Mobile laboratory for measuring early age properties of concrete

Major construction projects such as the Great Belt link, the Øresund link and the Malmø Citytunnel pose great demands on the concrete durability. Significant expenses can be avoided by carrying out an optimization of the casting and curing process.

An in-depth optimization of the casting process may be carried out based on temperature–stress calculations on the structure. Such calculations require detailed knowledge of the early age properties of the concrete, e.g. the creep and shrinkage properties.

Monitoring the early age creep and shrinkage behavior is a complicated test comprising measurement of de-formations of a few microns and strict control of the temperature regime and it can only be executed in a controlled laboratory environment.

Many modern high performance concretes have a short setting time and thus, do not leave time for transporting the fresh concrete to a laboratory for casting of test samples. Furthermore, as the measurements have to start as early as 12 maturity hours after casting, the samples cannot be transported without being damaged.

Consequently, the determination of the early age concrete properties often requires these to be measured on-site.

The Mobile Laboratory
To solve this problem, the Concrete Centre at the Danish Technological Institute has developed a new concept; a mobile laboratory for measuring the hardening properties of concrete on-site.
The largest challenge is to ensure constant temperature in the room where the measurements take place, independent of the outdoor temperature and the heat developed by the technical equipment used in the test set-up.

The mobile test set-up is integrated in an insulated container separated in two parts; one part for the test set-up and one part for the hydraulics and the cooling/heating system.

How can Danish Technological Institute help you?

• Determination of the early-age creep and shrinkage of concrete on-site using the Mobile Laboratory.
• Determination of early-age concrete properties in the laboratory of the Danish Technological Institute. Strength development, heat of hydration, early-age creep and shrinkage, etc.

Cases
The Concrete Centre has applied the Mobile Laboratory for testing hardening properties on-site at the Malmø Citytunnel (2005 – 2007). For this project, the mobile laboratory was been applied successfully for testing of 10 concretes at outdoor temperature ranging from plus 30 °C to minus 10 °C. Through all test periods, the mobile laboratory fulfilled the strict requirements to temperature control and measuring accuracy.