The Theory of Maturity

Tracking changes in concrete temperature is the first step in estimating the strength and quality of the finished product.

Importance of Concrete Temperature
Concrete temperature is directly related to the development of strength. Fresh concrete can be damaged when exposed to very low or very high temperatures. Many agencies have specifications that regulate the fresh concrete temperature upon delivery, as well as maximum and minimum temperatures during critical early ages. Using the COMMAND Center, you can make all these measurements (fresh, max, min) using one system.

Temperature Gradients in Mass Concrete
When a large amount of concrete is placed (such as in a large footing, dam, or pavement) the thermodynamics of the curing process as well as the geometry of the section can cause temperature gradients (uneven temperature distributions) to occur in different places in the concrete. A large enough gradient can cause cracking and reduce the durability and life of the concrete structure.

Gradient temperatures are often measured as an absolute temperature difference between two or more points in the structure. The COMMAND Center improves on this by reporting the temperature gradient between two sensors. Unlike other maturity systems where different sensors are required for measuring temperature gradients, our sensors can measure both maturity and gradients.

Curing Temperatures Affect Final Strength
An effect known as “crossover” relates the long-term strength of concrete to the temperature during the curing period. As the graphs below show, the same mix will gain strength quicker at high curing temperatures, but at later ages the strength curves will “crossover” leaving the concrete cured at the highest temperature with the lowest final strength. This is important because most design strength criteria assume concrete to gain in strength after the standard 28 days.

The varying temperatures concrete pavement is exposed to throughout the year have been correlated to many overall performance issues, especially freeze-thaw resistance. Since the sensors used by the COMMAND Center will operate for up to 10 years, researchers currently use them to monitor seasonal pavement temperatures and urban heat island effects.