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Sustainable concrete: Design and testing

J.H.M. Visser1, S. Couto2, A. Gupta3, I. Larraza Alvarez4, V. Chozas Ligero4, T. Sotto Mayor2, 5, R. Vinai6, P. Pipilikaki1, A. Largo7, A. Attanasio7, Chaolung Huang8, M. Soutsos6

1 TNO, the Netherlands
2 CeNTI, Portugal
3 BASF, Germany
4 Acciona, Spain
5 EMPA, Switzerland
6 Queen’s University of Belfast, United Kingdom
7 CETMA, Italy
8 TBTC, Taiwan

Producing concrete with secondary raw materials is an excellent way to contribute to a more sustainable world, provided that this concrete has at least the same performance during its service life as concrete made with the primary raw materials it replaces. Secondary raw materials for Light Weight (LW) aggregates (rigid polyurethane foams, shredded tire rubber and mixed plastic scraps) have been combined with secondary raw materials for the binder (fly ash, slag and perlite tailings) making sustainable concretes that were investigated for their suitability as LW, highly insulating concrete for four different types of applications.

Compliance to desired engineering properties (workability, setting time) was not always feasible: it was mostly the low workability of the mixtures that limited their application. Contrary to well established cements, steering the workability by adding water was not an option for these binders that rely on alkali-activation. Eight successful mixtures have been tested further. The results have shown that it is possible to produce a non-structural sustainable concrete with good mechanical and thermal insulation properties.

Design of concrete made with novel materials is currently not feasible without extensive experimentation as no design rules exist other than empirically derived rules based on traditional materials. As a radical different approach, a flexible concrete mix design has been developed with which the concrete can be modelled in the fresh and hardened state. The numerical concrete mix design method proves a promising tool in designing concrete for performance demands such as elasticity parameters and thermal conductivity.

Key words: Sustainable binder, sustainable aggregate, workability, mechanical properties, thermal conductivity, numerical concrete design, performance