decoration materials of high strength for facing facades, walls and floors in indoor and outdoor areas, consisting of stacked individual layers of crushed glass, charge materials, in particular sand, and mixtures thereof.

BACKGROUND OF THE INVENTION 
The invention concerns a process for manufacturing natural stone-type, 
panel-shaped construction and decoration materials of high solidity for 
facing facades, walls and floors in indoor and outdoor areas, comprising 
stacked individual layers of crushed glass, charge material, in particular 
sand, and mixtures thereof. 
A great variety of natural and synthetic materials are used for decorative 
applications in indoor and outdoor areas. Of the natural materials, in 
particular marble and granite find broad application and are used in large 
quantities for the interior and exterior facing of representative 
buildings. In addition to the decorative impression, corrosion resistance 
and economic production of the materials must also be ensured. Materials 
which occur naturally do not always meet these requirements, since 
sufficiently large surfaces of homogenous appearance can often not be 
obtained and since the corrosion resistance and solidity are not always 
optimal, due to the porosity of the natural material. 
A glass ceramic material is thus known from DE 41 25 698 C1, having the 
following composition (in wt. % on oxide basis): 
______________________________________ 
SiO.sub.2 
64.1-72 
Al.sub.2 O.sub.3 
2.9-11 
CaO 15.0-26 
MgO 0-8 
ZnO 0.ltoreq.2 
BaO 0-0.5 
K.sub.2 O 
0-7.4 
Na.sub.2 O 
0-2 
F 0.5-4 
______________________________________ 
whereby .SIGMA. Na.sub.2 O+K.sub.2 O is at least 2. 
This material is used in the construction industry as a natural stone 
substitute for decorative applications, to cover floors and to face walls 
and facades. 
Glass ceramic as a natural stone substitute offers a good decorative 
appearance, but is costly and difficult to produce, due to, e.g., the 
expensive ceramization process. In addition, relatively pure and thus 
valuable raw materials are needed to manufacture this material. 
DE 41 23 581 A1 discloses a process for manufacturing form bodies, in 
particular construction panels, from glass granulates, wherein raw 
granular material is made from a mixture of crushed glass and a foaming 
agent and said raw granular material can be expanded under heat, whereby 
first, a layer of unexpanded raw granules and, thereabove, a layer of 
expanded foam glass granules are deposited in a mold in a hot or cold 
state as feed, 
the feed is then heated to 700.degree. to 900.degree. C., preferably 
800.degree. to 900.degree. C. 
and subsequently compressed under a pressure of 0.005 to 0.015N/mm.sup.2 by 
5 to 15%, whereby a form body of firm compound arrangement is created. 
These construction panels manufactured by the process according to the DE 
41 23 581 A1 are particularly suited for use as insulation panels in a 
thermal insulation compound system, whereby the raw granular material of 
which the panels are composed must first be manufactured with great 
expenditure of energy. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a process for 
manufacturing decorative, natural stonetype, weather-resistant 
panel-shaped construction materials, including large-dimensional ones, 
which are resistant to acidic and alkaline media, whereby it is possible 
to produce, economically and in an environmentally beneficial manner, 
without the need of the use of organic additives, facing panels for 
facades, walls and floors, which meet all construction law and official 
requirements and, in addition, fulfill aesthetic and modern design 
requirements while permitting flexible design, from inexpensive and 
readily available raw materials such as glass, used glass and, e.g., sand 
and other natural inorganic charge materials. 
Furthermore, another object of the present invention is to select the 
manufacturing parameters in such a manner that the proposed method and a 
suitable temperature curve in the production of the construction materials 
ensure that 
the panels do not react with the production mold, 
no unevennesses occur on the panel surface, 
the panels are not subject to deformation, 
no bubbles, pores, occlusions and/or microcracks are formed in the top 
layer and 
there is no need for grinding or polishing of the final product. 
Upon further study of the specification and appended claims, further 
objects and advantages of this invention will become apparent to those 
skilled in the art. 
