The Eco Edit – Geopolymers: concrete solution to high-emission cement

Maeve Windle – Contributed

Concrete is the second most-consumed resource on Earth after water, with an estimated 30 billion tonnes used every year.

While that figure may seem staggering, it reflects concrete’s essential role in modern life. It forms the foundations of our homes, roads, sidewalks, bridges, dams, industrial floors, and countless other structures.

Demand is expected to rise by as much as 25 percent over the next decade. Beyond concerns about urban sprawl and construction-related pollution, this growing reliance on concrete carries a significant environmental cost.

Cement, the binding ingredient in concrete, is responsible for approximately eight per cent of global human-caused carbon dioxide emissions.

As climate change accelerates and the need to reduce emissions becomes increasingly urgent, investing in sustainable, low-emission building materials is more important than ever.

Much of concrete’s carbon footprint stems from the production of Ordinary Portland Cement (OPC), the most widely used cement in the world.

A key ingredient in OPC is limestone, which provides the calcium oxide necessary for the chemical reactions that bind concrete together. During manufacturing, limestone undergoes calcination, a process in which it is heated to extremely high temperatures. This releases carbon dioxide and isolates the lime needed for cement production. Calcination accounts for roughly 90 per cent of cement’s carbon footprint and results in the release of approximately 0.5 to 1 tonne of carbon dioxide for every tonne of OPC produced.

Reducing emissions from cement manufacturing is therefore essential to achieving meaningful reductions in global greenhouse gas emissions.

One promising solution is the use of geopolymers.

These strong, ceramic-like materials possess many of the same physical properties as conventional cement but do not require calcination and can often be produced using industrial byproducts. As a result, geopolymer concrete has the potential to reduce emissions associated with cement production by 70 to 90 percent through the partial or complete replacement of limestone-based binders. With the addition of specialized additives, some geopolymer formulations may even become carbon negative.

Geopolymers offer several additional advantages. Their unique chemical composition makes them more resistant to environmental degradation, potentially extending service life by 50 to 100 years compared with traditional OPC-based concrete. They can also be crushed and reused to create new concrete products, improving recyclability. Furthermore, the three-dimensional polymer network formed during curing often provides greater compressive and flexural strength than conventional concrete.

Given these benefits, it is reasonable to ask why geopolymer concrete has not yet become the industry standard. Challenges include higher production costs, the need for further research and testing, and the difficulty of replacing a material that has dominated construction for nearly two centuries. However, as public awareness of concrete’s environmental impact grows and interest in sustainable alternatives increases, geopolymer technology offers a promising path toward a greener and more resilient future.