Taisei’s Carbon_Recycled Concrete (T-eConcrete®/Carbon-Recycling)

Enhancing the lineup of T-eConcrete®, an environmentally friendly concrete, as well as effectively utilizing resources and realizing decarbonization

In order to achieve carbon neutrality by 2050, efforts are underway to “carbon recycle” to curb CO2 emissions by recovering and effectively utilizing CO2 as a resource.
Taisei Corporation has developed various types of environmentally friendly concrete, its T-eConcrete®, and is committed to the effective use of resources and decarbonization.
Going forward, we aim to be a front-runner in the environmental sector and will accelerate our efforts to become carbon neutral by accumulating experience in applications for concrete that “creates the future.”

Characteristics and Variations of T-eConcrete®

T-eConcrete® limits the amount of cement used, maintains the same strength and workability as ordinary concrete and is also able to reduce CO2 emissions.

There are four types, depending on the mixture conditions for such items as industrial by-products added in place of cement: Japanese Building Standards Law compliant type, Fly ash utilization type, Zero-Cement type, and Carbon-Recycling. Depending on the intended use, concrete of appropriate specifications can be developed.

  • Building Standards Law compliant type
    Reducing cement, the binder replaces that with ground granulated blast furnace slag (GGBFS) (discharged as an industrial by-product at steelworks).
    It is suitable for building construction that complies with Japan’s Building Standards Law.
  • Fly ash utilization type
    Reducing cement, the binder replaces that with ground granulated blast furnace slag (GGBFS) and fly ash (a type of coal ash).
    Coal ash, an industrial by-product of coal-fired power plants, can be effectively utilized.
  • Zero-Cement type
    Without using any Portland cement, this type is made using ground granulated blast furnace slag (GGBFS) and special additives as activators or stimulators.
    It enables a maximum amount (up to 80%) of CO2 reduction.
  • Carbon-Recycling
    Without using any Portland cement, this type is made using carbon-recycled materials such as calcium carbonate, and ground granulated blast furnace slag (GGBFS) and special additives as activators or stimulators.
    By absorbing CO2 internally within the concrete, there are negative CO2 emissions (balance of absorption and emission).

T-eConcrete® variations (CO2 emissions rate, progress status)

環境配慮コンクリート/T-<i>e</i>Concrete®シリーズ

 
From among these, we will introduce in detail the characteristics of T-eConcrete®/Carbon-Recycling,which uses CO2 as a resource.

What Is T-eConcrete®/Carbon-Recycling (Carbon _Recycled Concrete)?

Carbon-recycled concrete is manufactured using carbon-recycled materials such as calcium carbonate, which is produced by reacting calcium with CO2 captured from exhaust gases, and ground granulated blast furnace slag (GGBFS), an industrial by-product of steel manufacturing. CO2 can be absorbed inside the concrete by converting CO2 into calcium carbonate and mixing it into the concrete.

Absorbing 70–170kg of CO2 per 1m3 of concrete

Negative balance of -55kg to -5kg per 1m3 of concrete (result based on trial balance of CO2 recovery and emission)

Strength characteristics (compressive strength: 20–45N/mm2) and flowability (slump: 12–21cm, slump flow: 45–60cm), which is an indicator of workability, are equivalent to those of ordinary concrete, and can be manufactured at ordinary ready-mixed concrete plants without special equipment.

Able to maintain strong alkaline inside concrete, prevents corrosion of re-bars and maintains durability of reinforced concrete structures

Example of balance between CO2 absorption and emissions

If CO2 is absorbed by manufacturing calcium carbonate from CO2 captured from exhaust gases, with the amount of CO2 absorbed in calcium carbonate stated as A = 100kg, and the amount of CO2 emitted into the air during the manufacturing process of calcium carbonate stated as B = 50kg, then the balance of CO2 emissions from calcium carbonate used for concrete is B-A = -50kg.

Carbon-recycled concrete cross-sections

カーボンリサイクル・コンクリートの断面

T-eConcrete®/Carbon-Recycling Manufacturing Process and Status

Manufacturing process

製造方法
  • Inject the captured CO2 into an aqueous solution in which calcium is dissolved to produce calcium carbonate absorbed with CO2
  • Add aggregates such as sand and gravel, together with water and additives, to blast furnace slag and calcium carbonate with absorbed CO2
  • Mix the added ingredients in a mixer
  • T-eConcrete®/Carbon-Recycling (carbon-recycled concrete) is completed

Manufacturing status

  • *Link to YouTube.

Information on viewing lecture archives

  • *Link to YouTube.
Lecturer name Nikkei SDGs Festival, Green Architecture
A Materials Revolution That Is Transforming Society, On-Site Manufacturing of “CO2 Recycle Concrete”

Application Case Studies / External Awards

Application case study (carbon-recycled concrete)

Interior wall components of experimental facility

実験施設内部壁部材

Cast-in-place pavement (red box) and stone-like paving blocks (blue box)

現場打ち舗装(赤枠内)および石材調舗装ブロック(青枠内)

Application case study (Zero-Cement type)

Applied as cast-in-place concrete

土間コンクリートへの適用
Cast-in-place concrete (red box)

Concrete products manufactured by members of T-eConcrete® Research Group

Civil engineering structures
T-eCon®/Segment for shield tunnel
T-eCon®/Culvert
Shield tunnel invert block
T-razzo®; Stone-like building materials

External stairway
Building entranceway

External awards