These objects are achieved according to the invention by process 
comprising: 
1.1 optionally depositing a level, evenly thick layer of sand in at least 
one temperature-resistant mold; 
1.2 deposition of a level, evenly thick layer of a mixture of crushed glass 
and sand on top of said layer of sand if the latter is present; 
1.3 super-deposition of a further level layer of crushed glass; 
1.4 whereby each individual layer is compressed and the entire resultant 
layer stack is compressed; 
1.5 subsequently heating the layer stack in the at least one mold to a 
temperature of 600.degree.-850.degree. C. during a period of 20-100 min.; 
1.6 tempering the heated layer stack at 600.degree.-850.degree. C. for a 
period of 6-35 min.; 
1.7 subsequently further heating the layer stack to a temperature at which 
the surface of the glass displays a viscosity .eta. of 10.sup.4 to 
10.sup.5.5 dPas and maintaining this temperature for 6-40 min., whereby 
the temperature application occurs unilaterally from above by a heat flow 
evenly distributed across the panel surface; 
1.8 cooling the layer stack to a temperature of 600.degree.-750.degree. C. 
over a period of time sufficient to obtain an even temperature 
distribution through the volume of the layer stack; and 
1.9 maintaining the temperature of 600.degree.-750.degree. C. for 15-65 
min., followed by precise linear cooling to a temperature of 
400.degree.-500.degree. C. at 2-5K/min. and, upon reaching this 
temperature, performing free or forced cooling to room temperature. 
In accordance with the inventive process, a layer stack composed of the 
stacked individual layers compressed in the temperature-resistant molds is 
provided and then subjected to a thermal treatment procedure comprising 
several successive treatments: 
Treatment 1.5: 
In this treatment, the layer stack is heated from room temperature to an 
annealing or tempering temperature at a rate whereby the panels are not 
deformed and/or unevenness does not occur in the panel surface. 
The layer stack is heated to a temperature of preferably about 
600.degree.-850.degree. C. The respective temperature level depends on the 
chemical composition of the charge material and the type of glass 
granulate used for the surface layer. The time period for heating the 
layer stack from, for example, room temperature to a temperature of 
600.degree.-850.degree. C. is preferably approximately 30 min. for panels 
having a volume of about 10-12 mm and preferably up to about 100 min. for 
panels having a volume of up to about 40 mm. For layer stack volumes from 
13 mm upwards, the treating period for the panel in the individual process 
steps rises in accordance with the formula t=0.08.times.D.times.t.sub.0, 
wherein D is the volume of the panel (in mm) and t.sub.0 is the heating 
period for a panel having a volume of 10 to 12 mm, i.e., about 30 minutes. 
Thus, for example, the heating period for a layer stack of 30 mm volume is 
preferably about: t=0.08.times.30.times.30=72 min. 
The heating area, preferably consisting of one or two heating chambers, is 
preferably arranged so as to ensure that the distribution of the heat flow 
proceeds parabolically in relation to the longitudinal and the transverse 
axis of the panel. This facilitates compensation of the heat losses at the 
edges of the panel and thus provides for an even temperature of the whole 
panel surface with a tolerance of preferably about .+-.10K to .+-.12K. If 
the temperature differences on the panel surface are larger than .+-.12K, 
the panel becomes uneven, because the differences of the temperatures of 
the individual layers of the panel, particularly in the vicinity of the 
edges, become too great. This error cannot be corrected during subsequent 
thermal treatment. This concerns particularly the corners of the panel. 
Treatment 1.6: 
The layer stack is kept at this temperature. The dwell period is preferably 
about 6-35 min., depending on the volume of the panel. Typically, a layer 
stack having a volume of 10-12 mm is tempered for preferably about 10 min. 
