Note: Descriptions are shown in the official language in which they were submitted.
This lnven-t-ion rclates ~o a process for t:he production of foam
concrete blanks and in particular builcling brick blanks.
In the production of molded bodies from foam concrete a casting mixture
that contains the foam is produced and this is then filled into an open-top
mold from which the molded body so formed is removed after it has reached a
sufficient degree of firmness, and divided into the desired blocks; these are
then stored in air until they have reached their proper end hardness~ This
process demands a considerable amo~mt of mold time and is also costly insofar as
the division of the molded bodies that are produced in the mold into building
bricks or the like is connected with a corresponding wastage. Quite apart from
this, the longer mold times result in sedimentation effects, so that there is no
regular densit~ throughout the height of the molded bodies. ln addition, it is
impossible to produce air blocks in this manner; only solid blocks can be
produced The unprocessed densit~ cannot be ~ell controlledO
In addition, in the book b~ ~O Altner and W. Reichel entitled ~e~
Cement Hardening (Betonschnellerhaertung), Betonverlag GmbH, 1981~ Pages 196 to
206, the electro-thermal treatment of concrete is described, and there is also
some discussion of tests involving warming the concrete in a high frequency
field~ In this regard it is foreseen that the unprocessed mixture is heated
steadily to a maximum value within several minutes9 in order to achieve an
acceleration of the hardening process, and this is combined with a mechanical
effact, e.g., vibration, in order that any structural changes produced in the
already hardened concrete as a result of the rapid heating are reversed. How-
ever, this is not suitable for foam concrete, for which reason foam concrete
blanks are produced in the normal manner with a prestanding time of 3 - 5
hoursl ard then subjected to electro-thermal treatment in order to achieve the
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end hardness, this belng done with the use of lower heating rates. See page
206 of "Rapid Cement ~larclening". Prestanding times of this kind are, however,
usually achieved with a great expenditure of molds and frequently involve a
partial collapse of foam and no very sli~ht unprocessed densities can be
achieved
I~ is ~he task of this invention to create a process by means of
which foam concrete blanks can be produced simply and rapidly, these having an
adequate blank hardness and being, in the main, of a regular densityO
~or this reason, the invention relates to a process for the
production of foam concrete blanks, in which a pourable base mixture consisting
in the main of granular material, in particular containing silicate; water;
cement; and foam, in which regard the foam as such is added to the base
mixture or produced in the base mixture by means of a foaming agent, this base
mixture being placed in a mold, after which the blank, when it displays
sufficient hardness, is removed from the mold. In this regard it is arranged
that-
aO prior to being filled into the mold a temperature dependent
accelerating agent for hardenlng the base mixture is added to the base mixture;
b. the base mixture that is in the mold is heated homogenously to
a te~perature of approximately 40 - 80C, particularly 45 - 60C;
c, the heating of the base mixture in the mold is undertaken
rapidly enough that the expansion of the base mixture brought about by the
heating process is terminated before the cement hardening starts;
d, the blank is removed from the mold after a warming period of
approximately 20 - 120 seconds, but in particular 25 - 60 seconds.
After being removed from the mold the blanks can be hardened in the
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normal manner, that is to say by alr clry:ing, by hardening in steaml or by
autoclave hardenillg using super heated steam or by C02 hardening or also, if
necessary, by electro-thermal treatmen~.
It is expedient that the blanks are produced in a ~old that can be
closed against the egress of the base mi.xture~ this bei.ng filled with the base
mixture to the extent that the volume that remains corresponds to the
expansion tha~ is brought about by the heating process. After being removed
from the mold the blanks are, for all practical purposes, i.n their final shape
and there is no need for t`urther division of the larger blocks into building
bricksO As a result of this, and as a consequence of the short molding times
and of the rapi.d heating there isS for all practical purposes, a regular
~mprocessed density for the blanks or final bricks, respectively, and from
brick to brickO
The fact that the hea~ing o the ba.se mixture in the mold is
effected so rapidly and tha~ the expansion of the base mixture as a result of
the heating is ended substantially before the cement begins to harden, leads
to the elimination or at least reduction of the danger of cracks forming in
the blank, which normally ~akes place when a base mixture containing a foam is
heated as a result of the great expansion of the foam brought about by the
2~ increase in temperatureD Because of the cement hardening7 which in the main
occurs after the expansion, the structure of the blank when the foam is
expanded is fixed, which means ~hat the unprocessed density o the blank is
sim~ taneouslr reduced as a result of the expansion of the foam.
As a result of the use of closable molds it is possible to produce
slabs that are precisely dimensioned, which can, for example, be cemented to
each other4
Tlle use of lndividual molds for the production of the blanks and
the pourable cons.istency of the base mixture make it possible to produce air
blocks of foam concrete~ -these having an op~imal cavity confi~uration for heat
retention at a high cavity ratio, in which connection the holes in the blocks
can be configured. as blind holesO In adclition~ the process is suitable for the
producti.on of solid slabs at lower unprocessed densities which can fall to as
lo~ as 300 kg/m~, as well as air and solid bricks having integrated heat
retention. In this connecti.on a cavity ~hat extends in the main throughout
the width or length of the brick is filled with a heat retention material such
as a polystyrene b].ock, which is inserted into this cavity.
