Ready-mix concrete is fully mixed and prepared for use before being delivered to a work site. This concrete is typically preferred over on-site concrete because the mixture is more precise, more convenient, and reduces work site confusion. During the winter months, cold weather can affect ready-mix projects, and if the concrete provider is not prepared for them, they can become problems.
””Outdoor temperatures between 50 and 75 degrees Fahrenheit are ideal for pouring ready-mix concrete foundations. Very cold weather on the other hand, can make concrete jobs much more difficult and sometimes impossible to complete without compromising the quality of the work. Despite this, many of the problems associated with concrete work during cold weather can be overcome if the concrete provider is well aware of them.
- Slow Curing Time
When temperatures drop below 50 degrees, concrete sets very slowly. Below 40 degrees, hydration reaction basically stops, and the concrete doesn’t gain strength. Adding an accelerated admixture to modify the properties of the concrete mix will speed up the curing time. Water is used to create the concrete mixture. When all of the water that is used for the mix freezes, it expands, causing the concrete to crack. The key is doing what you can to make sure the concrete sets fast enough to prevent this, which is what an accelerator does. Also, switching to a special sealer that uses a faster solvent might help avoid problems and ensure that the surface sets properly.
- Decreased Flexibility During Casting
Casting concrete in very low temperatures requires certain precautions to be taken. Some suppliers of ready-mixed concrete are able to supply heated concrete, which can be delivered to the work site at temperatures above 50 degrees even in the coldest weather. Concrete pros add hot water to the mix to keep the concrete workable. Concrete should be covered with insulating material once cast, and the heat of hydration will help to maintain the temperature of the concrete after the setting process starts. Most producers will try to have the concrete be at least 65°F when it leaves the plant, which is generally good enough depending on air temperature and thickness of the concrete element.
- Pouring Ready-Mix Concrete on Frozen Ground, Snow or Ice
Frozen ground must settle after it thaws from the cold. This settling can crack the concrete if it was poured while the ground was frozen. Not only that, but crusting can occur when working with cold foundations—causing the top part of the concrete to set, but the concrete in contact with the ground to set more slowly and remain soft. Because of these issues, it is never recommended to pour concrete on frozen ground.
- Carbonation of Concrete
A building heated by temporary heaters without ventilation or with poor ventilation, including gas-powered equipment, can cause carbon dioxide levels in the air to rise. When the carbon dioxide from the air reacts with the calcium hydroxide in concrete to form calcium carbonate, the process of carbonation takes place and is essentially the reversal of calcination of lime. Carbonation leaves the concrete with a chalky carbonated surface and a center that is too soft to last. An easy way to avoid issues of carbonation is to use heaters that can vent their exhaust to the outside of the building.
Talk to Concrete Professionals
Ready-mix concrete doesn’t like the cold—but it is still possible to successfully complete your concrete project if proper preparations for the elements are made. With over 18 plants around the state, the professionals at Razorback Concrete are well prepared for the Arkansas winter months. They can answer any of your cold weather concrete questions and help make sure your project is completed successfully. For a free ready-mix concrete quote, contact a ready-mix concrete expert today.