The curve of the heat flow distribution should be similar to that 
specified for treatment 1.5, but the temperature differences on the panel 
surface now preferably do not exceed 3-5K. If the temperature differences 
are greater, the panel edges and the volume of the melted layer on the 
edges become uneven, so that parts of the edge must be cut off to meet 
quality requirements. Treatment 1.6 is very important for the production 
of a high-quality surface layer. In this treatment, the formation of a 
temperature gradient, e.g., about 50-70K in the direction of the panel 
volume (10-12 mm) must be ensured, so as to avoid caking of the bottom 
side of the panel with the mold during the next thermal treatment. The 
temperature during treatment 1.6 must be maintained for a period 
sufficient to achieve a stationary thermal state. The dwell period or 
thermal retardation period is determined by the thermophysical properties 
of the layer stack and the temperature-resistant mold. If the mold is made 
of a material with low heat capacity and high heat conductivity, the 
retardation period is relatively short, because the desired thermal 
equilibrium is achieved swiftly. 
Treatment 1.7: 
In this treatment, the layer stack is maintained at an annealing 
temperature for a sufficient time to achieve a viscosity of 10.sup.4.0 
-10.sup.5 dPas. 
The layer stack is further heated to up to a maximum process temperature. 
In this treatment, a "temperature shock" is being applied with the 
objective of vitrifying the surface of the stack, but not the whole stack. 
The maximum process temperature is applied to the entire surface of the 
panel very evenly, and maintained until a viscosity of preferably about 
10.sup.4.5 -10.sup.5 dPas is achieved for the top layer. The treatment 
period is preferably about 6-40 min., in particular 12 min., for a layer 
stack of 10-12 mm volume. 
The treatment period or retardation period must also be sufficiently long 
for the generation of a mirror-flush, even surface on the entire panel. 
The temperature is applied unilaterally from above by a heat flow evenly 
distributed over the entire panel surface, preferably in a continuous 
furnace with continuous or phase operation. 
The determination of the maximum process temperature for charges of 
differential composition is particularly important. If the temperature 
selected is too high, the viscosity gets too low and errors are generated 
on the surface of the panel due to excessive degassing of the lower 
material layers. If the temperature selected is too low, the optimal 
mechanical properties are not achieved. The same negative effect occurs if 
the maximum process temperature is applied for too short a period. The 
evenness of the temperature distribution on the entire panel surface 
during this process step also has a decisive impact on the reproducibility 
of the colors. The temperature differences on the surface preferably do 
not exceed .+-.8K. The maximum temperature depends on the composition of 
the charge and is typically, e.g., 840.degree.-990.degree. C. It is 
determined for the individual compositions on the basis of the homogeneity 
of the surface layer. 
Treatment 1.8: 
The layer stack is cooled to a temperature of preferably about 
600.degree.-750.degree. C. during a time span sufficient to achieve an 
even temperature distribution through the entire volume of the stack, 
i.e., preferably a time period of about 6-35 min., particularly 10 min., 
for a layer stack having a volume of 10-12 mm. Preferably, the temperature 
is approximately equal to the temperature of treatment 1.6 or up to about 
25.degree. C. higher. Cooling is effected most simply by moving the mold 
through a passive zone, e.g., a chamber without a heating device of uneven 
lining, at a suitable speed. Here, uneven lining refers to insulation 
material having a thickness which varies along the direction of movement 
of the mold. The lining must thereby be formed in such a manner that the 
surface of the panel is evenly cooled. If this is not the case, residual 
stress and subsequent deformation of the panel result, which cannot be 
corrected by subsequent thermal treatment. The duration of the cooling 
period is determined, first of all, by the thermal capacity of the panel, 
the mold and the chamber, but also by the speed at which the mold is 
passed through this passive zone. 
Treatment 1.9: 
In this treatment, the layer stack is cooled from the maximum process 
temperature to room temperature at a rate whereby cracks and deformations 
in the layer stack are avoided. 
