In English | ISSUE 2/2023
Preface: Same speed limit on all roads?
The question I ask in the heading may appear strange in the editorial of Betoni-Concrete Magazine. However, a link can be found between speed limits and the use of low-carbon concrete for castin-place work.
Low-carbon concrete types are to a large extent based on the utilisation of furnace slag. Due to the significant amount of slag in the mixture, the strength development of particularly concrete with the smallest carbon footprint occurs at a slower rate to begin with than that of conventional concrete types. The slower rate of strength development is emphasised if also the temperature of the fresh concrete is lower than normal.
Low-carbon concrete is of interest to work sites, designers and developers alike. The BY Low Carbon Classification guideline published last year allows the desired low-carbon class to be indicated in the documents. The same low-carbon class cannot be defined for all the concrete types used in a building project.
To define the same low-carbon class for all the concrete works could be compared to defining the same maximum speed for all roads, both dirt roads and motorways.
In the speed limit analogy, the highways of lowcarbon concrete types are large-scale concrete structures in which very low-carbon concrete types can easily be used. By definition, the amount of concrete is large in these structures and thus they are of high significance when aiming at a low-carbon approach.
Small concreting jobs where fast and reliable strength development is essential are the dirt roads that require a careful driving style. These jobs include, for example, joint casting of load bearing prefabricated concrete units as well as various structural concreting jobs, such as consoles and correspond structural components subject to heavy loads. These often require quite a small amount of concrete. Conventional concrete types can be selected for these jobs without any concerns of increasing the total carbon foot print of the project.
Jussi Mattila, Managing Director, Association of Concrete Industry in Finland