Taisei T-eConcrete Zero-Cement and Carbon-Recycling Concrete

Taisei Corporation is a Japanese general contractor that develops low-carbon construction materials as part of its goal of carbon neutrality by 2050. Its T-eConcrete line tackles the emissions of portland cement by replacing it with industrial by-products such as ground granulated blast furnace slag and fly ash, and in its most advanced form by fixing captured CO2 inside the concrete.

The lineup has four types: a Building Standards Law compliant type with partial slag replacement, a fly ash type, a Zero-Cement type that activates slag without any portland cement, and a Carbon-Recycling type. In the Carbon-Recycling type, captured CO2 is injected into a calcium solution to make calcium carbonate, which is mixed with slag, aggregates and additives at an ordinary ready-mix plant without special equipment. Applications include cast-in-place concrete, T-eCon shield tunnel segments, culverts, paving blocks and T-razzo stone-like finishes for public infrastructure and building owners.

• Standard-compliant type: partial cement replacement with ground granulated blast furnace slag for regulated buildings.
• Fly ash type: combines slag and fly ash from coal power plants to cut cement content.
• Zero-Cement type: slag with activators and no portland cement, reducing CO2 by up to 80%.
• Carbon-Recycling type: calcium carbonate from captured CO2 fixes carbon inside the concrete for net-negative emissions.
• Ready-mix compatible: produced with ordinary mixers and placed by normal cast-in-place methods.
• Precast products: T-eCon tunnel segments, culverts, invert blocks and T-razzo stone-like finishes.

Metro, tunnel and expressway projects in Vietnam can specify zero-cement tunnel segments and culverts to lower embodied carbon. Steel mills and coal power plants can partner with precast producers to use slag and fly ash in T-eConcrete mixes. Industrial park developers can use carbon-recycling paving and blocks for low-carbon site works.

The Zero-Cement type can reduce CO2 by up to 80%, while the Carbon-Recycling type absorbs 98 to 171 kg of CO2 per cubic metre for a net balance of minus 45 to minus 116 kg. On the Hanshin Expressway trial the mix reached 30.8 N/mm2 against a 27 N/mm2 design strength with net emissions of minus 20 kg per cubic metre. Strength of 20 to 45 N/mm2 and slump comparable to ordinary concrete allow production at standard ready-mix plants.

Public infrastructure owners in Japan and Asia are beginning to require low-carbon concrete in tenders, and slag and fly ash from steel mills and coal plants are abundant in the region. Vietnam produces large volumes of blast furnace slag and fly ash, and Japanese contractors active in Vietnamese infrastructure are well placed to transfer zero-cement and CO2-fixing concrete technologies.

Taisei Corporation is a major Japanese general contractor targeting carbon neutrality by 2050. T-eConcrete received the JSCE Environmental Award in 2014 and the 13th ENAA Engineering Commendation Award in 2021, and the Hanshin Expressway pour won an Encouragement Prize at the FY2024 Kinki Construction Recycling Awards. Developed with the T-eConcrete Research Group.