To temper the panels free of stress, the temperature is equalized in the 
entire volume. A tempering time period of preferably about 15-65 min. is 
usually sufficient, in particular 20 min., for a layer stack having a 
volume of 10-12 mm. More than 90% of the residual stress is thereby 
removed during the first 5 min. The evenness of the temperature 
distribution should preferably be equal to that of treatment 1.6. It has 
been found that an unevenness of the temperature distribution on the order 
of .+-.10K results in visible unevenness of the panel. The optimal 
annealing temperature corresponds to a viscosity of preferably about 
10.sup.13 -10.sup.13.5 dPas. 
Subsequently, cooling continues. Until a temperature of about 
400.degree.-500.degree. C. is achieved, the cooling speed is preferably 
about 2-5K/min., which results in a cooling period of about 40 min.-2 
hours. The cooling speed is determined by the volume of the panel, the 
thermal capacity of the entire panel, the mold and the mold shell. 
A higher cooling speed has a negative effect on the mechanical properties 
of the surface layer, resulting in cracks and deformations. A lower 
cooling speed has no effect on the quality of the panel. The following 
cooling speeds were found to be optimal: 3K/min. for panels with a volume 
of more than 15 mm and reinforced panels, and about 4-5K/min. for panels 
with a volume of 8-12 mm. If the cooling process is effected with a 
nonlinear temperature curve, micro-cracks form in the surface layer. 
Further cooling to room temperature takes about 3-3.5 hours and up to 
around 4.5 hours for very thick panels. It was found that, by using an 
active air cooling system or a cooled furnace roof, these periods can be 
reduced to about 1.5-2 hours, without any negative effect on panel 
quality. The performance of this step depends on the layout of the furnace 
and the organization of the operation. Panels have also been directly 
removed from the furnace at temperatures of 300.degree.-350.degree. C. 
According to the invention, a glass granulate of sheet glass and/or blown 
glass, e.g., from bottles and containers, and mixtures thereof can be used 
as crushed glass, whereby used and recycled glass as well as glass 
residues can be included. 
Preferably, the glass used has a composition within the following parameter 
ranges (in wt. % on oxide basis): 
______________________________________ 
SiO.sub.2 
60-80 
Al.sub.2 O.sub.3 
0-7 
Na.sub.2 O 
2-17 
K.sub.2 O 
0-7 
MgO 0-4.5 
CaO 0-10 
PbO 0-20 
BaO 0-13.5 
B.sub.2 O.sub.3 
0-15 
SrO 0-1.5 
ZnO 0-1 
ZrO.sub.2 
0-3 
TiO.sub.2 
0-1 
CeO.sub.2 
0-0.5 
Sb.sub.2 O.sub.3 
0-1 
F 0-5 
______________________________________ 
and a particle size of about 0.2-5 mm, in particular 2-3 mm, and a humidity 
content of .gtoreq.5%. 
The glass granulate should preferably have a particle size of 2-3 mm. It 
was found in experiments that a larger or smaller particle size may lead 
to deterioration of the mechanical properties of the panel. If the 
particles are too small, cavities and pores develop. If panels having a 
smooth rear side surface are produced, for which purpose very small 
temperature gradients are required across the entire volume of the stack, 
a glass granulate of minimal particle size is preferably used, which 
ensures a monolithic structure of the panel. No glass fibers may be 
contained in the glass granulate. The humidity of the glass granulate 
before the latter is mixed with sand is preferably no less than about 5%. 
If dry glass granulate is used, water must be added. 
In a preferred embodiment, any type of sand, with no requirement as to 
purity, with a particle size of &lt; about 1 mm is used as the charge 
material. 
The ratio of glass to sand is preferably about 3:1 to 6:1 weight parts, 
especially about 4:1. The proportion of sand in the mixture depends on the 
requirements regarding the rear side of the panel, whereby a minimal sand 
content is needed for panels having a smooth surface. It depends further 
on the nature of the decorative surface layer and the parameters of the 
thermal treatment. It is very important that the mixture is homogenous in 
its entire volume. 
