Hot weather and humidity can pose a challenge when pouring concrete, especially when you’re working on patios, pathways, slabs and other outdoor projects. Here are a few tips to help you beat the heat and get your project done right.
For starters, use a large-sized aggregate in your mix if you know that you’ll be pouring in high heat conditions. This will reduce the chances of rapid drying, crusting and plastic shrinkage during placement.
Temperature
Temperature plays an important role in concrete curing, and the right temperature can make a difference in the final product. Hot temperatures can lead to a variety of problems with concrete, including curing delays, cracking, and strength issues.
Cold weather can also have a significant impact on the concrete, especially when freezing occurs within the first 24 hours of pouring. Fresh concrete can lose 50 percent of its initial strength when frozen, and ice build-up can lead to problems with water retention, corrosion, and deterioration of the finished concrete.
The ideal temperature for setting and forming concrete is between 10 and 15 degrees Celsius (50 and 60 degrees Fahrenheit). When it is too cold, the chemical reactions needed to set and strengthen the concrete stop.
During the pouring process, you must keep the concrete and tools from becoming too cold. You can use insulated concrete blankets and other methods to help maintain a safe and warm environment during the pouring process.
You should use a thermometer to track the temperature of the concrete and your workers during the pour. Check the temperature several times over a 24-hour period to ensure that it stays above the required 50 degrees Fahrenheit to keep the concrete gaining strength.
Avoid the hottest part of the day and pour your concrete at night to give it the best chance to harden and cure before the sun rises. This will also help reduce the risk of concrete cracking and curing problems.
Aside from the temperature, you should also consider the time of day you pour your concrete. During summer, the temperature is often warmer and you may want to pour your concrete early in the morning or late at night to allow the mix to dry and cure before the heat of the day begins.
The temperature of the water you use in your concrete mixture also impacts the hydration process. Adding cold water to your mixture can cause more evaporation and increase the curing time. An industrial chiller will help you keep the water at a constant temperature and decrease your evaporation rates.
Humidity
The temperature and humidity of the air can have a big impact on how concrete sets, sets up and cures. The key is to know the effects of both of these factors, and to be able to adjust the process accordingly.
As a rule, warm weather tends to speed up the chemical reaction that occurs within an aggregate mixture when water is added to it. This can cause evaporation to occur at an increased rate, which can lead to problems with the setting and curing of the concrete.
In addition, the resulting moisture that is left behind can cause concrete to dry out faster than it should. This can result in what is called “plastic shrinkage cracking” if the concrete is not properly protected.
Humidity is a term that is often used by meteorologists to describe how muggy and humid the air is at a given time. There are two different ways to measure humidity: absolute humidity and relative humidity.
Absolute humidity measures the amount of water vapor that is present in the air at a particular temperature. Relative humidity, on the other hand, is a measurement of how much water vapor the air could hold at a different temperature.
When the relative humidity reaches 100%, it means that the air is saturated with water vapor. If the air cools a bit, such as when you get above ground or at higher altitudes, water vapor can condense into fog, clouds and other forms of liquid water that fall as rain or snow.
Relative humidity can be measured with devices such as hygrometers and thermometers, while absolute humidity is usually measured by readings of the dew point.
Most people understand that the humidity in the air affects how it feels outside. But most do not realize that it also affects how concrete works.
The relative humidity (RH) of the air is what matters most for how concrete will work, not the absolute humidity. This is because a high RH in the air can pull moisture from the concrete and release it into the air, while a low RH will push moisture out of the concrete and back into the air.
Moisture Content
When you are pouring concrete, moisture is one of the most important factors to consider. The amount of water in your concrete mix and the ratio of water to cement are the two main sources of moisture that impact the length of time it takes for your concrete to dry and become a solid structure.
The amount of water that evaporates from the surface of your concrete is also crucial. If the evaporation rate is too quick, your concrete can lose moisture quickly. This can damage the integrity of your finished product and cause it to warp and crack.
If the evaporation rate is too slow, your concrete may not fully cure, leaving it prone to stress fractures and weakening over time. This can be especially true if you pour concrete in a hot or humid environment and it is exposed to direct sunlight.
Luckily, there are several ways to measure the moisture content of a concrete slab. Some test methods measure the evaporation rates at the surface and others measure the relative humidity (RH) inside of the slab itself.
Anhydrous calcium chloride (CaCl) tests are a long-standing test method that uses a pre-weighed container of calcium chloride that is sealed over the top of the concrete floor. After 60 to 72 hours, the calcium chloride will absorb moisture from the concrete, giving the tester a reading of how much moisture is in the slab.
These readings are important because they help to determine how a concrete slab will react to having flooring installed on it. If the slab has too much moisture, wood and parquetry floors may warp and cup, carpets can grow mold and rot and low-permeability floor coverings such as vinyl or rubber can bubble and delaminate.
In fact, installing a floor covering too soon will make the slab even more susceptible to damage. As a result, it is crucial to get your concrete moisture testing done before you install any flooring on it.
Many contractors rely on surface-based methods for evaluating moisture and relative humidity levels in their concrete, including anhydrous calcium chloride testing, the hood method, and plastic sheet methods. These are often used along with in-situ relative humidity probes to ensure that they are taking the most accurate and thorough measurement possible.
Water Requirements
One of the most important variables when pouring concrete is the water-cement ratio. This is the ratio of water to cement weight in a batch of concrete, and it determines its strength.
The correct w/c ratio for a given application can vary depending on the type of concrete being poured. For example, for a commercial job, you may want to have a higher ratio than what is typical for residential work.
As with all things related to pouring concrete, precision is crucial when it comes to the amount of water added. Too little and the mix won’t moisten properly, too much and it won’t set or cure properly.
To avoid these problems, a number of techniques are used to increase the hydration rate and reduce set times and evaporation. For example, adding accelerants directly before or during the mixing process will speed up hydration and curing.
Keeping the temperature low when pouring also helps, as it reduces the evaporation rate. This is particularly important for hot weather. If the temperature rises too high, the concrete will evaporate too quickly and cause damage to the structure.
Another issue that can arise with pouring concrete in hot weather is the formation of capillary voids. This is a serious problem because it can lead to weakness in the concrete.
These voids can result in honeycombing of the concrete, and if you’re not careful, they can be as large as a few inches in diameter.
Therefore, it’s vital to have a well-thought-out plan before starting your project. Make sure you have the right tools and equipment for your area of work, and be prepared to cover the concrete as much as possible in order to keep it from drying out too quickly.
In addition, you should use a vapor barrier to prevent the moisture from entering your walls and ceilings. This will help to promote proper hydration and cure, and it will also protect the structural integrity of your building.
Lastly, if it begins to rain while you’re working, be sure to protect the ground with plastic sheets or waterproof covers. This will help to keep the concrete from getting damaged from the rain.
For the best results, always hire a reputable contractor like Yoder Laser Concrete!