It is also possible to produce a brick having a denser outer layer -
for example, covering four sides, on two opposite sides, or only Oll one broad
side - if one places a suitable separator in the moldJ this dividing the mold.
The appropriate base mixtures of different unprocessed densities are then filled
into the separated sections of the mold, after which the separator is removed
and after the mold has been closed the mixture is heated. It is possible to
produce facing or veneer bricks in this wayO
The blanks achieve a degree o:E hardness suficient for removal from
the mold and subsequent transportation by the heat treatment that is und0rtaken
during the molding process; this leads not only to shorter cycling times during
the production of the blanks and, in the case of air blocks, the formation of
ribs with the desired lesser wall thickness with the necessary hardness ~blank
hardness of more than Ool M/mm ) but i~ also permits an economically acceptable
processing of a base mixture for foam concrete bricks. The time in the mold
and thus the cycle tlme are lowered with an increase in the accelerator
additive~ As a result of the practically pressure-free production of the blanks,
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the addition of foam to the base mixture is particularly effecti-ve, since for
all practical purposes the pores of the foam are not compressed during
production of the blanks and thus contribute fully to reducing the bulk shear
density of the bricks or molded bodies and thus to the achievement of good
heat retention properties. In acldition, it is also surprising that the pores
that result from the foam remain in the brick even tllough the foam itselE
posscsses only a slight stabillty at the end temperatures that are unforeseen
and the high heating rates for the base mixture in the mold, always providing
that this still exists at the temperatures that are used~
In place of the usually used quartz sand and/or quartz powder,
other materials can be used, for example, pumice, argillaceous earth, or flue
ash, tailings, or the like, which can replace the quart~ sand either completely
or in part, and if necessary can contribute to a certain reduction of weight
of the bricks that are produced~ In the case of autoclave hardening, however,
materials that contain silicates must be used, in which connection chalk can
also be added, this contributing additionall~ to the strengthO
As far as cement is concerned, use can be made of a portland cement
~hereas a hardening accelerator can be used as an accelerating additive for the
hardeningO This is activated by the intended increase iTl temperature, by the
2Q temperature of the base mixture prior to filling into the mold but is, however,
for all practical purposes, non-effective and thus temperature dependent, or
else is retarded by a hardening retardant prior to the heating of the base
mixtureO Alternatively, it is possible to use a quick hardening cement, the
beginning of t}le hardening time of which can be adjusted so as to conform with
the requirements of the plant in question. Aluminum compounds such as aluminum
chloride, aluminum sulpha~e and aluminum hydroxide are examples of hardening
accelerators~ while sulplla-tes and sugar derlvatives are suitable as hardening
retardants O
If necessary7 familiar li~uefiers can be added to the base mixture
to provide an additional degree of liqueica-tionO
Additives of other kinds, particularly fibres, are also possible.
Tlle base mixture can be dosed into the mold by either volume or
by waight, in which regard, howeverJ it is the former that is preferred for,
in this case bricks, for the most part constant weight will resultO Possible
variat;ons in the unprocessed density of the base mixture will be evened out
insof~r as the volumetrically dosed quantities are weighed and the density of
the base mixture for the subsequent charge will be adjusted according to the
values so obtainedO This takes place by the appropriate measurement of the
water and/or foam quantities in the base mixture, in which regard it is
specially the quantity of foam that will be adjusted accordingly.
In order to mold in cavities, molds can be used that have suitably
formed plugs; ho~ever, it is preferred to form these cavities by introducing
the plugs into the partially filled mold~ especially from above, through the
cover plate, the mold then being filled with the base mixtureO A totally
enclosed mold and the expansion of the foam simultaneously ensure sharp edges
to the blank that has been molded, ~hereas the pourable consis~ency of the base
mixture permits this ~o rise between the plugs and also permits the formation
of the cavities at very slight mechanical loading of the plugs that are to be
inserted~ The cavities are preferably configured as blind holes.
The foam is either added as such to the base mixture or else is
formed in this by the addition of a foaming agent prior to introduction of the
hase mixture into the molds; however, it is the former method which is preferred.
