Tag Archive for: Plastic Shrinkage Cracking

How to Minimise Plastic Shrinkage Cracking

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Plastic shrinkage cracking occurs as a result of how fast the concrete surface dries in comparison to the rest of the concrete. According to concrete suppliers in Brisbane, plastic shrinkage tends to form when the concrete is still plastic. Plastic shrinkage may take place any time throughout the year whether the weather is cold, hot, windy, or low humid. It is worth noting that plastic shrinkage cracks take place in an arbitrary manner or they will be parallel to each other. Most often these cracks are straight and their length may vary between 2 m to 25mm. They will hardly occur around the edges of a slab. The cracks create a weakness in the concrete and possess the capacity of further widening as a result of subsequent thermal movement.

6 Important Tips to Minimise Plastic Shrinkage Cracking

Described below are some important tips to minimise plastic shrinkage cracking in concrete:

1. You should erect temporary windbreaks:

When the wind blows at a higher velocity, it may significantly impact the water evaporation rate from the concrete being placed. It will likely cause plastic shrinkage cracking of the concrete. In order to prevent this, you may opt for erecting temporary windbreaks. This will help in reducing wind speed at the surface of the concrete.

2. Sunshades:

When you are constructing concrete slabs, the option of providing sunshades over the concrete slabs will prove helpful. It will aid in controlling and bringing down the surface temperature of the slab.

3. Effective placement timing:

During extreme hot weather conditions, it is not ideal to erect the concrete during the afternoon. If you do so it may cause plastic shrinkage cracks as a result of water loss. Therefore, it is ideal to schedule concrete placement in the morning or evening time, this just allows you more control over the concrete temperature.

4. Opt for fog sprays:

During scalding hot weather conditions, the wind tends to be extremely hot and unbearable. You should opt for fog sprays to spray fog in the hot air on the concrete surface as it helps to reduce the evaporation rate from the concrete surface. You should spray fog towards the opposite direction the wind is blowing.

5. Try dampening subgrade:

When the construction of concrete pavement is underway during hot weather conditions, you should dampen the subgrade as it is responsible for water absorption from the concrete, however, it is important to note that subgrade should never be excessively damp.  Steel suppliers in Brisbane will help you minimise plastic shrinkage cracking.

6. Use evaporation retarder:

As we are aware that surfaces may dry earlier than anticipated when the evaporation rate is higher than the bleeding rate. You can consider spraying an evaporation retarder like aliphatic alcohol on the concrete surface. These types of products help in forming a fill on the surface that reduces the evaporation rate of water. It also provides time for all the bleed water to move towards the surface. In extremely hot weather conditions, you may have to consider re-application of evaporation retarder.

Conclusion:

The above ways will help you minimise plastic shrinkage cracking. You may get in touch with reinforcing mesh in Brisbane to tackle the situation effectively. Do not forget to avail adequate manpower, devices, and supplies to ensure that concrete can be placed and finished instantly.

What is Plastic Shrinkage Cracking?

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Plastic shrinkage cracking refers to the cracks formed when concrete has not yet set. It occurs when the concrete is in the form of plastic only. The main cause behind crack formation is the rapid drying process. Cracks can be seen the next day after the finishing operations. Plastic shrinkage cracks can form randomly or can be roughly parallel to each other. Concrete Brisbane gets weak due to these cracks and therefore expand.

What Causes Plastic Shrinkage Cracks?

The basic reason behind the occurrence of cracks is the higher rate of evaporation of moisture from the surface. When the evaporation rate exceeds the moisture supplied to the concrete, cracks are formed. The concrete surface dries out because of the lack of moisture on the surface and hence it cracks.

Water is lost in the following two ways:

  1. Drying from the top: During the placement process, moisture seems to evaporate from the top surface of the concrete, which is also known as bleeding.
  2. Drying from the base: Water can get absorbed in the ground below the concrete slab. This increases the risk of cracking and also the settlement of concrete and mesh reinforcement Brisbane.

There are various environmental factors that affect the rate of evaporation from the surface of concrete, such as wind speed, temperature, and humidity. A combination of all these factors leads to cracking even in cold weather conditions. Also, the concrete mixtures which have a reduced rate of bleeding are prone to plastic shrinkage cracking. Any factor that contributes to a delay in the setting process, leads to cracking.

How to Control Plastic Shrinkage Cracking?

Mentioned below are the tips that will help you in minimising plastic shrinkage cracking in your concrete:

  • Dampen the surface of concrete frequently.
  • During hot weather, mix water with crushed ice or use chilled water.
  • Use windbreaks to reduce the velocity of wind that is coming on the surface of the concrete.
  • Use product substitutes that reduce the rate of evaporation from the surface.
  • Start the curing regime immediately after finishing.
  • Use synthetic or steel fibers to prevent cracking.
  • Accelerate the setting time of concrete.
  • Use fog sprays in dry periods to discharge a fine mist into the air. Fog sprays reduce the rate of evaporation from the surface of mini concrete Brisbane and should be used until curing is applied to the concrete.
  • Cover the concrete with moisture-retaining coverings like polyethylene or building paper sheets.

Reocrete is the leading supplier of concrete and steel reinforcing mesh in Brisbane. We deliver the right grade and consistency of concrete to your worksite at the exact time and day you need. We understand how much of a difference just a 30-minute delay in the compaction of concrete can cause. So, we practice what we preach and deliver exactly what you need!