The CO₂ problem with concrete comes from Portland cement. Geopolymer concrete eliminates it entirely: instead of cement, it binds aggregates using alkali-activated aluminosilicate materials — typically fly ash (a coal-power by-product) or ground granulated blast-furnace slag — turning industrial waste into a durable binder with up to ~80% lower embodied carbon.
Working principle
An aluminosilicate source (fly ash/slag) is mixed with an alkaline activator (sodium hydroxide and/or sodium silicate). The alkali dissolves silicon and aluminium from the precursor, which then polymerise into a three-dimensional aluminosilicate network — the 'geopolymer' gel — that hardens and binds the aggregate. This reaction differs fundamentally from cement hydration and yields a matrix with high acid, fire and chemical resistance.
| Property | OPC concrete | Geopolymer |
|---|---|---|
| Binder | Portland cement | Activated fly ash / slag |
| CO₂ footprint | High | Up to ~80% lower |
| Acid / heat resistance | Moderate | Excellent |
| Challenge | Emissions | Activator handling, supply |
Why it mattersGeopolymers turn a waste disposal problem (fly ash, slag) into a high-performance binder — though caustic activators and variable feedstock quality complicate site use.
Applications
- Precast elements, pavements and marine structures
- Acid- and fire-resistant industrial flooring
- Sustainable infrastructure with embodied-carbon targets
References & further reading
- Davidovits, “Geopolymers: Inorganic polymeric new materials,” J. Thermal Analysis, 1991.
- Provis & van Deventer (eds.), “Alkali Activated Materials,” RILEM, 2014.
- Duxson et al., “Geopolymer technology: the current state of the art,” J. Materials Science, 2007.