~oam densitles of c-pproximately ~0 - 100 g/L,, particularly approxi.mately 60 -
~0 g/L are pre:EerredO The foam can also be filled wi~h C02 instead of w:ith
air, which means that as the foam deca~s u-nder the effects of heat C02 ls
liberatedl this leading to additlonal strengthening reactions as in the case of
air mortar~
Since foams are al~ays sensitive to temperature, it is expedient
that the temperature of the base mixture be kept as low as poss:ible until it
is introduced into the mold so that the clurabi:Lity of the foam is for all
practical purposes not reduced by the temperatureO Thus, syntheti.c foams only
possess sufficient durability below 30C, whereas protein foa-.ns can display
adequate durability between the range of 30 - ~0C. According to the foam that
is used and the temperature of the materials that are used as well as the
installation that i.s used, it is possible to keep the temperature of the mixture
of material tha~ contains silicates, cement and water and thus the addition
of an accelerator agent, as ~ell as foam~ constant or dose them according to
th.e starting temperature of the mixturea
At the same ti:me, the cement is to be so adjusted ~ith regard to
the start-up of the hardening reactions b~ the addition of the accelerator
agent that these reactions are initiated first by ~he effects of heat in the
mold, after the expansion of the foam, i.eO, after the prescrib0d end
temperature has been reached, to an appropriate degreeO The quantity of
~ater added to the base mixture also serves to adjust the time ~hen this takes
placeO
In order to simplif~ removal of the blank from the mold and to avoid
a.dhesion to the mold, it is preferred that the mold and if necessary ~he plugs
are ~etted ~ith an appropriate release agent before the base mixture is placed
in the moldO This can be done either by sprayi.ng or by immersion, in which
regard, in the event of the latter, it is expedie-nt to use a sonic cleani-~g
tank f.illed with the release agent in order to remove all of the base mixture
from the mold and from the plugs.
The regular heating of the base mixture by means of an electrical
field is suitable for use on both solid and :Eor ai.r bricks and can also be
assis~ed by heatillg the mold i~sel:E ~contac-t heating~O If the base mixture
in the mold is to be heated by means of a high frequency field, frequenc.ies oE
grea~er than 600 kHz, preferably 10 M~IZ, at voltages of greater than 5 kV can
be used, in which connection :Erequencies of up to 30 M~IZ can be used whereas
generated power output ~lOkW, preferably 60 - 120 kW OI more are used.
In order to produce the blan~s a system is suitable having a.t least
one mold as ~ell as a filllng system and devices to remove the blanks from the
mold and move these onto a transportation deviceO If necessary, plugs are
provided in the mold in order to form the cavities that are separated by ribs
~or ~alls) in the blanks located în the moldsJ The system is provided with a
heating sy~tem of ~hich two elements, which could be the base and the cover
plates for the mold, constitute condenser plates, or else these can be formed
br alternating polarity from the plugs and two outer walls of the mold to which
the high frequency voltage is applied. The base plate for the molds can also
be formed from a circulating conveyor belt that, if necessary, passes through a
post~heating system ~hich could be a heating tunnel~
As a rule a mold remo~al hardness of at least 0~1 N/mm2 is
necessary for the blanks that are going to be removed from the mold but this,
ho~ever, depends on the manner in ~hich the blank is to be handled subsequently.
rf necessary, a blank that has been formed can be subsequently heated, for
example, by lnfrarcd racliation or by hot air during transportation in order
that in this ~a~ -~he stacking hardness that is required for subsequent
storage can be achieved in a short time. In an~ case, the blank hardens after
removal from the mold as a result of the heat ~hat it has absorbed whereas,
ho~ever, as a result of the slight cooling the pressure that is exerted by the
expanded air of the foam on the structure of the blank disappears and the risk
of cracks forming is eliminatedO
Example 1
~ base mixture consisting of the follo~ing is produced:
118 kg of ~uartz powder ~ith a surface area o 1~00 cm2/g (Blaine~
390 kg of rapid cement (Heidelberger Schnellæement)
25~ kg ~ater
358 kg foam ~unprocessed densit~ 60 kg/m3~ foaming agent
alkylarylsulfonate~
The components are placed in a mixer and mixed together for a
period of t~o minutes. The basic mixture so formed is at a temperature of
20Co
The base mixture is poured into a mold of 20 cm x 20 cm x 50 cm and
Brought to a temperatura of 50C homogeneousl~ by heating in a high frequency
field for approximately 35 seconds and then main~ained at this temperature for
a further 25 seconds. The fre~uenc~ of approximately 27 MIIZ at a voltage of
approximately 10 k~ ~ith a generator po~er output of 60 - 90 kW was used. The
~lank that is so produced is then removed from the mold and has a blank
hardness of greater than 0~1 N/mm2.
The blank is then hardened in an autoclave for eight hours at 12 bar
in superheated steam and the ~rick so produced then has a hardness of
approxln)ately 2D 5 n/mm2 and a density of 600 g/m3.
Exann ~e 2
A base mixture is made up of the following:
528 kg of quartz sa.nd (grain size between 0 - 4 mm)
390 kg of Portland cement PZ 55
3O9 kg of aluminwn hydroxide
230 kg of water
2507 kg of foam concentrate ~ratio 1:40 of alkylarylsulfonate to
~ater~
These components are then placed in a mixer and mixed together
for flve minutes and the foaming concentrate initiatedO The temperature of the
base mixture amounts to 20C.
As in Example 1 the base mixture is poured into a mold of 20 cm x
20 cm x 50 cm and brought to a temperature of 50C homogeneously by heating in
a high frequency fieldO However, the heating time in this case is 45 seconds
and the temperature oi 50C is maintained for a further 25 seconds.
The blank is then hardened in steam for twelve hours and a brick
so produced then has a rigidity of approximately 205 N/mm2 and a density of
100 kg/m3.
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