GB2124538A

GB2124538A - Moulding concrete panels

Info

Publication number: GB2124538A
Application number: GB08219301A
Authority: GB
Inventors: Takao Kataishi; Iwazou Seo; Masatoshi Kanou
Original assignee: Misawa Homes Co Ltd
Current assignee: Misawa Homes Co Ltd
Priority date: 1982-07-03
Filing date: 1982-07-03
Publication date: 1984-02-22
Also published as: DE3225787A1; GB2124538B; FR2530528A1; FR2530528B1; DE3225787C2

Abstract

A process is described for producing a light-weight cellular concrete panel wherein a cellular concrete slurry is disposed in a mould, released from the mould after the setting thereof, and is subjected to curing. The upper surface of the cellular slurry, while in a plastic state in the mould, is depressed by a roller or plate in order to produce a compressed surface of the concrete panel. This process provides a lightweight cellular concrete panel having a compressed surface which is smooth and possesses mechanical strengh and also is waterproof.

Description

SPECIFICATION Process for forming a surface of a light-weight cellular concrete panel Background of the Invention The present invention relates to a process for forming a surface of a light-weight cellular concrete panel, and more particularly to a process for defining the upper surface of a cellular concrete slurry cast in a mould.

Cellular concrete panels are widely used for external walls of prefabricated buildings. To form a decorative pattern or relief on the outer surface of a cellular concrete panel wall, a cellular slurry composed of cements, concrete admixtures, water, etc. is conventionally cast into a mould having a female pattern formed on the inner bottom surface thereof. After the setting of the cellular slurry, it is released from the mould and then introduced into an autoclave where it is subjected to curing at a high temperature and pressure. Thereafter, the light-weight panel is subjected to finish painting to obtain a finished product.

When a post foam cementitious or cementinuous slurry is used, in the casing operation of the above prior process, a rise portion of the foamed slurry which lies beyond the upper peripheral edges of the mould is removed by a scraper or the like, and thus a considerable amount of valuable slurry is lost, which results in increase in cost of the panel. After the curing, the prior cellular concrete panel has rough surfaces which are not proper for the finish painting.

Further, the prior cellular concrete panel is poor in waterproof and mechanical strength such as surface hardness, abrasion resistance, and the like.

Thus, the surfaces of the panel can easily get scratches and cracks and may be partly break off during the handling thereof.

Summary of the Invention Accordingly, it is an object of the present invention to provide a process for forming a surface of a light-weight cellular concrete panel, the surface being smooth and suitable for a finish coating ground.

It is another object of the present invention to provide a process for forming a surface of a lightweight concrete panel, the surface being excellent in waterproof and mechanical strength and hence less liable to the cracked, scratched or broken off.

It is a further object of the present invention to provide a process for forming a surface of a lightweight concrete panel in which the rise portion of the foamed concrete slurry which is removed according to the prior art can be effectively and economically used.

It is a still further object of the present invention to provide a process for forming a surface of a cellular concrete panel in which the productivity of the panel is improved.

With the above and other objects in view, the present invention provides a process for forming a surface of a light-weight cellular concrete panel wherein a cellular concrete slurry is disposed in a mould, released from the mould after the setting thereof, and is subjected to curing, the improvement which comprises the step of depressing the upper surface of said slurry in a plastic state in the mould for defining a compressed surface of the concrete panel.

The process according to the present invention is useful for building materials, such as external walls of prefabricated buildings.

Brief Description of the Drawings The invention will now be described by way of example with reference to the accompanying drawings in which: FIG. 1 is a perspective view of an apparatus used in the present invention in which a cementinous slurry is poured with a bucket into a mould; FIG. 2 is a perspective view of the mould in Fig.

1 in which a steel assembly is disposed; FIG. 3 illustrates the mould in Fig. 1 within which the slurry is depressed; FIG. 4 illustrates the depressed slurry within the mould in Fig. 1; FIG. 5 illustrates the mould in Fig. 1 within which the slurry is depressed by a pattern roller; FIG. 6 illustrates the cementinous slurry within the mould ;n Fig. 1 over which fine light-weight aggregates and the like are scattered; FIG. 7 illustrates the cementinous slurry over which the fine light-weight aggregates and the like were scattered, the slurry being depressed by a flat roller; FIG. 8 illustrates a temperature v. time curve for autoclave curing of a concrete panel; FIGS. 9 through 11 illustrate specific gravity v.

distance curves of finish cellular concrete panels in cross-section.

Detailed Description of the Invention The cellular concrete slurry may according to the present invention be a pre-foamed cementinous slurry, a post-foamed cementinous slurry or a mixture of both. These slurries can be prepared by any of conventional processes for producing cellular cementinous slurries for lightweight concrete panels.

