Cem Flex
Originally developed in conjunction with British Rail, the Cem Flex method of pinning delaminated rings in masonry arches has now become widely accepted as a simple and economic solution.
Cem Flex ties 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 rod is combined with Bond Flex XL, a unique formula of pumpable, but thixotropic, non-shrink cementitious grout.
As the installation of Cem Flex is via a 12 to 16mm diameter drilled hole, the potential disfiguration to the structure can be minimised, and the installation time is greatly reduced - this is especially important where access and working times are restricted.
Performance Requirements
Because of the method of installation it is not possible to perform random, non-destructive site testing. Bond strengths can, however, be checked prior to the full installation program. An overlong Cem Flex can be installed as normal leaving a short length (50-75mm) proud of the surface.
A Target Load Test Unit can then be used to determine the tensile loading. The full cure time for the Bond Flex XL grout is 28 days, but limited testing can generally be performed after 24 to 48 hours. To check the flow of Bond Flex XL grout into any voids required destructive testing methods and is normally only performed in critical conditions.
Fixing Details
The only restriction on the length of Cem Flex 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 for 12 to 16mm diameter and is usually formed with a SDS hammer drill.
To ensure good bond strength between the Bond Flex XL cementitious grout and the substrate it is necessary to thoroughly wet the drilled hole before the installation of the tie.
Installation of the tie is performed very simply by the use of a hand-held grout injection gun kit. The Bond Flex XL grout is installed under hand pressure and flows readily under light pressure to fill and voids in the masonry structure. Full installation details are given overleaf.
Special Features
- Quick and easy to install.
- Cementitious grout fills any voids.
- Minimal disfiguration to structures.
- Strong yet flexible connection.
- Lightweight installation equipment.
- Corrosion-resistant materials.
Installation Procedure
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- Drill a 12 to 16mm diameter hole to the nearest depth.
- Blow out any debris
- Thoroughly wet the hole
- Insert the grout gun nozzle to the bottom of the drilled hole and pressure inject the Bond Flex
- Using the Cem Flex Insertion tool, push the Cem Flex tie into the grout-filled hole.
- Remove any excess Bond Flex cementitious grout and finish the hole in the desired manner.
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Materials
The compatibility of the Bond Flex XL and the 8mm Cem Flex have been assessed and approved to work together. Whilst the Bond Flex XL cementitious grout is a very high strength material - ≈ 40 N/mm² - by incorporating the flexible and elastic Cem Flex the treated structure is permitted a degree of movement. Experience has shown that allowing continual but controlled movement in a structure is very beneficial to it's 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.
Bond Flex XL cementitious grout 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 3 or 6 litre packs offering consistent mixtures time after time.
The contractor does not need to add any extra material and has a clean mixing bucket for each mix. The working life of the material can be extended by reagitation and will be in excess of 30 minutes.
Cem Flex is a Grade 304 austenitic stainless steel material with a very pronounced profile to ensure a good bond with the Bond Flex XL cementitious grout. Being stainless steel the issue of 'coverage' requirements does not arise.
Standard Details
