Looking for innovative and environmentally responsible applications

By Charlotte Heesbeen, Technical University of Delft

SeRaMCo will showcase the use of secondary aggregate in concrete and the fact that it does not have to be as complicated as sometimes assumed. During the MAKING workshops at TU Delft, the great architectural potential of CDW (Construction and Demolition Waste) in precast concrete is an ongoing topic of investigation. Students look for the added value of CDW in concrete ranging from béton brut, exposed concrete and rammed recycled aggregate, by making objects with added properties. Though the visual component of the materials we use in architecture is unarguably a factor of great importance, functionality must be addressed at the same time.

Experimental models made by students during the MAKING Workshop

The benefits of precast concrete are manifold, including the freedom of shape and a controlled quality and high installation speed, that in situ concrete in many cases cannot offer. On the other hand, concrete is, undeniably, a building material that contributes significantly to resource use, waste production and CO2 emission. Thus, we need to take responsibility for the damaging impact that the production and use has caused in the past and will cause in the future. Our common task and moral obligation should transcend merely recycling materials. This implies that our precast products need to repair the intrinsic damage they cause on both the earth’s resources and her inhabitants, during their production, their lifetime and at end of its life-span. In other words, building elements could contribute positively to environmental issues we face globally, complementary to what they are made for in the first place. To repair the aforementioned environmental damage concrete building elements cause, is an ambitious design task. But it is one we feel responsible for at TU Delft in SeRaMCo, when we propose new precast concrete products.

TU Delft is looking beyond the traditional applications of precast concrete. Applications that offer more value than ordinary building components and, indeed, contribute to repair the damage their production costs in the first place.

Recently, we have started to identify the acoustic properties of recycled aggregates in comparison to concrete out of primary raw materials. In theory, size and material have an impact on the acoustic performance of recycled aggregates. We have tested samples in an impedance tube have tried to show this. So far, we have seen, that the use of recycled aggregates bound in concrete, does not perform different than concrete with natural aggregates, river gravel in this case. Presumably, this is directly related to the way mortar encapsulates both natural and recycled aggregates, which rules out any effects of the recycled aggregates. We have experienced a better result using recycled aggregates in porous concrete compared to massive concrete with natural aggregates, although the recycled aggregate is probably not decisive in this comparison. The use of unbound recycled aggregates, on the other hand seems promising, and is up for testing soon. If we can prove a better acoustic absorbance of secondary aggregates, this will open up possibilities for prefabricated elements, such as sound barriers in high traffic urban contexts.


Graphical representation of the measured acoustic absorption of concrete with natural aggregate (blue line) and porous concrete with recycled aggregate (green line).

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