How Cold is Too Cold to Pour Concrete?

What Temperature is Too Cold to Pour Concrete?

Experts agree that the best temperature to pour concrete is between 50-60 °F. The necessary chemical reactions that set and strengthen concrete slow significantly below 50 °F and are almost non-existent below 40 °F. Even when daytime temperatures are within the satisfactory range, winter concrete setting creates risks that could result in weak, inadequate concrete. If nighttime temperatures are below freezing, the water in the concrete will freeze and expand, causing cracks. Additionally, if temperatures reach below 40 °F (but not freezing) during set time, concrete will take much longer to reach required strength. However, if the correct measures are taken, concrete can still be successfully placed during even the coldest months of the year.

Things to Consider with Cold Weather Concreting

Before embarking on a cold weather concrete project, it’s important to determine any special strength requirements or considerations. This will help as you schedule your pouring and determine which strategies you will use to keep your surroundings and materials warm. The predominant challenge you will face during a winter concrete project is ensuring that the concrete sets before it is exposed to freezing temperatures. You might take the following suggestions into consideration as you plan your upcoming project:

  • Use heaters to thaw frozen ground, snow or ice.
  • Use hot water to mix cement.
  • Keep dry materials in a dry, warm location.
  • Use products designed to set quickly. During cold weather, these products will not set as quickly as the instructions may indicate, but will set faster than conventional materials.
  • Use additives that accelerate set time. Use caution; if additives contain calcium chloride, any rebar or metal wire mesh in concrete will rust and cause concrete to crack.
  • Use extra cement (typically 100 lb/ cubic yard) to make the reaction hotter and cause concrete to hydrate more rapidly.
  • Remember that you still need to wait for bleed water to evaporate. Incorporating the water into the surface during finishing will weaken the surface. Bleeding starts later and takes longer during cold weather; you can use squeegees or a vacuum to remove water quickly.
  • Wait until concrete has reached desired strength to remove any framework. If the framework is removed too early, the concrete will be damaged and the surface could collapse.

Maintaining Ideal Temperature

After implementing the above suggestions, It’s important to consider how you will keep concrete at the correct temperature during the curing process. Concrete must maintain a temperature above 50 °F for approximately 48 hours for the correct chemical reactions to take place. Two popular options used during cold weather concrete curing are heated enclosures and insulated blankets. If using an enclosure, ensure that the structure is both wind and waterproof. Additionally, ensure that there is proper ventilation for the space heater. Heaters cause an increase in carbon dioxide that could cause carbonation in the surface of the concrete.

Powerblanket Concrete Blankets

Powerblanket® concrete blankets are an extremely effective option for attaining and maintaining the correct temperatures for concrete pouring and setting. Powerblanket® concrete blankets can be used to thaw ground before pouring concrete and again after finishing to keep concrete from freezing. Utilizing Powerblanket® concrete blankets will ensure that concrete is kept at the correct temperature for the necessary reactions to happen quickly and the desired strength to be reached.

Increase Gas Flow Rate Solutions for You

Increase Gas Flow Rate

“How do I increase my gas flow rate?”  Search this question online, and you may get some of the answers below:

Pressure of the gas in a container is created by the number of collisions the molecules have with each other and with the surface of the container. Increasing the number of collisions will increase gas flow rate.

There are a few ways to increase the number of collisions.

  1. Add more molecules. More molecules in the same size container will increase the number of times molecules collide.
  2. Increase the temperature. Increasing the temperature will increase the speed at which the molecules move and therefore increase the number of collisions that take place in the container.
  3. Decrease the size of the container.  This forces the molecules into a smaller area, increasing the number of collisions that take place.

Assessing the Situation

Let’s assume that you already have the tank you want to use, and you are not interested in making any changes to the container/system.  Option 3 is out because it deals with changing the size of the container.  Let’s also say, to your knowledge, the tank is full and there are no more molecules to add, eliminating option 1 as a viable solution.  That brings us to temperature.

When the temperature is lower, it is very difficult to maintain an optimal gas flow rate.  Lower temperatures=fewer collisions in the tank.  This prevents the gas from vaporizing, rendering it virtually useless.  Propane, butane, nitrogen, oxygen and other compressed gasses need temperature control to ensure optimal gas flow rates.  Bringing the container/system up to a temperature above the cooler existing ambient temperature will result in increased pressure, flow and efficiency.

Heating Blankets to Increase Gas Flow Rate

Heating blankets are an excellent solution to increase temperatures for improved flow rates.  These blankets/jackets wrap around or lay over a variety of products and equipment to provide heat.  If installed properly, these apply heat directly to the medium, eliminating heat loss from exposed surfaces.  Heating blankets are easy to install and remove from the equipment requiring service.  They offer integral temperature control and heat larger areas with a lower temperature gradient.

Powerblanket® offers a variety of gas cylinder heating blankets for controlling temperatures of compressed gasses.  These heating blankets provide uniform heat for controlling temperatures of compressed gasses and a uniform barrier of heat across the entire cylinder.  This superior heating solution reduces cost by optimizing container temperatures and increasing gas flow rates.

