Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention is concerned with improvements in or
relating to refractory compositions of the kind comprising a
hydraulic cement and an aggregate.
In the manufacture of refractory compositions there
is used as aggregate, or there is used in the refractory compo-
sition, various materials in order to obtain or improve the
heat-resistance, and particularly fire-resistance and/or
resistance to ~emperature changes of the refractory compositions.
For the purpose of improving these properties it is customary
to use, e.g. asbestos ~ibre, mineral wool, glass wool, pearlites,
vermiculites, fragmented pumice stone, re~ractory clay, powdered
refractory clay, slagsand, quart sand, sintered corundum,
sintered dolomite, alumina, powdered dolomite, gypsum. However,
these materials fulfill the above listed requirements only in
part, or only imperfectly, or they raise problems in the produc-
tion or processability of the materials. In addition, some of
these materials are expensive or scarce, and others, such as
asbestos, present considerable health risks which make their
use undesirable.
According to this invention there is provided a
refractory composition comprising an aggregate, from 7 to 20%
by weight of hydraulic cement, and as a filler material, from
20 to 50% by weight of~silicon dioxide, o which at least 82~
is amorphous, not more than 18~ being crystalline quartz, which
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25 ~ has a bulk weight within the range of 0.25 to 0.50 gram per
millilitre, and of which at least 95% has a grain size below
50 microns.
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The term "aygregate" is used herein to include mineral
materials commonly mixed with cement in the manufacture of,
for example, concrete, but does not include said silicon dioxide
filler material.
The content of said silLcon dioxide is most advan-
tageously between 20 and 30% by we:ight.
The refractory composit:ion itself may be utilised in
the manufacture of a material requLred to have high fire and/or
heat resistance, such as in the manufacture of refractory bricks,
or refractory concrete. Alternatively, the refractory composi-
tion may be utilised in improving the fire and/or heat resistance
of an article, by being sprayed onto the articleO
Thus this invention also provides a method of improv-
ing the fire and/or heat resistance of an article, the method
comprising the step of applying to the article a coating of a
refractory composition in accordance with this invention.
It has been found that not only does a refractory
composition in accordance with this invention exhibit signifi-
cantly improved fire and/or heat resistance, but additionally
improves other physical properties when used in the manufacture
of various articles. This allows the refractory composition
in accordance with this invention to be used in the manufacture
of a variety of articles, improving not only the fire and/or
heat resistance of the article, but also improving other
qualitiesj su¢h as the sound absorbancy thereof.
Thus, this invention also provides a refractory
composition suitable for imparting fire, flame and heat resist-
;~ ~ ance to matexial,, such as concrete or refractory bricks,
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chipboard, concrete s]abs, ~ire-retarding panels, sound proofing
panels, moulded plas-tics panels, corrosion resistant panels,
refractory materials, heat insulating materials, electrical
insulation materials, sound insulation materials, ~efractory
moulding sand, emery paste, in which the refractory composition
is incorporated in or applied to the material, the composition
comprising an aggregate, from 7 to 20% by weight of a hydraulic
cement, and, as a filler material, from 20 to 50% by weight
of silicon dioxide, of which at least 82% is amorphous, not more
than 18% being cristalline quartz, which has a bulk weight within
the range of 0.25 to 0.50 gram per millilitre,.and of which at
least 95~ has a grain size below 50 microns.
Conveniently, the filler material is obtained as a
by-product produced in the electro-thermic production of ferro-
silicon and/or silicon, such as an electro-thermic pxocess
operating within a temperature of 1500 to 3000C. The basic
constituent of this substance is a fine, dust-like x-ray
am~rphous SiO2 (approximately 82 to 95%) some at least of which
may have been produced by direct submilation from the vapour
to the solid phase, with a small amount of crystalline quartz
(approximately 5 to 18%). X-ray examination has shown that.with
the exception of the comparatively small quartz content this
: dust or powder may be classified as being x-ray amorphous. In
~ addition, the ~iller material may contain small amounts of
.~ 25 oxides of.iron and/or calcium and magnesiuml and carbon.
The i.ncorporation of the silicon dioxide as a filler
material in a refractory composition according to this invention
not only contributes substantially to an improvement in the
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hea-t res.istance, particular'y fire resis~nce of -the refractor~
composition, but surpr:ising:Ly contribute~ c;ubstan-tially to an
improvement in other physical properties, such as mechanical
abrasion strength, resistance to temperature changes, thermal
insulation, sound insulation, elect.rical insulation properties
and improvements in the workability of masses, compositions or
mixtures, in particular building mixtures~
In particular, a refractory composition according to
this invention is well suited for u.se as or in a fire-inhibiting
or fire-resistant material or mass, in particular a mixture or
composition capable of being sprayed or tamped down for building
purposes.
