In an ever-more polluted and growing world, recycling has become a need to properly develop under high environmental consequences. The economic systems which endured since the Industrial Revolution can be no more and our high consumption matched with industry’s scheduled obsolescence means we stand now at a critical point in mankind’s existence. Producing less and slower actually means more now.

To act in such a moment, the building industry must understand how to recycle and reutilize its main materials. And no material is more pivotal than Concrete to our twenty-first-century society. While understanding alternative options that represent more green and viable materials are important, the reality is that, right now, our world is covered in concrete – and action must be taken today. So, what is Concrete Recycling, and how does it affect our architectural practice?

As we build newer structures, old ones are demolished, and that’s where concrete recycling comes into play. The rubble, which traditionally would go to landfills, now goes to a crushing machine in loco (at the demolition site) which crushes it to a point of manageable chunk sizes. Of course, there are some problems when it comes to different versions of concrete other than the traditional one with Portland cement. For example, this machine isn’t developed to crush and properly manage wood, glass, trash or paper, which can be seen in green alternatives to everyday concrete. Although that’s a considerable problem, metal doesn’t stop the process, since it can be picked up manually or with magnets, or even be melted and re utilized in other situations, which is great since most concrete buildings today have rebar. It’s also important to mention that materials such as Aircrete contour that problem since its air bubbles are not impeditive to the crushing machine. For the future, developing machines fitted to the green alternatives of this building block is an interesting invention that could solve many problems in order to achieve a truly green building industry.

Nonetheless, once crushed, what´s the use of said rubble? It is commonly cleaned up and verified in a second phase, to be later used as gravel or a sub-base aggregate to asphalt paving or permeable walkways, but there are other uses which can be important to architects. A personal favorite, for example, is the incorporation of this rubble in gabion walls, which can be used as an integral part of an architectural project. Rip Raps are also interesting in seismically active countries. Other creative adaptations are studying its application in landscaping mulch (i.g. replacing river rock) and even in recreating oceanic reef habitats. Above all for everyday appliances, old concrete can become brand new concrete if it’s uncontaminated: the rubble can be the dry aggregate of newer versions of concrete, making its production process a lot more eco friendly. While there are studies running on the durability of this reutilized material, other aggregates such as fly ash can strengthen it to a satisfactory state.

But there are still questions standing about recycling concrete, such as the benefits of using it. The obvious one is saving landfills space and, with that, also lowering transportation costs since the crushing machine can be used in the demolition site. More than that, it creates employment opportunities for the companies responsible for the said process and severely reduces the costs of producing new concrete, especially when it comes to water and CO2 expenses and waste related to producing, burning, transporting and disposing of the traditional concrete and cement aggregates. This means that the production costs of concrete or gravel mining – be them financial, social or environmental- are far bigger than just reutilizing old rubble to make new concrete or gravel.

For architects, all this means a shift in our creative process. Since the modernist movement, concrete has become an untouchable entity, and that’s one reason concrete recycling hasn’t expanded yet. Other reasons are the relative lack of studies in integrity, quality standards and security -which are mostly being conducted at this moment and therefore cannot be applied by governmental and technical institutes- and most importantly, the pressure of traditional concrete companies that don’t want to lose their market share. To change this, architects must apply this new technique and structure in projects so that they become benchmarks and examples to others, but mostly to break the common connection today between the building and the concrete dependency that was developed in the modernist movement. This is a status quo with high market interest. It’s important to know the Twenty-first century isn’t modern anymore; it is contemporary, it has its own voice, and that voice is pro-green building.


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