As the construction sector faces intense pressure to reduce carbon emissions, traditional Portland cement, a major contributor to global CO2, has become a prime target for replacement.
In a joint article published in Concrete magazine, “Characterisation of low-carbon AACM concrete and mortar,” C-Probe Systems’ Graeme Jones and Mott MacDonald’s Paul Lambert dive into 20 years of research from Sheffield Hallam University. Their findings prove that Alkali-Activated Cementitious Materials (AACMs) are not just a green alternative, but a high-performance upgrade for structural repair, protection, and new-build applications.
AACMs (including geopolymers) are inorganic cements manufactured predominantly from recycled materials and industrial by-products. When combined with an alkaline activator, the mixture forms a crosslinked structural framework.
The resulting hardened material offers the mechanical versatility of standard concrete alongside the unique resilience of advanced ceramics—all while significantly shrinking the asset’s carbon footprint.
The mechanical traits of AACM concrete are highly predictable. Research shows a direct linear correlation between binder content and strength, making it incredibly simple to formulate a range of targeted products, from low-strength pointing mortars to ultra-high-strength repair materials.
While high-binder materials typically raise concerns regarding drying shrinkage and micro-cracking, long-term testing demonstrates that AACMs naturally compensate for shrinkage upon hardening. In field tests, such as unreinforced parking apron patches exposed to traffic and weather for over 12 months, the material remained entirely intact, perfectly bonded, and free of any visible cracking.
Beyond structural strength, the chemical formulation of AACMs can be altered to fit specific environmental challenges:
Extreme Fire Resistance: Tested at temperatures reaching 1200°C for up to five hours (in accordance with BS EN 1363-1), precast slabs retained their integrity without disintegrating, shielding the unexposed side from heat transference.
Extreme Cold Tolerance: The material’s unique chemistry allows for successful sub-zero installations, proven commercially by applying anode mortars within masonry bed joints at ambient temperatures as low as -15°C.
Electrical Conductivity for Corrosion Control: By incorporating a specialized conductive additive, an inherently non-conductive binder can be modified into an impressed current cathodic protection (ICCP) anode. Lowering electrical resistivity allows the material to distribute low-voltage protective currents, preventing steel corrosion in both modern reinforced concrete and heritage steel-frame buildings.
Whether used as a sprayed concrete anode on a historic facade in Kansas City or precast structural segments on a marine quayside, AACMs provide a durable, sustainable framework that completely replaces the need for traditional Portland cements.