In the process according to the invention, the charge material is selected 
so that the viscosity .eta. of the glass used is always lower than the 
viscosity of the charge materials. 
This is important with regard to the natural stonetype appearance, thus to 
the distribution of the glass phase in the construction panel, and also 
with respect to the strength properties. 
Preferably, the charge material is sand having a particle size of less than 
1 mm and a moisture content of at least 5% water. 
The stacked individual layers are thereby filled into the mold in layer 
depths of preferably: 
0-30 mm, in particular 1.5-2 mm for the sand layer (1.1, i.e., the first 
layer); 
2-30 mm, in particular 12-15 mm for the mixture layer (1.2, i.e., the 
middle layer); 
2-7 mm, in particular 3-5 mm for the glass layer (1.3, i.e., the upper or 
surface layer). 
The base of the mold is covered with, for example, a sand layer of about 2 
mm high. This layer is covered by the mixture of glass granulate and sand. 
The height of this layer is, e.g., 12-15 mm. When manufacturing reinforced 
panels, a metal reinforcement means such as a wire netting or grating is 
laid into the center of this layer. 
It has also been found that, for certain panel applications, it can be 
technically advantageous to insert glass and/or ceramic fibers in middle 
layer 1.2. Care must, however, be taken to ensure that the fibers are not 
longer than the maximum diameter of the particle size used. Fibers which 
are too long cause considerable strength losses. 
Then the charge is compressed and its surface leveled. The use of vibration 
tables is advantageous. After compression, the layer of colored glass 
granulate is deposited, for example, at a thickness of 3 to 5 mm, and the 
surface is leveled again. The glass granulate mixtures for the decorative 
surface layer should be standardized for each color shade and produced for 
storage. A change in the composition of this mixture, e.g., when using 
crushed glass of unknown origin and chemical composition, necessarily 
entails an adjustment of the process parameters. The glass granulate for 
the decorative surface layer can be deposited through different molds or 
sieves, e.g., to produce specific patterns. 
In a preferred embodiment according to the present invention, mica and/or 
color pigments and/or coloring metal oxides are also mixed into top layer 
1.3 of crushed glass in parts of about 0.05-3 wt. %, relative to the total 
weight of the top layer, to obtain certain decorative effects and color 
shades. By admixing mica, construction panels are, e.g., produced whose 
appearance is very similar to that of granite slabs. 
According to a particularly preferred modification of the process, the 
glass of the uppermost individual layer 1.3 is cooled to temperatures 
which correspond to viscosity values .eta. of about 10.sup.7 -10.sup.8 
dPas after treatment 1.7 during which the maximum process temperature is 
achieved. This lower temperature is then maintained for preferably about 
5-15 min., in particular 10 min., and subsequently cooled further to 
preferably about 300.degree.-350.degree. C. as swiftly as technically 
possible without excessive technical requirements, e.g., by means of cold 
compressed air. 
Optimal results were thereby obtained with panels of 10-12 mm volume. The 
strength of the surface layer is 5 to 8 times greater than that of 
ordinary panels. 
If micro-cracks developed during the cooling of the surface layer, these 
can be removed by tempering at a temperature of preferably about 
400.degree.-500.degree. C. If required, this tempering may be integrated 
as an additional technological step into the manufacturing process. 
The construction materials produced by the process in accordance with the 
invention typically display the following values: 
______________________________________ 
Density 2.5-3.0 g/cm.sup.3 
Bending strength 10-20 MPa 
Crushing strength 200-250 MPa 
Shock strength app. 8 kgcm/cm.sup.2 
Hardness cf. Mohs 6-7 
Moisture absorption 0.2%-0.8% in 48 hours 
Thermal expansion coefficient 
90-120 .times. 10.sup.-7 .times. K.sup.-1 
Quenching strength 60 K-120 K 
(Temperature difference) 
Resistance to frost (cycles 
min. 100 
from +30.degree. C. to -30.degree. C.) 
