Controlling Cracks in Cementitious Materials

Description

FIELD OF INVENTION

This invention relates to means for controlling cracks in cementitious materials, for example in concrete.

BACKGROUND

In the context of concrete construction it is common for a body of concrete to crack as it sets. While such cracking is normally inevitable when working with a large volume of concrete it is desirable, from a structural point of view, to control the location of the cracks. It is accordingly an object of at least one embodiment of the present invention to go at least some way towards controlling cracks in concrete, or to at least provide the public with a useful choice.

It should be appreciated that terms pertaining to orientation, for example “upwards” etc, if and when used herein, should be taken as referring to the item concerned when in a normal in-use orientation unless otherwise conveyed.

It should also be appreciated that the term “comprising”, and derivatives thereof such as “comprises” etc, should be interpreted to mean “consisting or including”—ie they are not intended to be limiting.

SUMMARY OF THE INVENTION

According to one aspect of the invention there is provided means for controlling cracking in a body of cementitious substance, the means for controlling cracking having an elongate base, elongate side wall portions extending from the base and angling towards one another, and an aperture or apertures in the side wall portions, the means for controlling cracking formed such that when it is in use it can be positioned base down such that a cementitious substance prone to cracking can be poured around it and at least partially through it such that cracks which subsequently form within the cementitious substance will occur at or in the vicinity of the means for controlling cracking.

Preferably the cementitious substance comprises concrete.

Preferably the side wall portions, together with a portion of the base between them, form a triangular shape when viewed in transverse cross section.

Preferably there is an extension extending upwards from an apex of the triangular shape.

Preferably the means for controlling cracking in a body of cementitious substance is in combination with a joint for combining a number of said means for controlling cracking.

According to a further aspect of the invention there is provided means for controlling cracking in a body of cementitious substance, the means having an elongate base, an elongate wall portion extending upwards from the base such that the base and the wall portion are substantially in an inverted “T” shape, and an aperture or apertures in the wall portion, the means for controlling cracking formed such that when it is in use it can be positioned base down such that a cementitious substance prone to cracking can be poured around it and at least partially through it such that cracks which subsequently form within the cementitious substance will occur at or in the vicinity of the means for controlling cracking.

Preferably the cementitious substance comprises concrete.

Preferably the aperture or apertures make up approximately 50% or more of the wall or wall portions, as the case may be.

According to a further aspect of the invention there is provided means for controlling cracking in a body of cementitious substance, the means having two elongate substantially V shaped portions, an elongate wall portion extending out from the interior of the apex of one of the V shaped portions and extending to the apex of the other V shaped portion, and an aperture or apertures in the wall portion, the means for controlling cracking formed such that when it is in use it can be positioned such that a cementitious substance prone to cracking can be poured around it and at least partially through the aperture or apertures such that cracks which subsequently form within the cementitious substance will occur at or in the vicinity of the means for controlling cracking.

Preferably the two V shaped portions have their apexes oriented in substantially the same direction.

Optionally the apexes of the V shaped portions are oriented in substantially opposite directions.

Optionally one of the V shaped portions is substantially larger than the other V shaped portion.

Preferably the aperture or apertures make up at least substantially 50% of the surface area of the wall portion.

According to a further aspect of the invention there is provided means for controlling cracking in a body of cementitious substance, the means having an elongate base portion and an elongate wall portion extending out from the base portion such that the base and wall portions substantially form a right angle, and an aperture or apertures in the wall portion making up at least substantially 50% of the wall portion, the means for controlling cracking formed such that when it is in use it can be positioned such that a cementitious substance prone to cracking can be poured around it and at least partially through the aperture or apertures such that cracks which subsequently form within the cementitious substance will occur at or in the vicinity of the means for controlling cracking.

According to a further aspect of the invention there is provided a method of controlling cracks in a cementitious substance prone to cracking including the steps of:

• • i) obtaining means for controlling cracking as described in any one of the preceding aspects and arranging it at or adjacent a position where it is desired that cracks form in the cementitious substance,
  • ii) arranging a volume of the cementitious substance so that it extends around and at least partially through the wall or wall portions, as the case may be, and
  • iii) allowing cracks to form in the cementitious substance at or in the vicinity of the means for controlling cracking.

Preferably the cementitious substance comprises concrete.

According to a further aspect of the invention there is provided a method of controlling cracks in a cementitious substance prone to cracking including the steps of:

• • i) obtaining a crack controller wherein the crack controller has a base, a wall or walls extending from the base, an aperture or apertures in the wall or walls, and arranging the crack controller in position where it is desired that cracks form in the cementitious substance,
  • ii) arranging a volume of the cementitious substance so that it extends around and at least partially through the wall or walls, and
  • iii) allowing cracks to form in the cementitious substance at or in the vicinity of the crack controller.

Preferably the aperture or apertures make up at least 50% of the surface area of the wall or walls.

DESCRIPTION OF THE DRAWINGS

Some preferred forms of the invention will now be described by way of example and with reference to the accompanying drawings, of which:

FIG. 1 is a transverse cross section view of a concrete crack controller,

FIG. 2 is a side view of the crack controller of FIG. 1,

FIG. 3 is a plan view of the crack controller of FIGS. 1 and 2,

FIG. 4 is a perspective view of an alternative concrete crack controller,

FIG. 5 is an end view of the crack controller of FIG. 4,

FIG. 6 is a transverse cross section view of a straight line connector,

FIGS. 7 and 8 are a side and plan view respectively of a four way connector,

FIGS. 9 and 10 are a side and plan view respectively of a three way connector,

FIGS. 11 and 12 are a side and plan view respectively of a two way angled connector, and

FIGS. 13 and 14 are a side and plan view respectively of a three way T connector,

FIGS. 15 to 18 are perspective and end elevation views of alternative concrete crack controllers.