The pre-foamed cementinous slurry used in the present invention may be prepared by mixing a foam and a cement paste which is previously prepared by mixing a cement material such as portland cements, fly-ash cement, silica cement and the like and water. In order to form the prefoamed slurry, in addition to the above-mentioned ingredients use may be made of a small proportion of additives, which are conventionally used in preparing various kinds of cementinous slurries for light-weight concrete panels e.g., limes, aggregates, silica powder, quick hardening materials, setting retarders, cement admixtures, etc. The limes include quick lime and slaked lime.

The aggregates include fo,ç,example light-weight aggregates such as sand, gravel and the like. As the quick hardening material, that containing alumina such as alumina cement may be used.

The setting retarders may include inorganic retarders such as gypsums and organic retarders such as hydroxycarboxylic acid and its salt, sucrose, etc. The cement admixtures include for example dispersing agents, AE agent, etc.

The foam utilized in the above pre-foamed cementinous slurry may be prepared by mixing water and a foaming agent such as surfactants and protein foaming agent. The surfactant includes for example alkylbenzene sulfonates. The protein foaming agent includes for example decomposed keratin protein.

The post-foam cementinous slurry according to the present invention may be prepared by previously mixing a foaming agent with the above mentioned cementinous slurry. The foaming agent may include aluminum powder, hydrogen peroxide, etc. After being cast in a mould, the post-foam cementinous slurry is allowed to foam.

Furthermore, according to the present invention, the above-described pre-foaming agent may be previously mixed with the cementinous slurry, which is then stirred to form a pre-foamed cementinous slurry which is thereafter poured into a mould.

Alternatively, the cellular slurry used in the present invention may be prepared by combining at least two of the above three procedures for preparing pre- or post-foam cellular slurry.

The cementitious slurry thus prepared is, as shown in Fig. 1, cast with a bucket 3 into a mould 1 which may be of any conventional shape, in this embodiment a rectangular shape shown therein.

For producing a reinforced concrete panel, a steel assembly 2 which is previously subjected to conventional rustproofing including degreasing, water washing, and mortar paste dip treatments is disposed within mould 1 as shown in Fig. 2 before the casting of the cellular slurry in that mould. The upper surface of the cast slurry is leveled by a suitable means such as plate, and may be positioned somewhat above the upper edges of mould 1. After the casing of the cementinous slurry, it is according to the present invention allowed to be set to a plastic state with a proctor value of not larger than about 100 psig and preferably about 2 to 10 psig in which when mould 1 is inclined, the slurry will not flow out of the mould. The time required for obtaining such slurry in the plastic state depends on its property.

Beyond the upper limit, i.e., about 100 psig, the slurry in the plastic state is liable to be damaged or fractured when subjected to the subsequent depression treatment which will be described hereinafter. For the post-foamed slurry, after being hardened to the plastic state, a rise portion thereof may be leveled or partly removed by means of a scraper so that the upper surface of the slurry is positioned above the upper edges of mould 1 at a height substantially corresponding to a compression allowance as will be described later.

Before subsequent depression of the upper surface of the cellular slurry, it may be subjected to conventional moisture curing.

When the cellular slurry is hardened to the above plastic state, it is subjected to the depression treatment in which the upper surface thereof is depressed by a suitable depression device for defining a flat compressed surface of a concrete panel which is to be produced. The depression device may be a flattening roller 4 as shown in Fig. 3, pressing plate (not shown) or the like. The roller 4 may be made of plastic material, stainless steel, brass, etc. To the opposite ends of the roller 4 there is each fixedly attached a pinion 5 which meshes with a rack 6 fixedly attached to the upper edge of each side wall 7 of mould 1. A shaft 8 is secured at one end to the center of each pinion 5 to project axially therefrom. The free end of each shaft 8 has a handle 9 secured thereto for rotation about the shaft.In the depressing operation, roller 4 is lifted up and placed on the cellular slurry within mould 1 adjacent a front wall 10 of that mould and then two operators push handles 9 backwards to roll roller 4 along mould 1 with racks 6 and pinions 5 engaged with each other and thereby the slurry 1 6 is compressed and the upper surface thereof is depressed to a predetermined height and becomes flat and compact as shown in Fig. 4. In this depressing treatment, the compression allowance of the concrete slurry with mould 1 is generally within about 10 mm and is preferably about 2 to 7 mm for the concrete slurry of thickness about 50 to 250 mm. Beyond the upper limit, the cellular slurry in the plastic state is liable to be damaged or fractured.The compression allowance may be set by adjusting the level of the upper surface of the cellular slurry with respect to the contact surface of roller 4.

Thereafter, the depressed cellular slurry is allowed to be solidified and then released from mould 1 by a conventional releasing means (not shown) to obtain a cellular concrete panel. The concrete panel is subjected to a conventional curing treatment including moisture curing and/or autoclave curing before or after the release frorn the mould. The conditions of this curing treatment depends on the nature of the cellular concrete slurry.

