US: Researchers at Washington State University (WSU) have developed a method for making low-carbon concrete using cement and biochar, a type of charcoal made from organic waste that is nearly as strong as standard concrete. The team, led by doctoral student Zhipeng Li, strengthened the biochar with concrete wastewater. The biochar was able to suck up to 23% of its weight in carbon dioxide from the air.

Previous attempts to add biochar as a substitute in cement have significantly reduced the strength of the resulting concrete. However, the WSU project found that by treating the biochar with concrete washout wastewater it was able to add up to 30% biochar to cement mixtures. The paste made of the biochar-amended cement was able to reach a compressive strength after 28 days comparable to that of ordinary cement. The researchers used calcium in the concrete washout water to induce the formation of calcite, which benefits the biochar and, eventually, the concrete that incorporates it.

Xianming Shi, professor in the WSU Department of Civil and Environmental Engineering, said, “We’re very excited that this will contribute to the mission of zero-carbon built environment.” He added, “Most other researchers were only able to add up to 3% biochar to replace cement, but we’re demonstrating the use of much higher dosages because we’ve figured out how to engineer the surface of the biochar.”

The synergy between the highly alkaline wastewater that contains a lot of calcium and the highly porous biochar meant that calcium carbonate precipitated onto or into the biochar, strengthening it and allowing for the capture of carbon dioxide from the air. A concrete made of the material would be expected to continue sequestering CO2 for the lifetime of the concrete, typically 30 years in pavement or 75 years in a bridge.

The researchers have been working with the WSU Office of Commercialization to protect the intellectual property and have filed a provisional patent application on their carbon-negative concrete work. They recently received a seed grant from the Washington Research Foundation to produce more data for a variety of use cases. They are also actively seeking industry partners from the building and construction sector to scale up production for field demonstrations and licensing this WSU technology.

US: A team from the Massachusetts Institute of Technology (MIT) has developed a new method to sequester CO₂ in concrete before curing it. The method is based on the addition of bicarbonate of soda, which reacts with cement to produce a calcium carbonate-calcium silicone hydrate composite. The Journal of Engineering has reported that the method adds the benefits of CO₂ mineralisation during production and casting, doubling the mechanical performance of early-stage concrete. It also eliminates the effects of carbonation reactions in cured concrete, which weaken the concrete by lowering its alkalinity, which accelerates the corrosion of rebar. The method has the potential to sequester 15% of CO₂ emissions from cement production.

The team said “The pre-curing capacity of concrete to sequester CO₂ has been largely underestimated and underutilised. Our new discovery could further be combined with other recent innovations in the development of lower carbon footprint concrete admixtures to provide much greener, and even carbon-negative, construction materials.”

Finland: VTT Technical Research Centre subsidiary Carbonaide has concluded its seed funding round, having raised funds worth Euro1.8m. Lakan Betoni, which produces precast and ready-mix concrete, led the funding, along with utilities provider Vantaa Energy. Carbonaide will use the funds to build an industrial pilot plant for its carbon neutral precast concrete product at an existing precast concrete plant in Hollola. The plant will bind captured CO₂ in the product at atmospheric pressure. The process generates 50% lower CO₂ emissions than precast concrete production using ordinary Portland cement (OPC). Suitable raw materials include ground granulated blast furnace slag (GGBFS), green liquor dregs and bio-ash. In trial production, the use of GGBFS gave Carbonaide's concrete a negative carbon footprint of -60kg/m³.

Other sources of loans and in-kind contributions included Finnish state innovation fund Business Finland.

Poland: Switzerland-based Holcim has acquired precast concrete producer HM Factory. HM Factory supplies precast concrete products manufactured in Poland to the Scandinavian export market. It employs 70 people across its operations.

Holcim’s Europe regional head Miljan Gutovic said “HM Factory is a perfect complement to our existing operations, offering multiple technological and raw material synergies. I look forward to welcoming the employees of HM Factory, whose expertise will be invaluable in accelerating green growth, especially in highly efficient modular construction.”