GB2046339A

GB2046339A - Method of constructing aerated concrete wall elements

Info

Publication number: GB2046339A
Application number: GB7911571A
Authority: GB
Original assignee: AEROCON INTERNATIONAL HOUSING
Current assignee: AEROCON INTERNATIONAL HOUSING
Priority date: 1979-04-03
Filing date: 1979-04-03
Publication date: 1980-11-12
Also published as: GB2046339B; BE882538A; OA06503A

Abstract

A method of constructing an aerated concrete wall or other non- horizontal panel comprises erecting formwork (2,3) to define one side only of the wall or panel, preferably positioning reinforcement (4) adjacent the formwork and then spraying aerated concrete against the formwork to form the wall or panel with any reinforcement embedded therein. The concrete is left to set and the formwork removed when the concrete is sufficiently hardened to be self supporting. Preferably the aerated concrete which is sprayed incorporates a plasticer and is sprayed in a succession of passes over the formwork. The first and/or final passes may be of non-aerated concrete. <IMAGE>

Description

SPECIFICATION Method of constructing aerated concrete wall elements The present invention relates to the construction of walls and upright or inclined panels or buildings from aerated concrete, also known as gas-formed concrete.

The method of this invention can be used for building walls and vertical or inclined panels of all structures including but not limited to one-storey and multi-storey houses and factories. It can be used in the construction of load-bearing walls, partition walls, panel walls and the vertical elements of all types of structures, as well as inclined panels, e.g.

for pitched roofs.

Hitherto aerated concrete has been used in the construction of walls and vertical panes but the method of construction used involved either erecting formworkto surround completely the wall to be cast and pouring the aerated concrete into the space surrounded by form-work or alternatively precasting the wall or panel and later lifting the pre-cast wall or panel into place. Difficulties with casting on site have led pre-casting in a factory to be the favoured method of fabricating aerated concrete, even though this entails transporting the pre-cast components to the site.

It has also been known to make walls by spraying concrete, but only ordinary, i.e. non-aerated concrete has been used in such spraying. Spraying is a technique which has been avoided for aerated concrete because aerated concrete is generally more fluid than non-aerated concrete.

We have now found that spraying can be successfully and advantageously employed in making concrete walls and upright panels. According to the present invention there is provided a method of constructing an aerated concrete wall or other upright or inclined panel which comprises erecting formwork to define one only of the opposite upright surfaces of the wall or panel, spraying aerated concrete against the formwork (optionally preceded and/or followed by a layer of non-aerated concrete) to form a wall or panel thereagainst, allowing the concrete to set, and removing to be self supporting.

By means of this method a wall can be formed, in its required position, using formwork on only one side of the wall. Because one surface of the wall is exposed before the concrete has hardened, this surface can be given a suitable finish, such as by trowelling, before the concrete hardens, with the result that a smooth finished surface is obtained.

Alternatively, the concrete can be left as sprayed, giving a tyrolean-type finish. The opposite surface may require some finishing after removal of the formwork, this will depend on whether the quality of the formwork was such as to give an acceptable finish.

The concrete can be aerated in various ways, and the aerating gas may be other than air: the term "aerated concrete" covers concrete aerated with other gases. Indeed the preferred method for aerating the concrete is to mix finely divided aluminium powder into the concrete just prior to spraying. The aluminium reacts chemically with the alkaline concrete mixture liberating hydrogen gas which aerates the concrete.

Another known method by which concrete can be aerated is to mix into it a pre-formed foam, made by beating air into a liquid which forms a stable foam.

The aerated concrete can be sprayed with conventional concrete spraying equipment.

It is preferred that a plasticizer is incorporated into the concrete mix. This enhances its workability and enables the water content to be reduced. It is also preferred, when foaming is effected with aluminium powder, to incorporate a wetting agent to promote uniform dispersion of the aluminium powder. The extent of aeration of the concrete can be varied as desired, and suitable amounts of aluminium powder, plasticizer and wetting agent can be determined by experiment.

Generally, reinforcing rods or mesh will be incorporated in the wall. The reinforcement can be positioned adjacent the formwork, in conventional manner, and the concrete sprayed through it until it becomes embedded.

It is conceivable that a full wall thickness could be sprayed in a single pass over the formwork, for example if several layers of reinforcing mesh were provided. However, in general, it is desirable to spray the concrete onto the formwork in a number of passes in each of which the amount sprayed is sufficiently small that it does not slough off from the formwork or the previously sprayed material. A sufficient interval should be allowed to elapse between successive passes to allow the already sprayed concrete to begin its set, and prevent sloughing of as the thickness is increased. Frequently a thickness of 1 inch (2.5 cm) or more can be sprayed in a single pass, and a sufficient interval of 10 minutes or so will be provided simply by the time taken to complete a single pass over the wall area being sprayed. The incorporation of plasticizer assists in preventing sloughing off.