Then, the concrete panel is dried for about a few weeks and subsequently may be subjected to coating treatment if needed. The cellular concrete panel thus produced is transported for a destination or stored for later use.

In place of the flattening roller 4 used in the depression treatment, patterning device such as a roller 11 shown in Fig. 5 or plate having a pattern 12 formed on the contact surface thereof may be used for forming a decorative embossed pattern 13 or relief on a surface of a cellular concrete panel.

Before the depression operation with the rollers and the like, a powder or particulate of fine light weight aggregates, fibers such as cellulose, nylon, acrylic, carbon fibers and asbestos, or pigments such as titanium oxide may be scattered over the upper surface of the cellular slurry in a fluid or plastic state, which is disposed within the mould, for even distribution to improve its mechanical strength and the like, and then the slurry is depressed by a suitable depressing means such as roller 4 for positively adhering the scattered material to it.As shown in Fig. 6, such material 14 which is scattered may be supplied from the bottom of a conventional bucket 1 5 secured to a frame (not shown) over the upper surface of a cellular concrete slurry 16 within a mould 17 which is passing below bucket 15, the mould 1 7 being provided with two pairs of rollers 1 8 (only two of which are shown) rotatably secured to the lower portions thereof for movement. Then, the scattered material is positively adhered to the upper surface of the cellular slurry as shown in Fig.

7 by the depression of the depression device such as roller 4.

Furthermore, after the positive adhesion of such scattered material to the upper surface of the cellular slurry, that surface may be subjected to a second depression by the above-mentioned depression device for compression or by the patterning device for the formation of a pattern thereon in the same manner as in Fig. 5.

EXAMPLE 1 Portland cement, silica powder, and water were prepared each in an amount of 50 kg and mixed by a mortar mixer at 100 rpm for 5 minutes to form a slurry A. On the other hand, 0.5 kg of a foaming agent of decomposed keratin protein and 10 kg of water were mixed by a high shearing forced mixer at 3000 rpm to obtain a form having a specific gravity of 0.046. The foam in an amount of 200 1 and the slurry A in an amount of 85 1 were mixed in a mortar mixer for 5 minutes to form 300 1 of a cellular slurry having a specific gravity of 0.53, which was poured at once into a mould 100 cm wide, 300 cm long, and 9 cm deep of the type as shown in Fig. 1 and having a rustproofed steel assembly disposed therein so that the upper surface of the cellular slurry became leveled.The steel assembly was of the type as shown in Fig. 1 and consisted of steel rods of 5 mm diameter, of 100 mm x 100 mm pitch, and welded together in a grille. Then, the slurry was subjected to moisture curing at 500C for 5 hours. When the proctor value of the cellular slurry thus cured reached to 5 psig, the upper surface thereof was depressed with a compression allowance of 5 mm by means of a roller of the type as shown in Fig. 3, the roller having a stone bond pattern formed on the surface thereof. Thereafter, the slurry within the mould was subjected to a second moisture curing at 500C for 5 hours and then released from the mould. Then, the cellular concrete panel thus set was introduced into an autoclave for a third curing at a vapor pressure of 10 kg/cm2, of which temperature v. time curve is shown in Fig. 8.

Finally, the panel was allowed to stand at room temperature for two weeks for drying. The specific gravity of the thus produced cellular concrete panel in a cross-section direction from one surface as pressed by the roller to the opposite surface thereof was determined and the results are plotted in Fig. 9, from which it is clear that an inclined compact layer B was formed continuously with the one surface. The finish product had a stone bond pattern formed on the one surface which was smooth and suitable for finish coating ground and furthermore excellent in waterproof and mechanical strength such as crack resistance, etc.

EXAMPLE 2 Sodium citrate in an amount of 2 kg was dissolved in 250 kg of water. Then, the aqueous solution thus prepared, 250 kg of portland cement, 250 kg of silica sand, and 50 kg of alumina cement were mixed by a mortar mixer under the same conditions as Example 1 to form a slurry C. To form a foam, 25 kg of water and 2.5 kg of decomposed keratin protein as a foaming agent were mixed as in Example 1. The foam and slurry C thus obtained were mixed by another mortar mixer for 5 minutes to form a cellular slurry having a density of 0.805, which was then cast into a mould 200 cm wide, 500 cm long, and 95 cm deep of the type as shown in Fig.

