Geopolymers are increasingly gaining attention in the construction industry as a low-carbon alternative to traditional cement-based concrete. Widely used in the manufacture of construction products, these materials are seen as a key solution for reducing the carbon footprint of buildings and infrastructure. However, questions have remained around their suitability for colouring, an important requirement as customers demand more customised and visually appealing products.

To address concerns around colour performance and durability, pigment specialists from LANXESS and Harold Scholz & Co. GmbH, together with Rhein-Chemotechnik GmbH, recently undertook a joint research project examining the colouring behaviour of geopolymer systems. The study focused on the use of iron oxide pigments and compared results across alkali-activated materials, specialised geopolymers and conventional cement-based products.

The research highlighted key differences between calcium-rich alkali-activated materials and low-calcium geopolymers produced from metakaolins. While alkali-activated systems form calcium silicate hydrate phases that allow strong electrostatic binding of pigments, geopolymers develop a three-dimensional network structure that interacts differently with colourants. Despite these chemical differences, test results showed that all binder systems could be coloured effectively and durably.

Samples produced under DIN EN 12878 standards demonstrated stable coloration, even after exposure to natural and accelerated weathering. Although variations were observed in mixing, processing and curing behaviour, the durability and visual quality of the colouring remained consistent across all systems.

The findings confirm that geopolymers and alkali-activated materials can meet aesthetic demands without compromising performance. Further research, involving the Technical University of Dresden, is planned to examine structural characteristics and long-term technical performance in greater detail.