______________________________________ 
Without further elaboration, it is believed that one skilled in the art 
can, using the preceding description, utilize the present invention to its 
fullest extent. The following preferred specific embodiments are, 
therefore, to be construed as merely illustrative, and not limitative of 
the remainder of the disclosure in any way whatsoever. In the foregoing 
and in the following examples, all temperatures are set forth uncorrected 
in degrees Celsius and unless otherwise indicated, all parts and 
percentages are by weight. 
The entire disclosure of all applications, patents and publications, cited 
above and below, and of corresponding German application P 43 19 808.2, 
filed Jun. 15, 1993, are hereby incorporated by reference.

EXAMPLES 
The process for manufacturing the decorative, natural stone-type 
construction materials according to the invention is now described by 
reference to the following examples: 
Example 1 
The mold, e.g., measuring 800.times.600 mm, is cleaned of material residues 
such as sand, glass and refractory coatings before filling. After 
cleaning, a thin layer of refractory suspension (kaolimite, Al.sub.2 
O.sub.3.2SiO.sub.2.2H.sub.2 O) is applied to the walls and base as a 
separation aid and the corners are covered with a kaolin paste to prevent 
subsequent sticking, baking or sintering with the mixture. 
The mold is then dried, preferably with infrared emitters. 
The mold consists of conventional refractory or heat-resistant material. 
Cordierite, for example, such as that conventionally used in the ceramics 
industry as kiln furniture, is advantageously employed. 
The mold material must thereby be so selected that sintering ("baking") of 
the mold with the mixture does not occur at the process temperatures. 
The process is to be explained using the example of window glass having the 
following composition (in wt. %): 
______________________________________ 
SiO.sub.2 
71.7 
Al.sub.2 O.sub.3 
1.85 
Fe.sub.2 O.sub.3 
0.11 
CaO 6.8 
MgO 4.04 
Na.sub.2 O 
13.8 
K.sub.2 O 
1.3 
SO.sub.3 
0.4 
______________________________________ 
The glass is coarse-crushed by conventional means in a crusher into glass 
granulate having a grain size of .gtoreq.2 and .ltoreq.3 mm. The moisture 
content in accordance with the invention is obtained by admixture of 5% 
water. 
The admixture of water has the additional advantage that dust formation is 
prevented. 
The mold prepared as described above is now filled with sieved sand having 
a grain size of .ltoreq.1 mm and a moisture content of 7% in a layer 
volume of 1.5 mm. The sand is so distributed that it forms an evenly thick 
layer on the base of the mold and is simultaneously compressed. 
Then a homogenous mixture of 6 parts of the above-specified window-glass 
with 1 part sand is produced. The bottom sand layer in the mold is covered 
with this mixture in a layer of 12 mm volume, whereby vibration is 
continued to obtain a good compression of the layers. 
Apart from sand and glass, this central layer may also contain other 
industrial materials, such as slag, ash, waste materials from fiberglass 
production and other, in particular porous, inorganic materials. 
A layer of pure glass of 3 mm volume is subsequently deposited. 
Each layer itself and the entire layer stack are compressed. The mold thus 
filled is then brought into a continuous electrically heated furnace, and 
the layer stack is heated to a temperature at which the material sinters, 
whereby the surface of the layer stack melts to the point of forming a 
fire-polished, mirror-flush surface. 
The continuous furnace must thereby be controllable in such a manner that a 
very even temperature is generated across the surface of the mold resp. 
the material to be sintered and that a temperature gradient through the 
entire volume of the layer stack is ensured. 
A continuous furnace having a series of successive connected rectangular 
chambers forming independent and separately controllable subassemblies 
which can be separated from each other by spatial screens has proved 
particularly advantageous. 
The layer stack of 16.5 mm volume on the basis of window-glass is heated in 
the mold at 18K/min. to 750.degree. C. in 40 min. and annealed for 13 min. 
