As the temperature drops, pouring concrete can become difficult, and you have to take extra precautions to avoid problems such as slow setting, strength issues, early-age freezing, and others. You should begin by choosing the right ready mix concrete delivery for the project, then follow these tips.

Monitor The Temperature And Its Effect On Concrete

The ideal temperature for pouring and setting concrete is 50°F to 75°F. You can’t always get this range, so you need to monitor the temperature so you can adjust things. If the temperature is below 40°F, concrete will set slowly as the coldness will start slowing down the hydration process. And at temperatures of 25°F, the water content in concrete may freeze before curing, which creates durability problems.

Use Cold-Weather Concrete Mix

When you see that the weather at the site will be below 40°F, you should use a cold-weather concrete mix. As you’re ordering ready-mix concrete, mention this in your requirements. This means the manufacturer should perform one or more of these things:

Add accelerators: They are chemical admixtures that increase the rate of hydration in concrete. This speeds up the setting time and triggers curing more quickly, which is required for cold-weather concreting.

Use warm mix water: Room temperature water (cold in winter) can freeze during the mixing and pouring stage, creating a lot of problems. This is why warm mix water is used to keep the temperature of concrete warm enough so that it’s workable.

Use a lower water-cement ratio: Water in concrete can freeze and expand, leading to flaking and cracking. This is why manufacturers use a lower water-cement ratio, so there is less water to freeze and expand. And the concrete is still fluid enough that you can work with it.

Reduce or avoid using fly ash in concrete: The process of pulverized coal combustion creates a powdery residue called fly ash. It’s used in concrete as a sustainable way to reduce water demand in mixing and increase the setting time. But in winter, you don’t want to increase setting time, so reducing the amount of fly ash or avoiding it altogether is suggested.

Add air-entraining admixture: An air-entraining admixture introduces microscopic air bubbles in the concrete mix. This creates space for water to expand without cracking concrete. However, its usage should be carefully controlled. It should not be used in excess unnecessarily as it reduces the compressive strength of concrete.

These requirements apply to both commercial projects and residential projects like building a pool or a driveway.

Choose A Concrete Supplier Carefully

You should pick a concrete supplier Montgomery County who prepares concrete following the exact requirements of their clients. Moreover, they should have insulated truck drums for winter or the drum should be wrapped in an insulated jacket or be equipped with temperature control.

Moreover, heat loss still occurs during transit, so they should calculate how much heat loss will occur and adjust the concrete mix accordingly. In most cases, when the truck leaves the plant, the temperature of the concrete mix should be around 60°F-70°F. There can be a 5-15°F loss during transit.

Prepare The Site

Site preparation is important because you don’t want to pour concrete on a surface that would instantly or quickly freeze it. Even if freezing is not a concern, cold temperatures slow down the setting and curing rate, so you need to prepare the site accordingly.

Frost Cleanup

It’s a standard procedure in cold-weather concreting to remove all snow and frost from the site, forms, reinforcements, and anything you will use during the process. You should also use any heating methods to thaw the sub-base. We have mentioned heat enclosures below.

Plus, never pour concrete without first checking the sub-grade temperature. Moreover, the ready-mix concrete temperature before pouring should be 50°F. The lower limit is 40°F. It must not be lower than that.

Windbreaks

To control the temperature of the site, you can set up barriers called windbreaks. They keep the freshly poured concrete from being exposed to the chilly wind. This is done to prevent wind erosion and wind chilling. Wind erosion can cause an uneven finish, while wind chilling leads to premature drying or freezing of concrete.

Heat Enclosures

Heat enclosures are temporary spaces or coverings for the site where you want to pour concrete to keep the cold weather from freezing it or keep the temperature above 40°F.

With these enclosures, you can not only control temperature but also humidity. This doesn’t happen directly because, apart from the cold air, the heater can cause lower humidity levels as well. However, you can use steaming, fogging, or wet burlap to manage the moisture levels of the freshly poured concrete surface.

Insulated Blankets

Insulated blankets are made of woven polyethylene (HDPE or PE) or PVC and the central layer is insulated foam. Once placed on concrete, they protect it from freezing and quick heat loss, and ensure proper concrete setting and curing.

However, you need to be careful not to lay the insulated blankets too early when the concrete hasn’t set, as this will leave marks and depressions on the surface. To avoid these problems, wait for the concrete to achieve its initial set.

But placing insulated blankets is not of help if the temperature is below 40°F and you need to protect the concrete before the initial set.

Because of this, you can employ insulated blankets as temporary curtain walls and for heat enclosures. You don’t need to wait for concrete to reach its initial set for this method. You can use them with a support like temporary wooden structures, forms, or something else.

Heaters

You can use various types of heaters depending on the project and requirements to warm the space, such as hydronic heaters, indirect-fired heaters, electric heated blankets, etc. If you’re not setting up an enclosure, use hydronic heaters.

Cold Weather Safety

Apart from protecting the concrete and the equipment, there should be proper safety measures at the job site to keep workers safe. There should be proper cleanup before beginning work, so there is no ice or frost on the job site as frost can be a slip hazard. Moreover, all the equipment, especially for heating, should be carefully employed to avoid accidents and mishaps.

For instance, when you consider heaters, choose indirect-fire heaters as the flame is contained inside the chamber and they have a flue that makes ventilation easier. Moreover, direct-fired heaters release carbon dioxide, which is damaging to concrete, while indirect-fired heaters don’t release it. They do release carbon monoxide through the exhaust, so keeping the exhaust away from indoors and the air intake is critical for safety. Plus, placing them in non-combustible surroundings is paramount to avoid a fire.

Finishing

You should wait for the bleed water to evaporate before finishing. As you’re working in cold temperatures below 40°F, the bleeding will be slower, so prepare to wait more than usual. Moreover, avoid watering the concrete as it may freeze and cause problems.

Post Curing

You should not remove the heating arrangement, such as insulated blankets, before the concrete reaches an early compressive strength of 500 psi (3.4–3.5 MPa). And when removing blankets, perform the process slowly to avoid thermal shock and damage.

Conclusion

Pouring, setting, and curing concrete in winter is done a bit differently than usual. So, remember these tips and pick a reputable ready mix concrete supplier Rockville who manufactures high-quality concrete following your project’s requirements.