Eco-Friendly Binder with a Timer: BelSU’s Breakthrough in Sustainable Construction

Traditional Portland cement is strong but carries a heavy carbon footprint. A greener alternative is alkali-activated binders made from ground blast-furnace slag. However, these materials are notoriously difficult to work with. Wet-milled mixtures set almost instantly, while dry-milled versions can take frustratingly long to harden.

The team at Belgorod National Research University (BelSU), led by Ivan Nikulin, Director of the BelSU Engineering Centre, in collaboration with colleagues from Belgorod Shukhov State Technological University, have solved this problem. Their solution involves adding citrogypsum – a fine powder formed during the microbiological synthesis of citric acid using the mould Aspergillus niger – to the mix.

The technology involves grinding blast-furnace slag into an ultrafine powder and adding citrogypsum at just 1.5–2.5% by weight. Laboratory tests showed this small addition cuts the initial setting time by 40-51% while keeping the process fully controllable. By adjusting the dosage, builders can speed up hardening for urgent repairs or slow it down to allow more time for transporting mortar.

Crucially, this control comes without sacrificing strength. The final material achieves a compressive strength of 28.7-32.8 megapascals, comparable to standard Portland cement (CEM 32.5).

“This balance was previously unattainable,” Nikulin explained, noting the material could be used for plaster, paving slabs, and stairways.

The development solves a fundamental problem for eco-friendly binders while finding a practical use for large volumes of industrial waste. The work was supported by the Ministry of Higher Education and Science of Russia under state contract No. FZWG-2024-00-01 and is protected by Russian patent No. 2861432.