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Delivery systems for resin
bonded anchors
Written by John Burch, 2K polymer systems ltd
For the Construction Fixings Association
The use of a chemical resin to bond continuously threaded rod, deformed reinforcing bar and internally threaded sockets is a
well-established method of producing reliable fixings and structural connections intoconcrete, with major advantages over
mechanical fixings in that they offer stress free anchorages, accommodate a wide range of sizes and performance and work
in the widest range of substrates.
Over the years a variety of packaging and delivery systems has been developed, each new system usually being an
improvement over its predecessors; resulting in a broader range of applications and, in some cases, much cheaper unit
costs. In this article John Burch explains the development of the various systems and their advantages.
Bulk mix systems ing techniques is important for all systems but the resin, allow any quantity of bonding resin
The earlier resin systems were invariably of the spinning action of capsule systems means to be placed in the hole and also bring major
the “mix and pour” type, where the that any dust adhering to the sides is drawn economies to the fixing process. Cartridge
components of the resin were (and still are) into the mix making them less sensitive to capacities vary from as small as 150ml, to
mixed and then placed, either by pouring poor hole cleaning. Thorough cleaning should cater for small jobs, up to 1,400ml
under gravity or by pumping, into the prepared always be employed on all systems. pneumatically powered systems to cope with
drilled hole, followed by insertion of the “Hammer-in” capsules are a development large numbers of anchors such as starter bars.
threaded rod or rebar. of the glass capsule system for rebar anchoring In these systems the components of the
The chemistry involved in these resin in which the rebar is hammered through the bonding resin are contained in separate
systems demands good control of the mixing special capsule pulling the catalyst through the compartments, traditionally either one inside
process, especially for pure Epoxy resins which resin components thus forcing them to mix. an outer rigid cartridge or as two side-by-side
require molecule to molecule contact to Although the rebar may be literally cartridges. By using a suitable manual, cordless
achieve complete curing. Ensuring that the hammered in using a large club hammer most or pneumatic gun two pistons extrude the
components are mixed in the correct manufacturers provide adaptors to harness the contents of each compartment from the
proportions is best managed by the mixing of power of drilling machines. The lack of cartridge into a special mixing nozzle, from
only complete packs of the product, the spinning action means there is no tendency to where the mixed product is injected directly
system of European Technical Approvals allows draw any residual dust into the mix so into the hole.
only this approach. This full-pack mix thorough cleaning is vital. Because the resin is mixed only when it is
requirement may not present a difficulty when For capsule systems it is necessary that the being delivered any unused material still
installing a significant number of large anchors capsule, the size of the drilled hole and the within the cartridge can be kept for later use,
but in the case of smaller fixings, these fixing rod are matched, and frequently this and any waste is restricted to that contained
systems become both inconvenient and results in limiting the depth of anchorage to within the mixing nozzle. Some powered guns
uneconomic. Additionally, the open handling of one value for each diameter. Usually the meter the exact amount to eliminate wastage
chemicals may introduce health and safety anchorage depth is optimised to match the from over filling.
issues, with their attendant costs. strength of the resin/concrete bond with that One of the advantages that resin bonded
of the anchor rod. However, for specific anchors have over other fixings is that they
Capsule systems applications requiring higher loads two avoid the production of high, localised crushing
The need for smaller-scale packaging led to capsules may be used to double the forces, and this advantage becomes even
the development of the encapsulated type of embedment depth with high strength rods. more pronounced when fixing into low
product, where all of the component Capsule systems provide exactly the correct strength bricks and aerated or lightweight
chemicals are contained in separate amount of resin for use in concrete but aggregate blocks.
compartments within an outer glass tube, a masonry - with poorly filled mortar joints, Injection systems, with their ability to
soft plastic skin or a foil tube. perforated bricks and hollow blocks - demands deliver as much bonding material as is
In “Spin-in” versions the capsule is inserted another solution. This, together with the need needed, can be used most effectively in
into the prepared hole, and the fixing is to provide specially shaped anchor rods, conjunction with perforated sleeves (mesh
mechanically rotated and driven through the different sized capsules for each rod diameter sieves) to provide fixings that have optimum
capsule, rupturing the capsule and its and spinning adaptors (sometimes provided performance into voided substrates such as
compartments, and mixing the components free), opened the door to the introduction of perforated bricks and hollow blocks.
in-hole. One aspect common to all resin injection systems.
systems is the need to remove all dust from Cartridge types
the hole sides before introducing the resin. The Injection systems Since the introduction of the cartridge as an
use of a brush as well as blowing or vacuum- Injection systems, using cartridges to deliver all-in-one means of supplying,
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