AU2798801A

AU2798801A - Rib near insert crack inducer

Info

Publication number: AU2798801A
Application number: AU27988/01A
Authority: AU
Inventors: Daniel Charles Underwood
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-03-14
Filing date: 2001-03-14
Publication date: 2001-09-20

Description

P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT 0000 0.

Name of Applicant: Actual Inventor(s): Address for Service: Invention Title: Details of Associated Provisional Application(s) No(s): DANIEL CHARLES UNDERWOOD DANIEL CHARLES UNDERWOOD

INTELLPRO

Patent Trade Mark Attorneys Level 7, Reserve Bank Building 102 Adelaide Street BRISBANE, QLD, 4000 (GPO Box 1339, BRISBANE, 4001) RIB NEAR INSERT CRACK INDUCER Australian Patent Application No. PQ6225 filed 14 March 2000.

The following statement is a full description of this invention, including the best method of performing it known to me: 2 THIS invention concerns surface crack control strips for the control of crack development during curing of a concrete slab.

In our Patent No. 567093 we describe an elongated strip for insertion into a concrete slab where development of a crack is permissible which strip has a rib which keys the strip into the concrete and prevents its displacement once inserted.

The effect of this is to remove any need to finish the surface of the concrete while allowing the strip to exert its effect on the curing concrete.

The rib was of U-section and rolled into a strip of 18 gauge galvanised steel.

Typical depths of the strip are 25, 35 and 45mm. The straight wall of the strip was 10 about 7mm deep leading to a rib of semi-circular section and 12mm dia. and from *.99 o° 9* there to a straight insertion wall.

9. 9.

In a further version the rib was modified by an alternative forming operation to create a flange projecting at 900 to the wall of the strip. The wall was merely ooo0 displaced to one side of the wall axis to form a double wall thickness flange about 15 6mm wide. Again the flange was relatively close the surface edge of the strip.

Some slabs provided with such crack controllers exhibit minor cracks alongside the strips which customers dislike. This type of crack is shown in Figure 9 9 1 of the accompanying drawings. The cause of these unsightly cracks and a way to prevent them is not apparent because a variety of factors affect the curing process. This fault is most noticeable with 25mm strips used in slabs up to about 150mm thickness: This invention addresses this problem.

3 One aspect of this invention provides a crack control strip for insertion into the face of a concrete slab of the type comprising a strip of metal or plastic which is stiffened across the width by the provision of a rib or flange and is of sufficient depth to exert crack induction wherein the rib or flange lies closer to the inserted edge of the strip than the slab surface edge.

The size of the aggregate is selected by the civil engineer depending upon the properties required for the slab. Slabs of 1 50mm thickness where this invention is most useful has 10 20mm aggregate. Prevention of the objectionable "insertion" cracking appears to depend upon prevention of a cement-rich pocket beside the 10 wall of the strip close to the surface. We suppose this pocket to be caused by the rib barring the movement of the aggregate into the pocket after the strip is inserted.

S-We prefer to have 12 18mm of wall depth above the rib and a rib or flange displacement of about 6mm.

Certain embodiments of the invention are now described by way of example 15 with reference to the accompanying drawings in which: Figure 1 is a section through a prior art diverter showing a drying crack; Figure 2 is a section through a diverter according to the invention; and Figure 3 is a section through a diverter with a flange.

Referring to Figure 1, the site of the cement-rich pocket 2 and the crack 4 is evident. The mid part of the rib 2 is midway along the wall.

In Figure 2 the diverter is 1200mm long galvanised steel strip 25mm deep and 1.2mm thick. The depth of the strip H from the surface edge 6 to the start of 4 the rib 8 is 15mm. The rib is 12mm deep and the insertion edge 10 is 3mm deep.

The rib is rolled in and the rib is of semi-circular section (12mm dia.).

In Figure 3 the rib is replaced by a flange. The aggregate 14 is free to move into the pocket 2.

Whilst the above has been given by way of illustrative example of the present invention, many variations and modifications thereto will be apparent to those skilled in the art without departing from the broad ambit and scope of the invention as herein set out in the appended claims.

*oo *ooo

Claims

1. Crack control strip for insertion into the face of a concrete slab of the type comprising a strip of metal or plastic having an insert edge and an opposed slab surface edge and which is stiffened across the width of the strip by provision of a longitudinal rib or flange, the strip being of sufficient depth to exert crack induction along the insert edge of the strip, wherein the rib or flange lies closer to the insert edge of the strip than the slab surface edge.

2. The combination of a crack control strip inserted into a slab of concrete, strip having an insert edge and an opposed slab surface edge and which is stiffened 10 across the width of the strip by provision of a longitudinal rib or flange, the insert edge being positioned at sufficient depth to exert crack induction in the slab along .i the insert edge of the crack control strip, the rib or flange being closer to the insert 0: edge of the strip than the slab surface edge and the slab having an aggregate mix such that the dimensions of the aggregate and the distance from the slab surface to 15 the rib or flange are so chosen that the dimensions inhibit generation of a cement- rich pocket beside the slab surface edge of the strip. DATE this 1 4 th day of March, 2001 ooooo DANIEL CHARLES UNDERWOOD By his Patent Attorneys INTELLPRO