Concrete Repair and RestorationCategories: Building Restoration
We restore concrete finishes on high rise and heritage buildings, parking garages, and strata and commercial buildings in the greater Vancouver area.
We do everything from small isolated concrete repairs to large-scale projects that involve forming and placing of concrete hundreds of feet in the air. We’re experienced at carrying out complex restoration projects that require significant planning and organization. Many of our restoration projects are done under the guidance and inspection of engineering consultants.
Our experience and commitment to customer service and safety allows us to deliver quality workmanship and timely completion with minimized disruption. We’re committed to accomplishing our work with the safety and convenience of the building occupants and neighbours in mind.
We can also help by providing building surveys to assess the scope and cost of needed repair, and by doing concrete scaling, where we remove loose concrete which may be in danger of falling.
Many of our projects combine concrete restoration with other of our services including washing, sealant renewal, crack repair, waterproofing membranes, concrete sealers, metal flashings, and painting.
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Why does concrete need repair?
Concrete is one of the most durable of building materials, but all concrete is permeable. It has tiny pores that allow moisture and air to get in and out. This moisture and air is a potential threat to the structural steel in the concrete, called “rebar” (which is short for “reinforcing bar”).
The rebar has some built-in protection that is provided by the concrete. Concrete is naturally alkaline and thus produces a film of oxides and hydroxides on the surface of the reinforcing steel. This durable and self-replacing film protects the reinforcing bar from air and moisture that migrate through the pores in the concrete. It can last for hundreds of years.
So what is the problem? Why might concrete deteriorate and “spall” (delaminate) on your building? The culprit is moisture, or more specifically, certain kinds of moisture.
Moisture from rain penetrates the surface layer of concrete. This is not, in itself, a problem. The damage comes when the concrete is attacked by either chloride – that is, the salts in the air combined with moisture (typical on buildings near the salt water) – or “carbonation” – that is, rain that is naturally acidic. One or both of these culprits break down the protective film surrounding the reinforcing bar. Typically, this happens when the reinforcing bar is too close to the surface of the concrete. Moisture will penetrate and affect the rebar if it does not have a sufficient layer of concrete to protect the steel. Optimally the rebar should have a 1” concrete cover to protect it.
When acidic or salty moisture and air get at the rebar, the result is that the rebar oxidizes, or rusts. And as the rebar rusts it expands – up to ten times the volume of the steel consumed. The pressure of the expanding bar spalls or breaks away the surrounding concrete. It’s like that bottle of beer you forgot in the freezer: the expanding volume pushes off the cap or breaks the bottle.
The rusting and weakening rebar and the resulting loss of concrete weakens the structural strength of the concrete and can cause a safety hazard from falling debris.
How we repair concrete
Our typical repair process is as follows:
- We identify the areas needing repair by sounding them out. (The delaminated areas will sound hollow when tapped with a hammer.)
- We chip out – usually with electric hammers – the delaminated concrete. If there is rebar that has significant exposure, we chip out the concrete in behind the rebar.
- We “saw cut” the edges around the patch. This step allows us to do a neat, sound patch with good repair strength and no thin “feathered” edges that will later fail.
- We mechanically clean the reinforcing steel, removing loose rust and scaling. If the rebar has been compromised by rust, we splice in new rebar with proper overlaps.
- We moisten the patch area, apply a slurry coat by brush to the reinforcing steel and the area being patched, apply the polymer modified patch material, and trowel it out. (In the picture below we’ve formed the bottom of the patch to maintain a consistent finish with the surrounding area.)
- Protective coating: when the repair work is done, we suggest an appropriate coating or sealer to protect the concrete against future damage.
Concrete crack repair
We often repair cracks in concrete or stucco as part of a restoration or painting project.
If the cracks are merely hairline, that is, the width of the crack is less than that of a credit card thickness, we often stripe coat the cracks with one or two coats of an elastomeric coating. The elastomeric coating bridges the crack and remains flexible if the crack continues to have minor movement.
Wider cracks with movement need to be dealt with differently. Typically, the procedure we follow is to grind out the cracks with a grinder. They are ground out to a depth of about ½” and a width of ½”.
Following this, we use a bond-breaker at the bottom of the crack (usually silicone or wax) to give us two-sided adhesion. We typically fill the crack with a urethane sealant, such as NP1. This will remain flexible, and if the crack continues to have movement, this sealant will flex with the movement.
After applying the sealant to the crack, we tool off the product to leave it flush with the surface.
In some applications, where the cracks are no longer moving, we fill the cracks with cementitious filler. The advantage of this option is that the cracks are less visible, since the filler can be filled flush and then be ground afterwards.
Visit Our Work project pages to see some of our work in action, and let us show our expertise to you.
Contact us at [email protected] or 604-882-5155 to review your property.Contact Us