Fire-inhibiting refractory materials, which according
to current custom and knowledge in the art consist of a mixture
of cement and asbestos fibres~ are, for example, sprayed on steel
girders to protect these against the action of fireO Whilst
these convention refractory materials certainly ensure the
- required fire protection, they are nevertheless very expensive.
Thus, by the use of this invention, a refractory
composition having better fire protection may be obtained in a
lçss expensive manner. Such a material has a high thermal
insulation value which is, at least partly, due to the low
density of the filler material, and over and above this it also
has great resista~ce to mechanical abrasion.
It is possible to improve or to further improve
certain other properties of the refractory composition by adding
other materials, either by utilising such other materials as
aggregate~ or by including such other materials in the composi~
tion in conjunction with the aggregate. For example, the
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thermal insulation value thereof may be improved by the use of
glass- or mineral- wool waste. Conveniently such materials
are obtained from the by products or waste materials produced
in the manufacture of insulation matting.
It is also possible to improve the adhesion properties
and the strength/density ratiol by utilising, in the preparation
of the refractory composition, wet1ing and/or flocculating agents
and/or materials of a similar kind.
Where the filler material is in the form the dust-like
products emitted in the electro-thermic manufacture o~ ferro-
silicon, chemical and physical reactions with t~e other
components of the refractory compositions are considerably
. enhanced and shrinkage, with resulting crack formation under
heat, is minimised, the filler material having the effect of . .
improving the thermal characteristics of the refractory composi-
tion with increasing temperature exposure.
It is also possible to include further additives wi~h
fire-inhibiting properties, such as calcium sulphate, advanta-
geously in the form of waste products occurring in the desulphuri-
zation of flue or smoke gases and containing predominantly or
e~clusively CaSO~.
The refractory composition according to this invention
~ may be used in the preparation of a sprayable or a tampable
: mass for use in the building industry generally, particularly
in pre-stressed concrete buildings, for insulating and protecting
~ steel girders. ';uch material may also be used in, e.g. steel-
: works, coke-ovens and foundries.
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Example I
A refractory composition according to this invention
was experimentally tested. For this purpose a sectional steel
girder (profile HEB 220), 3.600 mm long with foot plates welded
to top and bottom thereof was subj~ected to a load of 133 t~
after a protective layer had been applied to the girder of a
fire-proofing refractory composition, comprising mineral wool,
as aggregate, portland cement and the silicon dioxide filler
material, according to the in~ention, in a layer which was 23 mm
thick, and the qirder was then exposed, over a length of
3.100 mm, to ~emperatures rising from 8C to approximately 980C
in the course of 1.5 hours. The girder showed no reduction in
its load bearing capacity. The protective layer shrank in the
course of the testing time to an average thickness of 16 mm.
Comparative tests were carried out with commercially
available conventional asbestos-bearing spray-materials. For
achieving fire protection corresponding to class F 90, it was
necessary to use 10 kg/m of the conventional refractory composi-
tion containing asbestos, but only 7 kg~m2 were required with
the same result of the refractory composition according to this
invention. Specifically, the refractory composition in accord-
ance with this inventin which was used contained by weight
approximately 60% mineral wool, 20% cementl and 20% of the
silicon dioxide filler material. The mixture was prepared with
25 kg dry substance for 15 1. of water, with 75 ml of Lensodel
Registered Trade Uark), a tenside based on ethyleneoxide
condensates, inc:Luded in the mixture. The layer thickness
required to meet the demands of fire protection class F 90 for
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a material containing by weight approximately 60~ mineral wool,
20% pearlite and 20% hydraulic cement was approximately 60 mm.
Using the refractory composition according to this invention
and of the above specified composition only approximately 5 mm
layer-thickness was nQeded, but because such thin layers cannot
be very evenly applied it was found necessary in actual practice
to apply a layer thickness of approximately 15 mm. The consti-
tuents of the above mentioned refractory compo~ition may be
varied within very wide limits depending on the mechanical and
1~ thermal demands and it is also possible to add further conven-
tional materials to the mixture, such as, e.g. pearlites which
have good heat insulation properties.
Another field of application of this invention is
the manufacture of building panels. It is common practice to
produce (for example) ceiling panels, partition walls, doors
etc. from composition material panels, wherein the basic material
may be a chipboard or hardboard material, sprayed with the fire-
- proofing materials or mixtures. However, this type of production
is rather expensive. The same also applies to panels or slabs
made of concrete, gypsum or the like if these are to be fire-
proofed.
However, by the use of this invention, h~at resistance
and particularly fire resistance of such building panels is
substantially improved if the above described re~ractory
~ composition is used in a basic mixture for building panels,
particu1arly concrete slabs or panels and chipboard paneis,
or subsequently s~prayed onto the article.
