A new geopolymer concrete developed entirely from industrial and construction waste has demonstrated outstanding resistance to extreme temperatures, offering a lower-carbon alternative to Portland cement while maintaining its structural integrity after exposure to fire.
Geopolymer concrete made from waste offers a low-carbon alternative to Portland cement
Concrete is the world’s second most widely used material after water, but its main ingredient, Portland cement, is responsible for around 7-8% of global CO₂ emissions. Producing Portland cement requires limestone and clay to be heated to approximately 1,400°C, making it one of the most energy-intensive industrial processes.
Researchers at Kaunas University of Technology (KTU) in Lithuania have investigated an alternative based on geopolymer concrete, using waste-derived binders that can be produced at much lower temperatures while eliminating the need for virgin raw materials.
Waste-derived geopolymer concrete delivers impressive fire resistance
The Lithuanian research team replaced Portland cement with geopolymer binders produced from crushed ceramic brick waste and metakaolin residues, combining them with five different fine aggregates: sand, granite, basalt, ceramic waste and corundum.
After exposure to temperatures of 800°C, the highest-performing mixtures achieved compressive strengths of 34.7 MPa and 53.0 MPa, while showing only limited microcracking.
A compressive strength of 53 MPa means the material can withstand a load of roughly 530 kilograms per square centimetre before failure, demonstrating excellent structural performance even after severe thermal exposure.
Why geopolymer concrete performs better than Portland cement
When construction materials are heated to around 800°C, thermal expansion creates internal stresses that typically generate microscopic cracks and significantly reduce structural strength.
The limited microcracking observed in the Lithuanian geopolymer mixtures indicates excellent thermal stability and resistance to thermal shock, allowing the material to retain much of its structural integrity.
By comparison, conventional Portland cement concrete generally suffers substantial strength losses under similar conditions, making geopolymer concrete a promising solution for structures exposed to fire or high operating temperatures.
“In buildings and industrial facilities there are areas where concrete literally operates in close contact with fire, such as around chimneys, boilers, furnaces, tunnels and high-temperature equipment,” explained Professor Vaičiukynienė, who led the research.
“These applications require materials that not only resist burning but also retain their strength after exposure to extreme temperatures, and this is precisely what these geopolymer mortars are designed to achieve.”
Construction waste becomes the raw material for geopolymer concrete
Beyond its mechanical performance, one of the main advantages of the material is its environmental profile.
The geopolymer binder is produced entirely from construction and industrial waste. Ceramic bricks recovered from demolition sites are crushed and processed together with metakaolin, a reactive clay-based material obtained from waste generated by a Lithuanian glass manufacturing facility.
The approach avoids the extraction of new natural resources while promoting the recycling of industrial by-products and construction waste within a circular economy framework.
Commercial adoption still faces regulatory barriers
Despite growing scientific interest, geopolymer concrete remains largely absent from mainstream construction.
The main obstacle is the lack of harmonised technical standards and regulations governing its use. Economic considerations and market inertia also slow adoption, as the mature Portland cement industry continues to dominate the sector and concrete manufacturers remain cautious about introducing innovative materials that could expose them to legal and financial risks if performance standards are not yet fully established.
Meanwhile, the KTU research team continues to test the fire performance of its geopolymer mortar, with the aim of securing a European patent.
