and Other Helix Fixings Products
Material: 8mm HeliTie Bar No Points | Lengths 400mm to 900mm
Originally developed in conjunction with British Rail, this method of pinning delaminated rings in masonry arches has now become widely accepted as a simple and economic solutions. CemFix are also used in standard construction repair techniques for bonding across cracks in masonry and as a restraint for bowing solid walls.
The 8mm diameter austenitic grade 304 stainless steel helical reinforcing bar is combined with a unique formula of pumpable, thixotropic, non-shrink cementitious grout, HeliGrout 25. As the installation of the CemFix is via a 12-16mm diameter drilled hole, the potential disfiguration to the structure is considerably minimised, and the installation time is greatly reduced. This is especially important where access and working times are restricted.
Because of the method of installing CemFix it is not possible to perform random non-destructive site tests. Bond strengths can, however, be checked prior to the full installation programme. An overlong tie can be installed as normal leaving a short length (50-75mm) proud of the surface. A lightweight test unit can then be used to determine the tensile loading. The full cure time for the cementitious grout is 28 days, but testing can generally be performed after 10 days. To check the flow of the grout into any voids requires destructive testing methods and is normally only performed in critical situations.
The Only restriction on the length of tie that may be fixed is the length of hole that can be drilled. In general terms this is restricted to 1.5M. The insertion hole is varied from 12-16mm diameter and is formed with a SDS hammer drill. To ensure a good bond strength between the cementitious grout and the substrate it is necessary to thoroughly wet the drilled hole before the installation of the Cemfix.
Installation of the tie is performed very simply by the use of a manual or mechanically aided installation gun kit. The cementitious grout is installed under pressure and flows readily under light pressure to fill any voids in the masonry structure.
The compatibility of the cementitious grout and the 8mm helical stainless steel bar have been assessed and approved to work together. While the Heligrout 25 is a high strength material, >25 Newtons per mm2, by incorporating the flexible and elastic helical bar the treated structure is permitted a degree of movement. From early tests it was found that too high a strength grout did not allow natural movement of materials within the structure and further cracking occurred. The main purpose of the grout is to bond the HeliTie Bar to the substrate and have similar characteristics as the surrounding substrate; in essence, to restrain but not to stiffen the masonry to the point of further cracking or failure.
Experience has shown that allowing continual but controlled movement in a structure is very beneficial to its long term life. A heavy duty anchor that attempts to stop movement altogether has been shown to store up potential problems, and may even end in a sudden and catastrophic failure.
HeliGrout 25 is formulated to produce a thixotropic material that flows readily under pressure, allowing rapid void filling in deep holes, but will not drip if used overhead. The initial cure time is very rapid and a non-shrink agent ensures that a good even bond is achieved. It is supplied as a complete material in either 6 litre or 3 litre packs offering a consistent mixture time after time.
No extra material is required and a clean mixing bucket is available for each mix. The working life of the material can be extended by re-agitation and will be in excess of 30 minutes.
The helical bar is a grade 304 stainless steel material with a very pronounced profile to ensure a good bond with the cementitious grout. Being stainless steel the issue of ‘coverage’ requirements does not arise.
• Minimal disfiguration to structures
• Quick and easy to install
• Cementitious grout fills any voids
• Lightweight installation equipment
• Strong yet flexible fixing
• Range of lengths to suit application