It is possible for the concrete sprayed in a final pass not to be aerated - this will give a harder skin to the wall, at the exposed surface, and this nonaerated layer can be given a suitable finish before it hardens. Likewise, the concrete sprayed in a first pass over the formwork might not be aerated, giving a harder skin at that side of the wall.

The method of this invention can be employed equally well both for single walls and intersecting walls. The method will be further explained with reference to the accompanying drawings, which are given by way of example only, and wherein Figure 1 is a perspective view, partially sectioned, of formwork prepared for the spraying of a wall; Figure 2 is a similar view after spraying is complete; Figure 3 is a perspective view of the formwork for two walls meeting at a corner; and Figures 4 and 5 are plan views showing intersecting walls.

Referring first to Figure 1, a conventional concrete floor slab and foundation for a building is indicated by numeral 1. Standing on this, formwork panels 2 are erected to line and level on one side only of the intended wall and then fixed in their desired position such as with props 3. Suitable steel reinforcing mesh 4 is riext placed in position and secured in conventional manner. Aerated concrete incorporating plasticizer and wetting agent is sprayed under pressure against the formwork, spreading an even coating over the wall area. The process is repeated by further passes over the area, at intervals of 10 minutes or so until the desired wall thickness 5 is obtained, with the reinforcement embedded in the wall 6 formed.

The exposed surface 7 is trowelled smooth or patterned according to the finish desired. When the concrete has hardened enough to be self-supporting the formwork 2 is removed.

Where a single wall isto be constructed, an upright stop board is placed at the end of the formwork to define the upright end of the wall.

If two walls meet at a corner, formwork panels 2 are erected as before on one side only of each intended wall, conveniently on the inside of the corner as shown in Figure 3 and either one wall is completed before the other is sprayed or both walls sprayed together. The layer of steel reinforcement in one wall stops at the corner and the reinforcement in the other wall bends round the corner as shown at 8 and overlaps the reinforcement of the other wall.

Figure 4 shows the case where a wall 10 meets an adjacent wall 1 art a Tjunction. The principle of erecting formwork 2 on one side only of each intended wall still applies, being carried out as shown in Figure 4. The desired thickness is sprayed in a succession of passes as before. The reinforcing mesh 12 in the discontinued wall 10 bends at the intersection and its portion 13 overlaps the reinforcing mesh 14 of the adjacent continuous wall 11.

Figure 5 shows two continuous walls crossing.

Formwork 2 is erected on one side only of each intended wall, and the reinforcing mesh 15 of one wall stops at the junction, being provided with bent over portions 16 overlapping the mesh 17 of the other wall.

Claims

1. A method of constructing an aerated concrete wall or other upright or inclined panel which comprises erecting formwork to define one only of the opposite upright surfaces of the wall or panel, spraying aerated concrete against the formwork (optionally preceded and/orfollowed by a layer of non-aerated concrete) to form a wall or panel thereagainst, allowing the concrete to set, and removing the formwork after the concrete has hardened sufficiently to be self supporting.

2. A method according to claim 1 wherein steel reinforcing rods or mesh are positioned adjacent the formwork before spraying, and become embedded in the wall or panel which is formed.

3. A method according to claim 1 or claim 2 wherein non-aerated concrete is first sprayed against the formwork, and/or non-aerated concrete is finally sprayed to form the exposed surface.

4. A method of constructing an aerated concrete wall or other upright or inclined panel which comprises erecting formwork to define one only of the opposite upright surfaces of the wall or panel, positioning reinforcement adjacent the formwork, and spraying concrete against the formwork in a succession of passes over the formwork, aerated concrete being sprayed in all the passes, or all except the first and/or final passes, the amount of concrete sprayed in each pass being sufficiently small and the interval between passes being sufficiently long that the material does not slough off the formwork whereby a wall is formed against the form-work with the reinforcement embedded in the wall, allowing the concrete to set, and removing the formwork after the concrete has at least hardened sufficiently to be self supporting.

5. A method according to any one of the preceding claims wherein a finishing surface is applied by hand to the exposed surface of the aerated concrete after spraying and before setting of the concrete sprayed in the final pass.

6. A method according to any one of the preceding claims wherein the aerated concrete incorporates a plasticizer.

7. A method according to any one of the preceding claims wherein the aerated concrete incorporates a wetting agent.

8. A method according to any one of the preceding claims wherein the concrete is aerated by mixing aluminium powder into it prior to spraying.

9. A method according to any one of the preceding claims wherein only aerated concrete is sprayed.

10. A method according to any one of the preceding claims wherein the wall or other panel is vertical.

11. A method of constructing an aerated concrete wall substantially as herein described with reference to any of the accompanying drawings.