CA1182622A - Process for the production of foam concrete blanks - Google Patents
Process for the production of foam concrete blanksInfo
- Publication number
- CA1182622A CA1182622A CA000401274A CA401274A CA1182622A CA 1182622 A CA1182622 A CA 1182622A CA 000401274 A CA000401274 A CA 000401274A CA 401274 A CA401274 A CA 401274A CA 1182622 A CA1182622 A CA 1182622A
- Authority
- CA
- Canada
- Prior art keywords
- mold
- base mixture
- foam
- process according
- cement
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B28—WORKING CEMENT, CLAY, OR STONE
- B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
- B28B1/00—Producing shaped prefabricated articles from the material
- B28B1/50—Producing shaped prefabricated articles from the material specially adapted for producing articles of expanded material, e.g. cellular concrete
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B28—WORKING CEMENT, CLAY, OR STONE
- B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
- B28B7/00—Moulds; Cores; Mandrels
- B28B7/40—Moulds; Cores; Mandrels characterised by means for modifying the properties of the moulding material
- B28B7/42—Moulds; Cores; Mandrels characterised by means for modifying the properties of the moulding material for heating or cooling, e.g. steam jackets, by means of treating agents acting directly on the moulding material
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B38/00—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof
- C04B38/10—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof by using foaming agents or by using mechanical means, e.g. adding preformed foam
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
- C04B40/02—Selection of the hardening environment
- C04B40/0263—Hardening promoted by a rise in temperature
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Ceramic Engineering (AREA)
- Structural Engineering (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Organic Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Toxicology (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
- Porous Artificial Stone Or Porous Ceramic Products (AREA)
- Producing Shaped Articles From Materials (AREA)
- Moulds, Cores, Or Mandrels (AREA)
Abstract
A B S T R A C T
This 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, particularly material which contains silicate; water;
cement; and foam is produced and placed in a mold, after which the blank, when it displays adequate hardness, is removed from the mold and hardened. In order to be able to produce bricks of a regular density simply and rapidly, a temperature dependent accelerating additive for hardening the base mixture is added to the base mixture before it is placed in the mold, the base mixture that is in the mold being heated by means of an electrical high frequency field homogeneously to a temperature of approximately 40 - 80°C, and the heating of the base mixture in the mold being carried out so quickly that the expansion caused by the heating of the base mixture is terminated before the cement begins to harden. The blank is removed from the mold after a heating period of 20 - 120 seconds.
This 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, particularly material which contains silicate; water;
cement; and foam is produced and placed in a mold, after which the blank, when it displays adequate hardness, is removed from the mold and hardened. In order to be able to produce bricks of a regular density simply and rapidly, a temperature dependent accelerating additive for hardening the base mixture is added to the base mixture before it is placed in the mold, the base mixture that is in the mold being heated by means of an electrical high frequency field homogeneously to a temperature of approximately 40 - 80°C, and the heating of the base mixture in the mold being carried out so quickly that the expansion caused by the heating of the base mixture is terminated before the cement begins to harden. The blank is removed from the mold after a heating period of 20 - 120 seconds.
Description
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 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
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 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
2~
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, 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.
-lQ~
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, 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.
-lQ~
Claims (11)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for the production of foam concrete blanks in which a pourable base mixture consisting in the main of granular material, especially that which contains silicates; water; cement; and foam wherein the foam as such is added to the base mixture or else produced in the base mixture by means of a foaming agent, is produced and placed in a mold, after which the blank, when it displays sufficient hardness, is removed from the mold, characterized in that:
a. a temperature dependent accelerating additive for hardening the base mixture is added to the base mixture before it is placed in the mold;
b. the base mixture in the mold is heated homogeneously by means of an electrical high frequency field to a temperature of approximately 40 -80°C;
c. the heating of the base mixture contained in the mold is under-taken so quickly that the expansion caused by the heating of the base mixture is substantially terminated before cement hardening begins;
d. after heating for 20 - 120 seconds the blank is removed from the mold.
a. a temperature dependent accelerating additive for hardening the base mixture is added to the base mixture before it is placed in the mold;
b. the base mixture in the mold is heated homogeneously by means of an electrical high frequency field to a temperature of approximately 40 -80°C;
c. the heating of the base mixture contained in the mold is under-taken so quickly that the expansion caused by the heating of the base mixture is substantially terminated before cement hardening begins;
d. after heating for 20 - 120 seconds the blank is removed from the mold.
2. A process according to Claim 1, in which a mold that can be closed with reference to the egress of the base mixture is used, this being filled with the base mixture to the point that the remaining volume corresponds to the expansion of the base mixture produced by the heating.
3. A process according to Claim 1 or 2, in which an accelerator for the cement is used as an accelerating additive this being activated by increased temperature.
