Low carbon concrete
Concrete, the most widely used construction material worldwide, significantly contributes to carbon emissions, primarily due to the use of Portland cement. Cement and concrete production generate about 8% of global emissions annually, positioning cement manufacturing as the largest industrial source of carbon pollution.
Low carbon concrete aims to minimise the environmental impact of construction by reducing the amount of concrete needed through design and reducing reliance on traditional Portland cement used in concrete manufacture. It incorporates innovative materials and manufacturing methods to lower emissions without compromising strength or durability.
Work undertaken by the Materials and Embodied Carbon Leaders’ Alliance (MECLA) has sought to define and provide guidance to government and industry on low carbon concrete, how to measure and specify its use.[i] The figure and tables below illustrate different Environmental Product Declarations (EPD) carbon intensities for different concrete strengths and mixes.
MECLA states that: Low carbon concrete should have the lowest embodied carbon available for the application while still meeting all specified technical and performance requirements. It must meet the requirements of AS 1379 to ensure compliance with the design of concrete structures regarding service life, as outlined in AS 3600, AS 5100.5, and any government standards used for concrete structures.
MECLA's guide to low-carbon concrete - Version 1, Revision Number: 3 (final draft)
Application of low carbon concrete will depend on a number of elements including availability, cost, location, and asset type. Some examples of low carbon concrete types and applications are provided below.
Geopolymer concrete
A binder system that uses industrial by-products, such as fly ash (FA) or ground granulated blast furnace slag (GGBFS), as sources of aluminosilicates activated by alkali solutions, instead of Portland cement. The use of geopolymers reduces the consumption of carbon-intensive Portland cement and diverts industrial by-products stockpiled in landfills
Applications include general construction and marine environments.
Non-Portland cements
Non-Portland cement alternatives, such as calcium sulfoaluminate or magnesium-based cements, reduce emissions by eliminating the reliance on Portland cement. These alternatives require lower production temperatures, which saves energy and further decreases environmental impact.
These cements are usually used for specialised constructions with unique durability needs.
Supplementary cementitious materials
Supplementary cementitious materials (SCMs) such as FA, GGBFS and silica fume, which partially replace Portland cement in concrete. By lowering the clinker content, these materials reduce the proportion of cement in the mix, while enhancing durability to extend the lifespan of structures and reduce lifecycle emissions.
Applications include general construction, pavements, and large-scale infrastructure.
Extruded hollow concrete
Thin-walled, lightweight precast elements with optimised material usage reduce material demand, thereby lowering carbon emissions, transportation energy, and handling energy requirements.
Extruded hollow concrete may be used for beams, pipes, panels, and structural supports.
Precast concrete
Fabricated off-site under controlled conditions, minimising waste and improving energy efficiency. Precast elements can also incorporate low carbon materials.
Applications include modular construction, bridges, and infrastructure.
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References
1. MECLA's guide to low-carbon concrete - Version 1, Revision Number: 3 (final draft)
2. Lin, Y, Maghool, F, Arulrajah, A & Horpibulsuk, S 2024, Feasibility of recycled concrete aggregate stabilized with one-part geopolymers as semi-rigid inclusion columns, Construction and Building Materials, 424, p.135825.
3. VDZ 2021, Decarbonisation pathways for the Australian cement and concrete sector, Cement Industry Federation.
4. Hanein, T, Dee ka Tirrem A, G, Zhang, Z & Provis, J, Alternative non-Portland binders.
5. Hall, B, Grenfell, J, Pandelidi, C, Yaghoubi, J, Chaudry, U, Lyons, M, O'Connor, G, Harrison, J & Feigen, D 2022, Best practice expert advice on the use of recycled materials in road and rail infrastructure: part A technical review and assessment.
6. Hall, B, Grenfell, J, Pandelidi, C, Yaghoubi, J, Lyons, M, O'Connor, G, Harrison, J, Feigen, D & Xue, S 2022, Best practice expert advice on the use of recycled materials in road and rail infrastructure: part B sustainability impacts report.