Introduction
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 12-16mm 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.
Fixing Details
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 Bond Flex 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 installation gun kit. The Bond Flex grout is installed under hand pressure and flows readily under light pressure to fill any voids in the masonry structure. Full installation details are given in the installation section.
The Materials
The compatibility of the Bond Flex and the 8mm Bar Flex have been assessed and approved to work together. Whilst the Bond Flex cementitious grout is a very high strength material - > 40 Newtons per sq. mm. - by incorporating the flexible and elastic Bar 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 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.
Bond Flex 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 6 litre or 3 litre packs offering a consistent mixture 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 re-agitation and will be in excess of 30 minutes.
Bar Flex is a Grade 304 stainless steel material with a very pronounced profile to ensure a good bond with the Bond Flex cementitious grout. Being stainless steel the issue of ‘coverage’ requirements does not arise.