1 at once so that the upper surface of the concrete slurry was leveled and positioned at a height of 7.5 mm above the upper edge of the mould. After the cellular concrete slurry within the mould was allowed to stand at 300C for 20 minutes, a silica powder having a grain size from 0.2 to 0.5 mm was scattered over the concrete slurry at a rate of 1 50 g/m2 as shown in Fig. 6, which was then allowed to stand at 30CC for 5 minutes. When the proctor value of the cellular concrete slurry reached to 3 psig, it was depressed by a flat roller of the type as shown in Fig. 3 with a compression allowance of 2.5 mm and then further by a pattern roller as in Example 1 with a compression allowance of 5 mm.After 20 minutes from these depression treatments, the solidified cellular concrete panel was released from the mould and then subjected to moisture curing at 300C for 8 hours. The concrete panel thus moisture cured was subjected to autoclave curing as in Example 1. The specific gravity of the cellular concrete panel thus produced in a cross-section direction from one surface as depressed by the rollers to the opposite surface thereof was determined and the results are plotted in Fig. 10. The panel thus obtained had an outer wall surface excellent in smoothness, waterproof, and mechanical strength.

EXAMPLE 3 The procedure of Example 2 to prepare the cellular concrete slurry was substantially repeated except that 500 kg of portland cement was used and no silica sand was used. The slurry thus obtained was allowed to stand at 300C for 30 minutes. Then, glass fiber of 1 cm length and about 0.1 to 0.2 mm diameter was scattered over the upper surface of the slurry within the mould, which surface was then depressed by a wooden depression plate of a rectangular shape. After 10 minutes from this depression, the upper surface of the slurry was again pressed down by another wooden depression plate of a rectangular shape having a stone bond pattern attached to the depression surface thereof, and it was then subjected to moisture curing at 500C for 10 hours.

Thereafter, the concrete panel thus cured was released from the mould and allowed to stand at room temperature for 2 weeks. The product thus obtained had an outer wall surface excellent in smoothness, waterproof, and mechanical strength.

EXAMPLE 4 The following components were mixed each in the specific amount by a mortar mixer for 10 minutes to form a concrete slurry having a specific gravity of 0.6: Portland cement 40 kg Silica powder 60 kg Water 50 kg Aluminum powder 230 g The concrete slurry thus prepared was cast into a mould, of the type as shown in Fig. 1,200 cm wide, 100 cm long, 10 cm deep at once for foaming, and was subjected to curing at 300C for 4 hours. Then, a rise portion of the foamed concrete slurry was partly removed by a scraper so that the upper surface of the slurry was leveled and positioned at a height of 5 mm above the upper edges of the mould.After sand having a grain size of 0.5 to 2 mm and a specific gravity of 0.3 was scattered over the upper surface of the foamed concrete slurry, which was then depressed by a flat roller of the type as shown in Fig. 3 with a compression allowance of 5 mm when the proctor value thereof reached to 10 psig.

The thus compressed cellular concrete slurry within the mould was introduced into an autoclave for curing under the same conditions as in Example 1, and then released from the mould. The cellular concrete panel thus obtained has an outer wall surface excellent in smoothness, in waterproof and mechanical strength. The specific gravity of the cellular concrete panel in a crosssection direction from one surface depressed by the roller to the opposite surface was determined and the results are plotted in Fig. 11.

COMPARATIVE TEST 1 Example 1 was repeated except that in this test no depression treatment was applied to the cellular slurry. The specific gravity of the finish product in a cross-section direction from one surface to the opposite surface thereof was substantially uniform and about 0.5. The upper surface of the finish panel which corresponds to the surface depressed in Example 1 was rough and not suitable for finish coating ground, and furthermore poor in waterproof and mechanical strength.

Claims

1. In a process for producing a light-weight cellular concrete panel wherein a cellular concrete slurry is disposed in a mould, released from the mould after setting thereof, and is subjected to curing, the improvement which comprises the step of: depressing the upper surface of said slurry in a plastic state in the mould for defining a compressed surface of the concrete panel.

2. The process as recited in claim 1, wherein said depressing step comprises the step of patterning said upper surface of the cellular slurry in a plastic state for forming a pattern thereon.

3. The process as recited in claim 1 or 2, before said depressing step further comprising the step of scattering a material for improving the property of the upper surface of the panel over the upper surface of said cellular slurry, whereby said scattered material is positively adhered to the slurry by the subsequent depressing step.

4. The process as recited in claim 3, wherein said material is a light-weight aggregate, fiber, and/or pigment.

5. The process as recited in claim 3, after said depressing step, further comprising the step of second depressing said material adhered surface of the slurry in the plastic state for defining a compressed surface of the concrete panel.

6. The process as recited in claim 5, wherein said second depressing step comprises the step of patterning said material adhered surface of the slurry in the plastic state for forming a pattern thereon.

7. The process as recited in claim 1 or 2, wherein said depressing step is performed when the proctor value of said slurry is not larger than about 100 psig.

8. The process as recited in claim 1 or 2, wherein said proctor value is within a range of about 2 to about 10 psig.