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Advantageously such a panel may con~ist of a flarne-
proof fabric of plastic or wire xeinforced with a sealing layer
of paper or thin plastics ~oil, ~nd a layering on one or both
sides thereof of the above mentioned refractory composition.
This provides a considerable simplification in the manufacture
of building panels because, e.g. the wire mesh, which is
reinforcingly sealed, may be drawn continuously off a roll to
be subsequently rolled, sprayed or tamped on one or both sides
thereof with the refractory composition. Again the precise
ingredients of the refractory composition may be varied to suit
mechanical and thermal demands.
It is also possible to construct a building panel,
and especially a fire-yroof panel or mat in such a way that it
comprises an inner core of compressed mineral and/or glass wool
and an adhesive and protective layer of the refractory composi-
tion according to this inven~ion, the aggregate comprising
granulated or powdered stone.
Advantageously the refractory composition according
to this invention may be used to provide protective coatings
for refractory bricks~
- This invention is also suitable for making refractory
compositions in the form of fire-proof concret~, which is
particularly in demand for high-rise buildings. For achieving
economical production without loss of strength in ~he concrete,
the silicon dioxide filler material may be admixed with conven-
tional ingredients of concrete. By an appropriate addition of
the silicon dioxide filler material, it is possible to attain
fire-protection safety factors of, for example Class F 90,
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Class F 120 or even Class F 240. The amount of silicon dioxide
filler material in the concrete i~ preferably between 20 and
30% by weight. The concrete may c~lc;o contain further heat-
resistant additives including mineral wool. In conventional
concretes intended for exposure to very high temperatures,
Portland cement is less suitable as hydraulic binding agent, and
special binding agents which have so far been commonly employed
for the manufacture of fire-proof concrete have been required.
However by the use of this invention it is not necessary to use
special binding agents, and hydraulic cement may be retained
as a binding agent. Experiments have shown that the concrete
according to this invention may withstand a temperature of
approximately 1200C for several hours~
The refractory composition in accordance with this
invention may further he employed with great advanta~e in
making refractory bricks and high temperature~ resistant linings
for industrial furnaces and for the metallurgical industries.
Conventional tamping masses may be mixed with the silicon
dioxide filler material in amounts up to approximatel~ 35% by
weight and conventional spray masses up to approximately 50~ by
weightO These masses show a low degree of potential shrinkage
and a low starting point for sinter reaction, but a high degree
of fire resistance, strong adhesion to their background~ high
surface hardness and good elasticity. For example, a refractory
composition comprising (b~ weight) 30 % refractory clay (grain -
size 80% b~tween 0 and 0.5 mm), 30% sand (0 to 0.5 mm) 10
alumina flux cement and 30~ of the silicon dioxide filler
material, to which 20~ ~y weight of water is added, is extremely
suitable for spray application in repair work to the interior
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lining of coke oven~. In coke ovens, owing to the high tempera-
ture gradient of approximately 800C in the vicinity of the door
up to about 1,200~C in the middle of the firing chamber, it has
hitherto been necessary to employ several differently constituted
repair mixtures which were ad~pted to these different temperature
zones. ~Iowever, the above speciied refractory composition may
be successfully used in evexy region of the coke oven walls.
After the mixture has been sprayed on, it may provide a substan-
tially completely fissure-free coating which adheres irmly to
the wall and shows very good mechanical strength and durability.
A special ad~antage arises from the ~act that when
the refractory material according to this invention is used as/or
in refractory andhigh temperature resistant materials it is no
longer ne'cessary to add alkaliesO Previously conventional
refractory and high temperature resistant masses have required
an addition of alkalies, i.e. sodium silicate, to ensure adequate
adhesion of the mass to the refra~tory bricks. However, this
means that one has to accept a lower mollification point and
damags to the bricks.
Example II
A tamping mass for use in the repair of coke oven
doors may by the use o~ this invention comprises by weight 15%
sand (0 - 0.5 mm), 50% chamotte B (0-~ mm), 15% alumina cement
and 20% o~ the silicon dioxide fillar material. Such a tamping~-
mass has a~temperature resistance of 1,100C.Example I~I
A tamping mass suitable for use in foundries comprises
by weight 66% sand ~granulation 0 to 0.4 mm), 5% chamotte A,
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7% Portland cement 450 and 22% of silicon dioxide filler material.
This tamping mass has temperature resistance up to 1,550C.
In all of the above mentioned cases, where control
tests were carried out using extremely finely ground crystalline
silicon dioxide, it was found impossible to obtain similarly
good results to those achieved when using the refractory composi-
tion of this inventioncomprising predominantly amorphous, dust-
like silicon dioxide.
All percentages gi~en in the disclosure refer to
percentages by weight.
No claim is made herein to compositions which include
a substantial ~uantity of sodium silicate.
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