The underlying reason expansion joints can become a problem in floors is for one of many reasons.
1. The joint is a weak area on the floor. Over time the wear from static point loading of solid wheeled truck traffic breaks off the edges of the concrete slab. These edges are known as the arris shoulders. As the edge breaks down a small ‘jolt’ as a truck passes then amplifies and the damage becomes worse. This is a self-perpetuating situation and the hole becomes deeper.
2. There is subsidence under one slab which causes it to drop. This creates a higher level on one side and is therefore a trip hazard and causes damage to pallet trucks and their content. As the pallet truck moves from one slab onto the slightly higher slab it ‘bangs’ the arris and damages the concrete, the bearings and wheels on the truck and the contents of the pallet.
The more substantial the hole then the greater and the more extensive the expansion joint repairs need to be. If the expansion joints require simply re-sealing then the debris and edges are prepared using a vacuum assisted grinder to clean out the joint first and create a new right angle edge. A foam ‘backer rod’ is inserted into the joint to support the jointing compound as it cures. This backing rod is pushed down into the joint to a depth below level of the same distance as the width of the joint, i.e. about 10mm. The inside surfaces are surfaces are primed with a resin and the joint is filled with one of two compounds. The product chosen is dependant on performance and budget. Re-Joint is an Epoxy and so therefore a two-part mix. So you have to mix Part A with part B and pour the pourable grade or trowel/spatula the V grade into the joint. The curing occurs throughout the material at the same rate over a short period of time. Super-Joint is a single pack foil sausage packed product. This is extruded into the joint with a gun and levelled with a spatula. Being single pack it starts curing on contact with air. Because of this it skins over quite quickly but if it is quite thick it takes a long time to cure through to the middle. Re-Joint is tougher and more chemical resistant than Super-Joint. Re-Joint is more difficult to use. Super-Joint works our much cheaper per linear meter than Re-Joint for the same dimensions within any given joint.
If the damaged joint is much more substantial then the concrete is cut back and excavated to a neat clean solid line. The larger void is epoxy primed and in filled across the whole surface with an epoxy mortar and levelled flat from one slab to the other slab by trowel. This is left to cure hard and will become 72 Newton’s in compressive strength. Once cured a new smaller 5mm to 8mm joint is re-cut to allow each slab to move independently with temperature change and and traffic. This new joint is in filled with the flexible jointing compound as described above. Please contact us if you require any further information about our expansion joint repairs.
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