Remedial Work to Concrete Structures
Concrete Crack Injection/Repair
Injections are a good choice because they help avoid expensive costs of structural repairs and reduce operational downtime. They can be used for all types of leak-sealing applications in concrete, masonry and natural stone structures and are able to form a new permanent watertight seal.
Products – FSC has experience using the following products:
- • Sikadur Crack Injection System
- • ARDEX Concrete Crack Repair
- • Permatech Crack Injection System – Capsules
CONCRETE CANCER REPAIRS
FSC utilise two main techniques to repair structures affected by concrete cancer,
1. Concrete cancer caused by carbonation
Polymer modified repair system – This is a treatment used for concrete cancer caused by inadequate concrete cover over the reinforcement. This leads to corrosion of embedded steel reinforcements, also known as concrete carbonation. All the spalled and cracked concrete is removed to show the steel within, which is then cleaned and freed from corrosion using different techniques.
Once the reinforcement has been restored or replaced, it is then painted with a polymer emulsion bonding agent, such as Fosroc Nitobond HAR. It is then encased with concrete, ensuring cover is maintained according to specified recommendations.
As an extra level of protection, the finished surface of the repair can be treated with a primer such as Fosroc Nitoprime DG, followed by an anti-carbonation protective coating such as, Fosroc Dekguard Elastic, which provide ultimate protection against the ingress of carbon dioxide, oxygen, and water, whilst allowing damp substrates to breathe without blistering.
2. Concrete cancer caused by chlorides
Concrete repair with electrochemical treatment – This treatment is used for concrete cancer caused by structures exposed to marine environments or water spray. Concrete contains an alkaline environment that provides some protection against corrosion. The introduction of chloride and sulfate ions, present in marine environments, will weaken this protection as the water soaks into the concrete, and once the protection is breached, then the corrosion process begins to work on the steel itself.
This repair starts with the removal of chloride-contaminated concrete.
After the defective concrete is removed, the rebar is made corrosion-resistant by the application of protective coatings. It is then encased with concrete, ensuring cover is maintained according to specified recommendations. To reinforce the protection from chloride contamination, a surface treatment in the form of cathodic system can be applied.
Crack Stitching
FSC utilise two main techniques to improve concrete crack repair.
1. Crack stitching using rebar and epoxy
Holes are drilled at 45O angle (or similar) to the crack line and should start and finish at least 200mm from the centre line of the crack but on opposite faces of the wall/structure. Once the preparation is complete and free of dust, reinforcement is placed in the drilled hole and the hole is filled with injectable adhesive such as Hilti HIT-RE 500 V3 EPOXY ANCHOR or similar. Once installed, the reinforcement and epoxy permanently bonds both sides of the crack together
2. Carbon-fibre crack bridging stitch
FSC utilise the Rhino Concrete Crack Lock (CCL), supplied by Ardex which was developed to improve concrete crack repair.
The CCL is made from carbon-fibre and resembles a dog bone with a slender centre cord and two larger circular ends. The CCL is installed by making a single blade-width cut across the crack and drilling two holes along the cut at the appropriate locations. Once the preparation is complete and free of dust, it is filled with an approved ARDEX Epoxy Paste such as ARDEX RA 88 (for vertical applications) or ARDEX RA 142, ARDEX RA 144 or ARDEX RA 146 (for horizontal applications) and the CCL is inserted. Once installed, the CCL permanently bonds both sides of the crack together
Protective Coatings
There are many concrete protective coatings on the market for a wide variety of applications. These include products to increase the durability of the concrete by preventing water ingress and products to seal and accommodate surface cracks.
Products – FSC has experience using the following products:
• XYPEX CONCENTRATE
• XYPEX MODIFIED
• Vandex Concrete Grey
Joint Sealing
Only correctly specified and professionally applied high quality joint sealants will manage to keep your building or structure sustainably tight during its entire lifespan.
FSC has experience with a range of joint sealing options for new and existing joints, which include:
• SILICONE SEALING – for non-porous substrates like metal and glass
• POLYURETHANE SEALING – for porous substrates like concrete, bricks and masonry
• SILANE-MODIFIED POLYMER SEALING – where a wide adhesion range is required like for installations of doors/window
• SIKADUR-COMBIFLEX – allows variable and high levels of movement in one or more directions, whilst maintaining a watertight seal
• ELASTOMERIC EXPANSION JOINT SEALING – used where there is a lot of movement between structures such as bridges & approach slabs
• WATERSTOP or WATERBAR – a centrally placed seal between joints within concrete to prevent water from passing through the joints
• HYDROPHILIC PROFILES AND SEALANTS like SIKASWELL – waterstop which is applied to a construction joint and can swell when concrete is poured against it. They are used in watertight concrete structures for systematic sealing of construction joints.
