Concrete is the most widely used construction material in the world. We generally make concrete using ordinary portland cement (OPC), water, and aggregates, including fine sand and coarse gravel.

OPC is responsible for most of the properties of concrete. OPC manufacturing is energy intensive and environmentally harmful, leading to a high carbon footprint for this ubiquitous construction material. Production of 1 tonne of OPC is estimated to emit approximately 1 tonne of carbon dioxide in the air.¹ This is caused by calcination of limestone, which releases carbon dioxide, and the associated energy costs to grind and sinter raw materials at less than 1,600°C.