4. A process according to Claim 1 or 2, in which an accelerator in combination with a retardant for the cement is used as the accelerating additive, this being adjusted so that the activation of the cement takes place more or less at the heating temperature foreseen for the base mixture in the mold.
5. A process according to Claim 1 or 2, in which a fast setting cement is used as the accelerating additive and at least a part of the cement.
6. A process according to Claim 1 or 2, in which the base mixture is meted volumetrically into the mold, the quantity so meted is proofed by weight, the density of the base mixtures for subsequent charges being adjusted by changing the additives of water and/or foam in accordance with gravimetric measurement.
7. A process according to Claim 1 or 2, in which a base mixture is used that contains a foam with a foam density of approximately 40 - 150 g/L.
8. A process according to Claim 1 or 2, in which the blank that has been removed from the mold is heated during transportation.
9. A process according to Claim 1, in which the temperature range of step (b) is 45 - 60°C.
10. A process according to Claim 1 or 9 in which the time range of step (d) is 25 - 60 seconds.
11. A process according to Claim 1 or 2, in which a base mixture is used that contains a foam with foam density of approximately 60 - 80 g/L.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3115888 | 1981-04-21 | ||
| DEP3115888.9-45 | 1981-04-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1182622A true CA1182622A (en) | 1985-02-19 |
Family
ID=6130536
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000401274A Expired CA1182622A (en) | 1981-04-21 | 1982-04-20 | Process for the production of foam concrete blanks |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0076838B1 (en) |
| JP (1) | JPS58500522A (en) |
| CA (1) | CA1182622A (en) |
| DE (1) | DE3260706D1 (en) |
| DK (1) | DK156132C (en) |
| WO (1) | WO1982003622A1 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3817831A1 (en) * | 1988-05-26 | 1989-11-30 | Sicowa Verfahrenstech | Process for producing blocks |
| US5063967A (en) * | 1989-12-06 | 1991-11-12 | Stephens Patrick J | Pumpable cement grout |
| DE102005018693A1 (en) * | 2005-04-22 | 2006-11-02 | Graf von der Schulenburg-Wolfsburg, Günzel, Dr. | Preformed component of porous concrete has inlay of netting formed from flexible thread, and with brown coal or coal ash or blast furnace sand is added to porous concrete as aggregate |
| EP1925760A3 (en) * | 2006-10-26 | 2015-10-14 | Kanaflex Corporation Inc. | Lightweight Cement Panel |
| EP2197641B1 (en) * | 2007-08-31 | 2011-02-23 | Danish Concrete Technology Holding Aps | Process for curing and drying concrete |
| DE102013217864B4 (en) | 2012-09-07 | 2018-03-08 | Helmholtz-Zentrum Für Umweltforschung Gmbh - Ufz | Method for curing hydraulically setting building material mixtures and treatment device |
| DE102019113570A1 (en) * | 2019-05-21 | 2020-11-26 | WEKO Consulting and Engineering Ltd. | Process for the production of a foam concrete and a building element |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2485742A (en) * | 1948-03-03 | 1949-10-25 | Jr Benjamin M King | Process for molding cellular products |
| DE1207255B (en) * | 1960-02-06 | 1965-12-16 | Coignet Construct Edmond | Process to accelerate the hardening of heavy or cast concrete |
| US3192291A (en) * | 1962-05-15 | 1965-06-29 | Pratt & Whitney Inc | Method of curing cementitious material by radio frequency energy |
| JPS508818A (en) * | 1973-05-28 | 1975-01-29 | ||
| US4036301A (en) * | 1974-10-29 | 1977-07-19 | Standard Oil Company (Indiana) | Process and composition for cementing casing in a well |
| JPS55162468A (en) * | 1979-06-06 | 1980-12-17 | Nippon Concrete Ind Co Ltd | Lightweight foamed concrete |
-
1982
- 1982-04-20 DE DE8282901414T patent/DE3260706D1/en not_active Expired
- 1982-04-20 EP EP82901414A patent/EP0076838B1/en not_active Expired
- 1982-04-20 JP JP57501528A patent/JPS58500522A/en active Granted
- 1982-04-20 WO PCT/EP1982/000084 patent/WO1982003622A1/en active IP Right Grant
- 1982-04-20 CA CA000401274A patent/CA1182622A/en not_active Expired
- 1982-11-30 DK DK532082A patent/DK156132C/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| EP0076838A1 (en) | 1983-04-20 |
| DK156132C (en) | 1989-11-20 |
| DK156132B (en) | 1989-06-26 |
| EP0076838B1 (en) | 1984-09-12 |
| DK532082A (en) | 1982-11-30 |
| WO1982003622A1 (en) | 1982-10-28 |
| JPH033634B2 (en) | 1991-01-21 |
| DE3260706D1 (en) | 1984-10-18 |
| JPS58500522A (en) | 1983-04-07 |
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