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Concrete crazing: identification, prevention and repair

Posted on by EKA Concrete

concrete crazing repair

Laying concrete for a patio, garage or garden path can be a simple and rewarding job. It is only when problems like concrete crazing arise that this easy-going construction material can cause headaches. If your concrete has small hairline cracks, typically arranged in polygon patterns, this is known as ‘crazing’ and is caused by the surface layer setting faster than the underlying concrete. It is not a structural issue, but does give an unprofessional appearance. Taking preventative measures against crazing is the best route to a stress-free patio, but if you have already laid the concrete and it has crazed, there is a neat repair trick to make it disappear.

Concrete crazing prevention

To prevent crazing in the first place, you need to think about mistakes that could cause a weak surface layer of concrete to form. Ideally, a slab of concrete will have the same consistency throughout and will not have been smoothed over too much. Manipulating the surface too often will cause the aggregate to settle and form a strong base layer. This will mean that too much bleedwater rises to the surface and evaporates, forming a weak surface that will crack and craze.

When you lay your concrete, here are a few things to keep in mind:  

  • When the concrete is setting, use a concrete curing compound to prevent the rapid evaporation of moisture from the surface
  • Do not use a steel float as this can close the surface and trap air and bleedwater in the concrete
  • Use low-slump concrete, as high-slump will easily segregate
  • Use a low water to concrete ratio to make a low-slump mixture
  • Do not continue to smooth the surface of the concrete once it is flat
  • Do not sprinkle or smooth neat concrete paste onto the surface

 

Fix your concrete crazing

To rectify concrete crazing you will need an ultra-thin layer of concrete to resurface the slab. This fix doesn’t require the use of gravel or sand; all you need is a bag of resurfacing concrete. These are purchasable from any good builder’s merchant and only requires water. To avoid crazing with this layer, it is advisable to use a curing compound, which will prevent the concrete drying too quickly.

  • Use a broom to remove debris from the concrete you want to resurface; the surface must be dry and free of oil, dust and debris
  • Prepare the resurfacing concrete; it must have a thick, ‘plastic’ consistency and should be able to be poured from a bucket
  • Apply with a trowel and use a wood, resin, or aluminium float to smooth over the surface
  • Spray clear curing compound on the surface to ensure the concrete cures slowly

A bonus tip: overcast days are ideal weather for concrete laying. A dry atmosphere, with little sun to form temperature differences between surface and underlying concrete, is your best chance to nip concrete crazing in the bud.

EKA Concrete supply quality concrete for commercial and domestic purposes. With over 20 years of experience, EKA provide fast and efficient ready mix concrete, foam concrete and concrete pumping services. No site is too big or small, so if you are requiring any concrete services, get in touch with our friendly team today.

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