Trinity College Dublin Prints Ireland's First Cement-Free Geopolymer Building Element

From Industrial Waste to Building Material

Researchers at Trinity College Dublin's School of Engineering, working with construction technology firm Harcourt Technologies Ltd. (HTL.Tech), have demonstrated Ireland's first cement-free, 3D printed geopolymer. The red-brown material is made largely from bauxite refining residue — an industrial waste product that would otherwise require treatment, long-term storage, or landfill disposal.

Two Environmental Wins

The geopolymer delivers two environmental benefits simultaneously: it eliminates the need for Portland cement, which is responsible for roughly 8% of global CO2 emissions, and it creates a high-value use for industrial residues that would otherwise be waste. Preliminary assessments suggest the material could reduce embodied carbon emissions by approximately 70% compared to conventional Portland cement concretes.

"Broadly speaking, this successful trial demonstrates how local industrial residues can be transformed into functional, adaptable and visually distinctive construction materials," said Professor Sara Pavia, who led the research alongside Dr. Zehao Lei.

From Lab to Factory Floor

The trial, conducted at HTL.Tech's facility, confirmed that the geopolymer could be mixed, pumped, extruded, and printed using standard 3D concrete printing equipment. The material's composition, rheology, setting behavior, and early-age performance can be tailored to different manufacturing processes and construction applications.

A consortium led by SISK — with partners FLI Precast Solutions, McGrath Quarries, Techcrete, and Roadstone — is now working to scale the material from laboratory batches to the volumes and consistency required for industrial equipment. The next phase will focus on mechanical performance, durability, reinforcement, long-term stability, process control, and regulatory compliance.

What Is a Geopolymer?

Geopolymers are inorganic polymers formed by reacting aluminosilicate sources with alkaline activators. Unlike traditional cement, which relies on calcium silicate hydration, geopolymers use industrial by-products like fly ash, slag, or in this case, bauxite refining residue. The result is a durable, fire-resistant, chemically stable binder that can be 3D printed into complex geometries without molds or formwork.