Towards a Swedish “green” concrete: Partial substitution of cement with local clays

Important results from the project

While concrete is necessary to face the global infrastructure needs, its production has an inevitable CO2 environmental footprint: about 6% of the total anthropogenic CO2 emissions. The best way to reduce this is to decrease the amount of cement used, which can be done by replacing a part of the cement with supplementary cementitious materials. Swedish clays already show promising results, but we need to investigate and optimise binders made with Swedish clays to obtain the best possible performances. This will lead us to the path toward a sustainable concrete industry.

Expected long term effects

We studied the hydration of various mixes to optimize their design. For binary binder, a maximum of 30% of clays (+70% cement) can be used. For ternary binder, mixes with 20% clay + 10% limestone and 30% clay + 15% limestone gave good results. The sulphate content was adjusted with 1% of gypsum to optimise the hydration. The strength development of those mixes is below expectation, due to the low fluidity and thus a hight porosity. This is fixed with addition of superplasticiser. This project led to the funding of a new project by the industry to study the interactions between admixture and clay.

Approach and implementation

The results of the project were communicated to industrials partners. Even though the strength of the samples were below expectations, the results were promising enough to convince the industry to go further with a new project. In addition, the study of the activation also reveals that there is a need to develop the mechanical activation by grinding at an industrial scale. The project is thus successful, and the results highlight various path to continue the development of sustainable concrete containing clays.