SANDBAG CASTLE — The future of concrete is now

Artist Yvonne Mak translates this question into a concrete sandbag castle, bringing together a range of low-carbon materials. The future of concrete is now.

Contradiction

What if the material we rely on to protect us from climate change is simultaneously contributing to it?

Sandbag Castle makes this contradiction visible. Hundreds of seemingly ordinary sandbags are stacked into a castle surrounded by water. A sandbag is one of the first lines of defence against rising water; a castle is a centuries-old symbol of protection. Yet all of these sandbags are actually cast in concrete.

Concrete is essential to the infrastructure that supports and protects modern life: from homes, bridges and energy infrastructure to flood defences. At the same time, the production of conventional cement and concrete generates significant CO₂ emissions. Sea levels are rising and extreme weather is making protection against water increasingly urgent. As a result, we depend on a material whose production contributes to the climate change we are trying to protect ourselves against.

Sandbag Castle does not suggest simply stopping the use of concrete. It asks: what kind of concrete do we choose to build our future with?

The Future Is Now

The good news is that we do not have to wait for a solution. Lower-carbon concrete and cement technologies already exist. Sandbag Castle brings together more than ten approaches, each addressing the environmental impact of concrete from a different angle.

These include calcined clay; SCMs & blends (Q-Cem, BlueCalc, GROENR, ACT); geopolymer concrete (RAMAC, INVIE); recycled or dredged materials (BlueFiller, BlueCalc, Washed Concrete Sand & Recycled Concrete Aggregate from old concrete, Renewi’s FORZ); CO₂ utilisation (Paebbl Rebond 300, Clim@Add); lightweight reinforcement or aggregates (MasterFiber, LECA M); supporting admixtures (MasterCO2re); and self-healing concrete (Penetron Admix, Basilisk Healing Agent).

Together, these approaches show that the possibilities for producing concrete differently already exist. Yet they are not yet a standard part of the way we build. Sandbag Castle therefore asks not only what is technically possible, but also why we are still waiting. The future of concrete is not just something to work towards. It has already begun.

not yet a standard part of the way we build. Sandbag Castle therefore asks not only what is technically possible, but also why we are still waiting. The future of concrete is not just something to work towards. It has already begun.

Another Perspective

Mak’s work often starts with an object, material or form that initially appears ordinary or innocent. By shifting it just enough, another reality becomes visible. What seems familiar can become an illusion that exposes hidden contradictions and systems of power and extraction.

In Sandbag Castle, the image of a sandcastle is transformed into a defensive structure. What appears to be sandbags is actually concrete. The material we rely on for our protection is simultaneously contributing to the problem we are trying to protect ourselves against.

Mak does not simply point out what is going wrong. By subtly shifting our perspective, she invites us to look again and question what we have come to take for granted. Sandbag Castle places the climate question not in a distant future, but in the present. The problem is here. The possibilities are here. The future is now.