Building concrete structures when the temperatures run high has always been a challenge. Hot and dry weather makes the concrete mixture solidify more quickly, leading to higher early strengths. It can impact the overall durability of the structure and compromise the concrete’s structural integrity leading it to cry.
Too much wind can also be an issue as this can accelerate the evaporation of water from the concrete mixture, creating a host of difficulties. In the end, you end up getting a concrete structure with multiple defects. However, preparing for these challenges and devising smart solutions can help you overcome these obstacles and create a robust and long-lasting concrete structure.
Let’s review the challenges of building concrete structures in hot weather in more detail and how you can navigate your way around hot weather concreting.
Increase in the Rate of Slump Loss
Fresh concrete can lose its workability over time. This is referred to as slump loss. The rate of slump loss can increase when you mix or handle concrete at an elevated temperature. Higher temperatures also magnify other causes that can lead to slump loss. For instance, hot weather can increase the rate of evaporation. This compromises the hydration process necessary for concrete setting.
High-speed wind and low relative humidity also play an important role here.
It’s important to remember that slump loss is an integral part of concrete setting. Otherwise, the concrete can never harden. However, you still need to make sure the concrete mix retains its consistency and workability for a sufficient period to place and finish it properly. At normal temperatures, this process takes place at a regular pace, with the concrete losing its slump and becoming rigid.
However, when you subject the concrete to high temperatures, the rate of slump loss can accelerate. You can manage this in various ways. For starters, you add more water to the concrete and mix it again. While this is a simple solution, it can also create an imbalance in the water to cement ratio of the mixture. Adding too much water here can reduce the concrete’s strength. It can also lead to an increase in shrinkage, causing the concrete to crack. Other problems include acceleration in dusting, scaling, and permeability.
Simply put, while you can counter slump loss by adding more water, you will be compromising the strength and durability of the concrete in the process.
To avoid this, you can:
- Cool the concrete mix and bring it to a lower temperature. This can slow down the rate of slump loss.
- You can review your admixture. These have varying slump retention times or different pot lives. There are a variety of new slump retention admixtures also available. These admixtures are designed to increase the slump of a concrete mixture, allowing you to maintain the slump rate for a given period.
Increase in Plastic Shrinkage and Cracking
Ambient temperatures, high wind, and low relative humidity can also lead to plastic shrinking and cracking. This is primarily because the hot weather and wind can accelerate the evaporation rate of moisture present at the surface of the concrete mix.
To avoid this effect of hot weather concreting, you need to maintain the temperature at a low level and dampen the substrate. You can set up shades and windbreaks to protect the area from receiving too much wind and direct sunlight. It’s also a good idea to use fog sprays. On the whole these settings can increase the humidity, while keeping the air temperature at a low level.
You can also try the following to avoid plastic shrinkage and cracking:
- Use an evaporation retarder. These are monomolecular films that you can apply to freshly placed concrete to inhibit the loss of surface moisture before finishing.
- Consider placing the concrete early in the morning or late in the afternoon when the temperature is low.
- Add fiber to your concrete. This protects it from external stress and prevents it from cracking. Steel fibers are particularly useful for this. They can counteract concrete shrinking and prevent further growth by intersecting through the cracks.
Rapid Concrete Setting Times
As mentioned earlier, high temperatures can also increase the pace of the hydration process, causing the concrete mixture to dry too quickly. This can disrupt the concrete setting time, and the final product is highly prone to cracking and other defects.
You can consider using an admixture to control the rate of hydration. It can slow down the setting time and improve the performance of the concrete. This can counteract the effects of high temperature and rebalance the concrete setting time.
How Else Can You Manage Hot Weather Concreting?
We discussed some of the key challenges that arise due to high temperatures, along with some solutions. Here are some additional suggestions you put to use to protect your concrete structures.
For starters, avoid trying to place excessive concrete than you can finish and cover in a given period to try and meet deadlines. As mentioned earlier, you can install windbreaks to control wind speed whenever necessary too.
Besides this, cover any equipment that comes in contact with the concrete mix with wet burlap. You can also keep it under shade when it is not in use and paint them white. This can reduce the amount of solar heat they absorb and stay cool.
You also want to arrange sufficient labor and equipment to get the concrete placed quickly and efficiently. Any delays in this process can increase the temperature of the mix and accelerate slump loss.
If you are preparing concrete mix batches and keep them cool using liquid nitrogen, ice, or refrigerated water. For better management, you can consider starting the concrete mixing process in the afternoon and place it during the evening to take advantage of lower temperatures.
A few other things you can do include moistening the substrates before you pour the concrete. This can protect the mix from premature water loss. You can also spray on collective piles of concrete to keep them cool.
Once the final finishing process is complete, you can initiate the wet curing process.
Monitor Concrete Setting With SolidSense
If you are trying to offset the effects of hot weather concreting, you can use the wireless systems and sensors by SolidSense to monitor the temperature and humidity of concrete in real-time and optimize the process to prevent slump loss, shrinkage, and cracking. These tools offer highly detailed analytics that make it easier for you to adjust the various variables impacting the concrete setting process to ensure that your concrete structures are strong and durable. Get in touch with us today for a free quote!