It is important to ensure that a temperature gradient in the direction of 
the panel volume is achieved in this temperature range so as to prevent 
sticking of the base of the panel to the mold at the maximum temperature. 
Then further heating with 10.degree. K./min. in 20 min. to 950.degree. C. 
is carried out and this temperature is maintained for 16 min. The 
viscosity of the window glass at 950.degree. C. is 10.sup.4.5 dPas. 
At this viscosity, the later surface quality of the panel can also be 
influenced: 
If a panel of wavelike surface is to be produced, the mold with the 
material, starting at this maximum temperature, is brought to such an 
oscillation that standing waves form on the melted surface. 
If the surface of the panel is later to display decorative micro-craters, 
the evolution of gases from the lower areas is induced at this temperature 
and the structure thus obtained is subsequently frozen by means of cooling 
with a rapid increase in viscosity. 
The cooling of the product thus sintered and partially molten to 
750.degree. C. then commences at a rate of 15K/min. for 13 min., whereby 
this temperature is then maintained for 27 to 30 min. The cooling must 
thereby occur in such a manner that an even temperature distribution 
throughout the entire volume of the stack is obtained. 
Then precise linear cooling at a rate of 3K/min. to 420.degree. C. followed 
by subsequent cooling to room temperature without parameters is performed. 
Example 2: 
To demonstrate the range of variation and universality of the process 
according to the invention, a relatively unusual glass composition was 
selected for this example (wt. %): 
______________________________________ 
SiO.sub.2 70 
Na.sub.2 O 16 
Al.sub.2 O.sub.3 
7 
CaO 2.5 
F 4.5 (!). 
______________________________________ 
The glass granulate was crushed and a grain size of 2 to 3 mm selected by 
sieving. 
Three layers, a to c, were again deposited in the mold: 
a) 1 mm sand, 
b) 8 mm mixture glass/sand with 4 parts glass to 1 part sand, 
c) 3 mm pure glass granulate. 
The temperature cycle for this glass type ("Marblite"): 
______________________________________ 
At In Ret. Pd. 
From (.degree.C.) 
To (.degree.C.) 
(.degree.K/min.) 
(min.) (min.) 
______________________________________ 
(1.5) room temp. 
650 21 30 -- 
(1.6) 650 650-680 -- -- 10 
(1.7) 680 920 9 27 12 
(1.8/9) 
920 690 23 10 20 
(1.9) 690 450 4 60 -- 
450 Room temperature with no qualification 
______________________________________ 
Ret. Pd. = retention period 
The examples provide very durable natural stone-type construction and 
decoration materials with a very long useful life. They can be used to 
face external and interior walls in industrial, residential and transport 
infrastructure properties, for furniture and for decorative works of art. 
The material is produced from sand and glass. It is characterized by high 
strength and solidity. It is hygienic, easy to clean, highly 
temperature-resilient and electrically non-conductive. 
The facing material according to the invention is a three-layered panel 
material. The lower layer is preferably mainly sintered sand. The central 
layer is partly molten by means of respective thermal treatment, so that a 
partially crystalline, glass-type material is obtained. The upper, 
decorative layer is preferably made of crushed glass with optionally other 
additives (colored metal oxides). This layer is fire-polished in the 
manufacturing process. With regard to its physical, chemical and 
mechanical properties, the construction and decoration material according 
to the invention is superior to natural and expensive materials such as 
granite, marble or travertine. 
The panels according to the invention are fastened, e.g., by a mounting 
system such as that presented in the EP 0 411 442 or by other currently 
used and commercially available arrangements. 
The preceding examples can be repeated with similar success by substituting 
the generically or specifically described reactants and/or operating 
conditions of this invention for those used in the preceding examples. 
From the foregoing description, one skilled in the art can easily ascertain 
the essential characteristics of this invention, and without departing 
from the spirit and scope thereof, can make various changes and 
modifications of the invention to adapt it to various usages and 
conditions.