There’s always a chance for thermal cracking to occur, but there are some things you can do to help reduce your risks. We have been tasked with replacing several thousand yards of concrete due to several key reasons:
- Using the wrong type of cement mix for mass concrete (namely using too much Portland cement).
- Too much heat trapped in concrete surfaces; concrete surfaces (interior or exterior) exceed ambient temperatures
- Applying concrete when it’s cold can cause contractors to add hot water to concrete mix so that it sets faster. This increases the risk that the concrete mix becomes warmer than ambient temperatures while it sets.
- Too much Portland cement in the mix.
What is Thermal Cracking?
Thermal cracking occurs due to drastic temperature fluctuations in interior and exterior concrete surfaces. It can also occur if concrete reaches 10 degrees F hotter than air temperatures. As concrete temperatures further exceed ambient temperatures, the risk for thermal cracking continues to go up.
Here are some ways to help prevent and control thermal cracking.
1. Use Less Portland Cement
Cement mixes that are overly heavy in Portland cement have a greater chance of resulting in thermal cracking. That’s because Portland cement generates a lot of heat. Adding something to offset Portland cement content can help, such as slag cement or class F fly ash. The goal is to use cement mixes that are designed to produce less heat-of-hydration.
It’s crucial to work with an expert consultant when planning and installing mass concrete because a specialized type of concrete is necessary for success. Speaking of mass concrete…
2. The Right Mix for Mass Concrete
Using too much Portland cement is never a good thing if you’re trying to prevent thermal cracks, especially when mass concrete is concerned. Portland cement generates too much heat for concrete elements that measure 4-6 inches thick, also known as “mass concrete.” As a result, temperature fluctuations are sure to occur and heat generates faster than it can escape—causing concrete temperatures to fluctuate drastically from ambient temperatures. AKA: the perfect recipe for thermal cracks to form.
Mass concrete mixes contain as much as 50% Portland cement replacement when supplemented with fly ash. Mass concrete mixes contains as much as 75% less when Portland cement is substituted with slag cement.
3. Add Cooling Pipes
For the most part, temperature fluctuations can be greatly reduced by using the right cement mix. In some cases, it’s necessary to install cooling pipes beneath mass concrete surfaces to prevent conditions that cause thermal cracking.
4. Use Insulating Blankets
If there’s any risk ambient temperatures will dip below concrete surface temperatures it’s important to cover surfaces with insulated blankets right after installation. This stops any one area from decreasing temperature too fast. Blankets should remain on surfaces until the “highest temperature of the casting decreases to safe levels.” It’s important to leave blankets on until there’s no risk of thermal shock due to low ambient temperatures.
5. Cooling Ready-Mix in Hot Weather
Mixes applied in hot weather can be cooled with liquid nitrogen or ice to help slow the initial reduction in early hydration temperatures.
6. Use Electric Temperature Sensors
When installing mass concrete the use of electronic temperature sensors can be used to determine the hottest and coldest segments of concrete.
7. Turn to Kleenco Construction, #1 in Tennessee
When it comes to preventing thermal cracks, your concrete contractor plays an important role. Rest assured, no one knows commercial concrete like Kleenco. From mass concrete to smaller commercial projects, we have the tools, knowledge, and professionalism to get the job done right every time.
We do everything within our power to keep ambient temperatures and concrete surfaces at the right temperatures for success. Trust us to stay on top of the latest weather reports and carefully prepare ready-mix and ground temperatures for success. Contact us today for a quote.