Concrete surfaces can be found in a variety of situations, often chosen not just for its strength but for ease of use when laying. Concrete may have to withstand tough environments such as year-round exposure to weather and UV light, and heavy use in workplaces where foot traffic and machinery can cause damage.
Concrete floors are commonly found in warehouses, factories and workshops, and outside as garage forecourts, loading bays, car parks and children’s play areas at schools and parks.
Walls made from concrete may be used in extensions on commercial and industrial buildings but also as low walls where paths may cut through higher ground, such as outside arenas and public buildings for a gentler approach for foot traffic.
Concrete is also used for creating steps adjoining outdoor areas at different heights, as well as slopes to make these areas accessible by wheelchair users.
Follow Sika’s simple seven-step process below to ensure that concrete repair works are carried out safely, to a high standard, and will deliver lasting results.
Sika Concrete Repair Products
- Concrete floor repairs
- Concrete crack repairs
- Protective coatings for steel
- Grouting and fixing
At the outset of all projects:
- Ensure you use only clean potable water
- Make sure tools are clean and well maintained
- Remove only concrete as instructed by supervising officer or qualified engineer
- Consult product data sheets before starting
Things not to do when repairing concrete:
- Never contaminate mixture with other chemicals
- Do not mix powders from different products
- Be careful not to add more water than recommended
- Don’t mix and apply product in direct sunlight
Step 1: Substrate Preparation
Mark the defective concrete and then remove, according to the size of the affected area.
For small patch repairs, a hammer and chisel will probably be sufficient.
For slightly larger areas, use a hammer drill and for even larger areas the use of a high-pressure water jet might be necessary.
Remove concrete to a minimum of 155mm behind the main bars, cutting side to a minimum of 90° to avoid undercutting and maximum of 135° to reduce debonding around edges.
The substrate should be sound with no loose material before you continue; inform a supervisor immediately if there are any cracks in the substrate.
Step 2: Reinforcement Preparation
Remove all tie wires, mortar/concrete, rust/scale and any other loose material.
There are three removal techniques:
- Steel wire brush or hand / power tools – this technique is applicable only in carbonated concrete and under environmental constraints where techniques 2 and 3 cannot be used.
- Abrasive blast cleaning – if chlorides are present reinforcement should be cleaned with water afterwards
- High pressure water jetting – 1,100 bar minimum
Step 3: Reinforcement Corrosion Protection
Apply two 1mm thick layers, allowing time for the first coat to harden before applying the second coat.
Allow application to dry before applying repair mortar.
Corrosion protection can be applied using a hopper spray for large applications or using brushes to smaller applications. In this instance, use two brushes simultaneously to ensure full application behind the bars.
Step 4: Bonding Primer (if specified)
Wet the substrate before wiping away excess water, using a sponge for small areas of air pressure for larger areas.
To apply the primer, use either a brush or hopper gun. Be sure to point the gun at different angles on the surface to ensure even application behind the bars.
Step 5: Repair Application
If bonding primer has not been applied, wet the substrate as directed in step four.
When repairing by hand, press the repair mortar firmly into the repair area using a trowel and/or hand. Apply a second layer when the first layer is dry if the application depth exceeds the product’s maximum layer thickness.
Profile the surface and finish with a trowel. Finish with a wooden or PVC trowel for best results. Do not spray additional water over the surface.
When repairing by spray, point the nozzle 200mm to 500mm from the surface.
Again, finish with a wooden or PVC trowel for best results. Make sure voids are filled behind the bars. If second layer is required, surface should not be too smooth.
Step 6: Smoothing Mortar
To prepare the surface, wet and clean with water (180 bar). Then smooth the mortar using a toothed trowel, moving vertically. The trowel should sit approximately 45° to the surface.
When the first layer is hard, apply a second layer.
Smooth the surface using a wooden trowel after the product has set – anywhere between 25 minutes and 4 hours.
Step 7: After Application
Curing will protect the repair from frost, wind, rain and sun.
Apply as soon as possible after application to avoid the surface cracking.
Curing can be carried out using plastic sheeting, fabric and water of other membranes.
- Concrete Repair – Fixing Concrete Cracks
- An Overview of Concrete Floor Sealers
- SikaFloor PurCem Polyurethane Concrete Flooring Systems