DETAILED DESCRIPTION

Referring to FIGS. 1, 2 and 3, the concrete crack controller 1 is an elongate section having a base 2 with two elongate side walls 3 and 4 angling upwards from the base to meet one another. The controller 1 is thus hollow and generally triangular in transverse cross section. The side walls 3 and 4 have a series of spaced elongate apertures 5 as shown in FIGS. 2 and 3. As can be seen, the base 2 extends slightly either side of the walls 3 and 4, and the apex of the walls has a vertical extension 6.

When the controller 1 is in use it may be placed base 2 down and a volume of concrete is poured around it. The concrete at least substantially covers the controller 1 and, by way of the apertures 5, passes therethrough. Steel reinforcing (not shown) can also be passed through the apertures 5 if desired. As the concrete sets it tends to crack at or in the vicinity of the controller 1. This controlled cracking may be facilitated by the fact that the body of concrete either side of the controller may have substantially greater mass than the controller and/or the portion of concrete which passes through the controller.

FIGS. 4 and 5 show an alternative concrete crack controller 7 which has a base 8 and an upwardly extending wall 9. The base and the wall are substantially in an inverted “T” shape. As shown, the controller 7 has a series of spaced elongate apertures 10. The alternative crack controller 7 is used to control concrete cracks in much the same way as that mentioned previously, that is it is placed base 8 down and concrete is poured around and through it. Reinforcing steel may also be passed through the apertures 10. Cracks which form in the concrete tend to occur at or in the vicinity of the controller 7 given that it creates a line or lines of weakness in the concrete.

Preferably the controllers 1 and 7 each have small apertures in their base 2 or 8 to enable it to be fixed to an underlying surface if desired. Preferably these bases 2 and 8 are substantially flat so that the controllers 1 and 7 can be more readily leveled if need be.

In the case of the first mentioned controller 1 the triangular shape formed by the walls 3 and 4 and the underlying portion of the base 2 give a measure of strength and stability—eg to resist undesired lateral movement of the walls.

The controllers 1 and 7 may be formed from any suitable material, for example from steel, plastics, or resinous materials generally.

When the controllers 1 and 7 are in use it will in certain instances be desirable to connect them to other such controllers 1 and 7 respectively. To achieve this they may be used with suitable straight line, angle, or “T” joints as needed. FIG. 6 shows a straight line connector 11 which can be used to join two of the first mentioned controllers 1. More specifically, two crack controllers 1 may fit onto the connector 11 as a sleeve, each at an opposite end of the connector 11. The connector 11 may have a lip 12 at each end to restrict the extent to which it can fit inside the crack controllers 1.

FIGS. 7 and 8, FIGS. 9 and 10, FIGS. 11 and 12, and FIGS. 13 and 14, show various other connectors which may be used with crack controllers 1 as described with reference to FIGS. 1, 2 and 3. In each case the crack controllers 1 fit as a sleeve onto the connectors. Preferably each of these connectors has an aperture or apertures so that concrete or the like can enter inside and/or through them.

Optionally the crack controllers 1 and 7 and the various connectors described above are formed from 2.0-3.5 mm (or preferably from 2.5-3.0 mm) gauge steel or plastics. The gauge of material used may be selected to match a desired expansion joint size.

Preferably the apertures 5 and 10 in the crack controllers account for approximately 50% or more of the side walls, and more preferably 52% of these.

It will be appreciated that at least some embodiments of the invention enable one to create controlled expansion joints in a body of concrete or the like. The joints may correspond to the positioning of the crack controller beneath the surface of the concrete.

FIGS. 15, 16, 17 and 18, show crack controllers 13, 14, 15, and 16 in accordance with alternative embodiments of the invention. Each figure shows the respective crack controller 13, 14, 15 or 16 in both end elevation and perspective. Each of the crack controllers 13-16 are adapted for various applications, for example for the corners of concrete wall panels to control cracking therein, or to control cracking at floor level. Concrete may be applied to the controllers 13-16 by way of a spray method or any other suitable means.

As shown in FIGS. 15, 16 and 18, the controllers 13, 14 and 16 each have two V shaped end portions and an intermediate connecting wall portion. The wall portions have apertures to enable concrete or some other cementitious material to pass therethrough. In the case of controllers 13 and 14 the apexes of the two V shaped end portions are oriented in the same direction and are connected to their wall portion at their apexes, either at the internal or external part of the apexes as the case may be. In the case of the controller 16 the apexes of the two V shaped portions are oriented away from one another and are interconnected by their wall portion at the internal parts of such apexes. As shown in FIG. 17 the controller 15 is in the form of a right angle, one arm of the angle being a base portion, and the other being a wall portion having apertures therein. Preferably with all of the controllers 13-16 the apertures thereof make up at least substantially 50% of the surface area of the wall portion in each case.

While some preferred forms of the invention have been described by way of example it should appreciated that modifications and improvements can occur without departing from the scope of the appended claims.