Case in Point

A large semiconductor manufacturing company needed a new product to improve their semiconductor manufacturing process. They needed to maintain the flow of their gas delivery system more precisely, and their existing solution did not offer the consistency they desired.

Powerblanket designed a heating product for their gas delivery system that maintained the precise temperature and gas flow rate for hydrocarbon gases.

The company’s management team later admitted that they were initially against the idea of switching to the Powerblanket specialty gas heating solution. They said, “We didn’t think it would work because it was half the power of the status quo product, but after we gave it a try, we were immediately sold.  It’s a fantastic product and the sales and engineering support we received was excellent”

Another Example

Shannon Stillman, a Pyro Engineer at Thor Productions, said, “We use propane in large volumes – over ½ ton each night per event. Each of our cylinders are wrapped with a Powerblanket® Gas Cylinder Heater, extending the allowable duration by at least 60%. This equates to hundreds of usable lbs. of propane per night. In addition, the UL listing and safety ratings of the Powerblanket products resolve the concerns of the site safety managers, AHJ’s (Authorities Having Jurisdiction) and Fire Marshals.”

The Powerblanket Advantage

Powerblanket has the best gas cylinder heaters on the market. Our heating blankets will overcome the effects of cold weather and maintain pressure and efficiency on any gas cylinder.

  • Increase gas flow rate and efficiency of gas cylinders
  • Save money by optimizing gas and material usage
  • Eliminate unnecessary cylinder refills in cold weather
  • Insulated full-wrap design

Winter Road Maintenance and Winter Road Construction

Winter Road Maintenance

Winter Road ConstructionWinter Road Maintenance

Typically, it is unwise to do any major structural winter road maintenance in the cold winter months.  Many professional paving companies joke that the best time to do winter repairs is in the summer.  Winter road construction is not so much dictated by the season, but rather by the temperature.  Warmer states have much longer active road construction periods than states with cold winters.  Without special engineering permission, most states prohibit paving in conditions below 45-50°F (for example asphalt conditions must be 50° and rising in Utah).  Never install asphalt or concrete on a frozen subbase; this will only ensure additional work for you when the conditions improve and you have to redo the job.  

 

Emergency Pothole Repair

For temporary repairs such as potholes use cold mix asphalt.  If the temperature is below the recommended level and it is an emergency, cold mix asphalt will work.  During this cold weather repair, remove all ice, moisture, and debris from the affected area using a heat source.  Keep in mind, this repair is meant to be temporary and should be permanently remedied when conditions improve

 

Winter Road Repairs: Crack Sealing

Crack sealing is actually preferred in colder months because pavements expand and contract with seasonal temperature changes. Consequently, cracks and joints are expanding and contracting when the pavements move. Crack sealing is a preventative winter road maintenance practice meant to extend the life of pavement. Since cracks on the pavement surface allow water and incompressible materials such as sand, dirt, and other debris to enter the pavement structure, these cracks can dramatically accelerate deterioration and weakening. Sealing cracks prevents further deterioration of the pavement and, when properly executed, can extend the life of the pavement anywhere from 6 months to 4 years. 

 

 

Crack Sealing Tips

  1. As recommended with the pothole repair, clear the crack of moisture, dirt, debris, vegetation and chemical deicers to make the sealing more effective, use a heat lance and/or compressed air.  If using a heat lance take care not to burn or scorch the pavement and the place the sealant before the pavement in the crack cools to allow for the best adherence of the crack fill materials.
  2. Seal all cracks from 1⁄4 inch to 1 inch in width the entire length of the crack. Cracks smaller than 1⁄4” will not retain sufficient sealer to flex in the cold. Cracks greater than 1” will sag and possibly prematurely fail without the installation of HMA or backer rod.
  3. When repairing cracks, fill the entire crack and level any affected area to ensure a smooth and level pavement surface.
  4. Apply the sealant or repair material only when the sealant or repair material is within the manufacturer’s recommended application temperature. Special care must be taken to assure that the sealant temperature does not exceed the manufacturer’s recommendations; otherwise the polymers may be destroyed therefore reducing the sealant performance.
  5. Keep in mind that more sealant is not always better. Over applying sealant material can lead to problems when paving over with HMA or bleeding up through the seal or paving application.
  6. New sealants are not designed to be “road glue”. They are very sticky and have tremendous bonding power; however, they were not made to “hold the road together”. Crack sealing has one objective: to prevent water from further damaging roads. Sealing “buys time” and saves money by delaying the expense of major reconstructive pavement work.

 

Powerblanket can help with Winter Road Maintenance

Whether you need a means for protecting temperature-sensitive materials in storage, or you need a heating solution for onsite temperature maintenance, the Powerblanket Hot Box will do the job.  This versatile heating solution accommodates remote-location use, job site heating, the transporting of temperature sensitive materials.  The revolutionary design of Powerblanket Hot Boxes provides uniform heat to all materials stored inside. This reduces the chance of having any hot and cold spots. If stored properly; chemicals, industrial products, and temperature sensitive materials will last longer and be more effective.

Winter road maintenance