Steps to Prevent Plastic Shrinkage Cracking: How the New Target Evaporation Rate Solver Can Help

June 4, 2020 Monica Devlin Comments

Are you a concrete contractor plagued by plastic shrinkage and cracking, all while worrying about your reputation, repair work, and expensive litigation?

The Kestrel 5200 Evaporation Rate Solver ensures successful slab curing and prevents plastic shrinkage cracking. When plastic shrinkage cracks occur, associated problems begin to pile up - leaving contractors to deal with the hassle and cost of repairs.

Cracks appear in concrete before it hardens when the tensile stress is greater than the tensile capacity. It occurs within six hours after laying the concrete, leading to plastic shrinkage cracking and plastic settlement cracking.

The cracking of concrete is referred to as plastic because the concrete is still soft and wet, and there is lost water at the surface of the concrete before it has set. Bleeding occurs when the aggregates and binder try to sink to the bottom while the water rises to the top.

When concrete bleeds, a thin layer on the surface evaporates away. If the evaporation rate exceeds the rate of bleeding, it will shrink on the surface while the concrete remains soft below. The cracks then appear in the plastic (known as wet concrete) surface, as in the photo below.

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What Increases the Risk of Plastic Shrinkage and Cracking?

Several issues come into play when it comes to plastic shrinkage cracking. Including low amounts of water and high amounts of paste (binder + water). However, the weather and environmental conditions are also crucial considerations to reduce the risk of plastic shrinkage cracking.

Weather will worsen the risk of shrinkage and cracking when the air temperature is high, and the relative humidity is low. It is also affected by high concrete temperature, wind speed, and sun exposure. They are similar to the same conditions that will give you a sunburn or chapped lips.

While it is impossible to control the weather, there are ten precautionary steps to prevent plastic shrinking and cracking.

These ten steps include:

Put up temporary windbreaks. Since wind velocity affects the evaporation of water, the windbreak can reduce this velocity and prevent shrinkage.
Provide shade. Shading concrete slabs will help ensure that the surface does not get too hot.
Place concrete in the early morning or evening, especially on sweltering and humid days.
Use a fog spray. Fog spray is helpful on hot and dry days when the warm wind is blowing. Spray it into the air in the opposite direction of the wind that is blowing.
Dampen the subgrade in hot and dry weather, because it is liable to water absorption from concrete.
Use an evaporation retarder. The plastic's surface can dry prematurely if the evaporation rate is higher than the speed of bleeding; therefore, an evaporation retarder can reduce the evaporation rate.
Start curing immediately. Make sure you commence curing as soon as you can after finishing.
Accelerate the setting time. Chemical admixtures can accelerate the time of setting, which is ideal for avoiding significant temperature variations.
Add polypropylene fibers into the mix. These fibers reduce cracking by binding to the surface.
Be prepared. Make sure you have the proper staff and equipment to handle the process promptly.

With these precautionary steps and the incorporation of the Kestrel 5200 Evaporation Solver, you will be a step ahead of plastic shrinkage cracking.

What is the Evaporation Solver?

Kestrel can already calculate real-time weather data such as humidity, temperature, and wind speed, all of which are factors preventing plastic shrinkage cracking.

However, the Kestrel Evaporation Rate Solver adds something special. It displays the level of cracking risk based on user-defined weather conditions. It also shows the environmental factors that may need adjusting to prevent plastic shrinkage and cracking, allowing you to implement all of the ten steps provided above.

The solver provides an automatic 10-second average capture of the current conditions on a bright and clear screen. This product is portable and rugged, making it easy to have on a construction job site.

Get the Kestrel 5200 Evaporation Solver for Concrete Contractors

Think of the Evaporation Solver as a small assistant in your pocket, guiding concrete contractors into the best conditions for placing concrete. Bring the entire kit to the job site, which includes the Kestrel 5200 with LiNk, rotating vane mount, portable mini tripod, and extension rod, and a protective hard carrying case.

The Kestrel 5200 Evaporation Solver is an essential investment to ensure that your concrete pour occurs in the best conditions possible, resulting in a quality job without a single crack in sight.

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Monica Devlin