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Plastic Shrinkage Cracks- The Lesser-Known Type Of Concrete Cracks

Have you ever seen those long, thin cracks that zigzag their way across a concrete driveway, patio, or sidewalk? You know the ones – they always seem to show up right when you put your new shoes down on them and cause you to almost lose your balance. These pesky concrete cracks are an eyesore that cost your property its curb appeal.

Let’s get into the details now!

What are Plastic Shrinkage Cracks?

As the name suggests, plastic shrinkage cracks occur when concrete is still plastic. That’s when the water to cement ratio is still high, and the concrete hasn’t had a chance to set properly.

These cracks in concrete mainly occur on flat, horizontal surfaces like a concrete driveway. However, beams, rooftops, and other vertical surfaces are not exempt from plastic shrinkage cracks. They can appear on any type of concrete, whether pre-cast, air-entrained, or high-strength concrete.

The characteristics of plastic shrinkage cracks are:

  • They’re usually less than a quarter inch in width.
  • They can be either straight or jagged.
  • These cracks in concrete surfaces run parallel to each other, roughly 1-3 feet apart.
  • Plastic shrinkage cracks are shallow.
  • They don’t intersect the perimeter of the slab.

Factors Influencing Plastic Shrinkage Cracking

Plastic shrinkage cracking is commonly linked with hot weather concreting. Still, it may happen at any time due to rapid moisture loss. Rapid water loss during the plastic state causes the concrete to contract and results in plastic shrinkage cracks.

Other conditions that may cause cracks in concrete are:

  • The concrete temperature
  • Ambient air temperature and humidity
  • Wind speed above five mph
  • The rate of concrete placement/finishing operations
  • Use of plasticizers or admixtures

All these factors work together to create the cracks. When any one element is out of balance, it can cause problems. That’s why plastic shrinkage cracks are more common in hot, dry weather. The ideal conditions for these cracks in a concrete driveway are a high concrete temperature, low relative humidity, and moderate wind speed.

Addressing Plastic Shrinkage Cracks

These concrete cracks are unsightly but not hazardous. They do not impair the strength or stability of the concrete. However, they can be challenging to repair and cause problems if left untreated. The best way to avoid plastic shrinkage cracks is to prevent them from happening in the first place. You can do this by controlling surface evaporation.

There are a few ways to do this:

  • Use plastic sheets or wet burlap bags to cover the concrete during curing.
  • Keep the area around the concrete cool with fans or by sprinkling it with water.
  • Erecting temporary windbreaks around the concrete can also help.

You can also try evaporation retardants, which are sprayed on the concrete surface and slow down evaporation. Plus, if the curing time is reduced, plastic shrinkage cracks are less likely to form.

Conclusion:

Plastic shrinkage cracks, although superficial, can cause structural damage if left untreated. As mentioned, for these concrete cracks, what works best is prevention. Therefore, you must work with an experienced contractor who can adequately mix and place the concrete and take measures to prevent harsh evaporation.

The expert concrete paving services offered by Surface Solutions LLC, serving Cambridge, MD, are your best bet for all things concrete.

Schedule a free estimate now, and let us sweep you off your feet with our top-notch concrete work!