RE-CON AGG 90: an admixture for challenging aggregates in cold climates

I have a Master Science in Chemical Engineering and Biotechnology and a bachelor’s degree in economics. I started working at Mapei AS after I finished my studies as a Sustainability and Technology Trainee in January 2023. After the trainee-period, I started working as a R&D Engineer for Liquid Admixtures and I currently work on admixtures and solutions for a more sustainable concrete production.

RE-CON AGG 100 is a water absorption inhibitor developed for challenging aggregates by Mapei SpA R&D Centre in Milan, Italy. RE-CON AGG 90 is a new, “Nordic” version of RE-CON AGG 100, which we developed at Mapei AS Research & Development laboratories in Nord-Odal, Norway. In the new formulation, the retarder has been removed to make it more suitable for the cold Nordic climate. When adapting the RE-CON AGG 100 formulation to develop RE-CON AGG90, we started by testing the new admixture in mortars. Then we tested it in concrete mixes, first with our standard aggregates. The results showed that RE-CON AGG 90 did not contribute to any loss of compressive strength, either early or late. It also had a positive effect on the initial workability and the open time. Further on, we tested RE-CON AGG 90 in concrete mixes where parts of the aggregates had been replaced with recycled concrete aggregates, as part of the MILBET-project.

We definitely see an increased interest in the industry to make concrete more sustainable. Sustainability is a major focus within research and development. The interest for our RE-CON Line and MAPECUBE products are increasing, which indicates that the market is really interested in more sustainable solutions. To take Norway as an example, the Norwegian authorities have recently introduced stricter waste management regulations and the Norwegian Concrete Association published a low-carbon standard in 2015, which was last revised in 2024. We are still awaiting an increase in demand for low carbon concrete for general use in the residential sector. So far, the demand is driven by high profile projects. To increase the use of more sustainable solutions, such as low-carbon concrete or recycled aggregates, I think they need to be more financially advantageous and/or required by the authorities.

Mapei AS participates in and contributes to several research projects with a focus on sustainability in cooperation with partners from the Norwegian concrete industry. One of these is the MILBET project. MILBET stands for "Miljøvennlige betongløsninger" or "Environmentally friendly concrete solutions". The project owner is Nordland Betong, a Norwegian concrete producer based in Bodø in the north of Norway. In addition to Mapei, the other partners are Nordasfalt, Østbø and Cemonite, with Heidelberg Materials, the University of Tromsø and the Norwegian Concrete Innovation Cluster as supporting partners. The project started in 2024 and will continue for another two years. One of the main objectives of the project is to produce concrete with more recycled materials, mainly by replacing part of the natural aggregates with recycled crushed concrete aggregates (RCA). Initial tests in the Mapei AS Research & Development Laboratories showed that replacing part of the natural aggregates with RCA resulted in a significant reduction in workability due to the porosity of the RCA. To solve this problem, we tested RE-CON AGG 90. So far, we have produced concretes with 50% substitution of both 0/8 mm and 8/22 mm aggregates. This is a higher substitution rate than the current Norwegian standard allows. The concrete mix with 50% of the natural aggregates replaced with RCA showed a difficult workability compared to the reference concrete with 100% natural aggregates. By introducing RE-CON AGG 90 into the mix design with 50% RCA, we were able to achieve the same initial workability and even longer open time than the reference concrete with 100% natural aggregates. These were very positive results! One observation in our testing has been occasional increase in air content, with a negative effect on the compressive strength. This is a normal phenomenon that occurs with some crushed recycled aggregates and cannot be attributed to the RE-CON AGG admixture as such. Our R&D laboratories are continuing to investigate these issues, and recent tests have been promising in resolving this problem. Another goal in this project is to create a low carbon concrete mix design with significant reduced CO₂ emissions. Our next goal is to conduct testing with MAPECUBE admixtures to compensate for the loss in compressive strength caused by lower clinker content. With our new retarder-free formulation, precast concrete producers who are using recycled aggregates can now use RE-CON AGG technology without extending the setting or hardening of the concrete. We look forward to future tests and hopefully positive results!