The solution Low carbon sustainable concrete is typically integrated with:

Sustainable concrete, low carbon construction, circular economy

Building envelope solutions 

Envelope insulation 

Passive building solutions 

Passive building design strategies (building shape, plan, orientation, shading system…) 

Low-carbon and sustainable building materials 

Reducing embedded emissions of buildings 

Integrated solutions 

Positive Energy Buildings/Houses 

Nearly Zero Energy Buildings 

Management of municipal solid waste (MSW) 

Waste valorisation 

Recycling centres 

Construction and Buildings 

Optimal management of waste at the end of building life cycle 

Re-using local building waste (e.g. local waste material bank) 

Urban mining model to assess circular construction opportunities and optimize resource use and exchange 

BOB database: Online register with building and infrastructure material/parts/products for reuse/circular use 

Other circular products  

Reduction of raw materials, waste and integration of secondary materials 

Urban carbon storage and sequestration 

Algae Cultivation for Carbon Capture 

CCS/CCU 

Other carbon dioxide capture and storage (CCS) 

Carbon dioxide capture and utilisation (CCU) 

Preconditions 

• Technical aspects/infrastructure: A change to a system of harmonized performance-based technical specification can accelerate the adoption and acceptance of new low carbon construction materials using different feedstock [6]. 

• Policy and regulatory/legal framework:  

• Amending existing standards and codes is required because construction materials must typically meet composition-based and performance-based codes and standards for use. This will allow the use of cements based on alternative binding materials such as BYF cement (in Europe), concrete with recycled concrete waste, cement with SCMs such as carbonated recycled cement paste, concrete with synthetic aggregates. 

• Co-processing must be recognized in framework waste legislation [7]. 

• Policies should facilitate waste shipment between EU countries, discourage landfill and prohibit exports of waste outside of the EU [2]. 

• Funding and financing: Incentives for the use of recycled building materials should be created for customers [3]. 

Enabling conditions 

• Technical aspects/infrastructure  

• The re-carbonation of built concrete products (its ability to uptake CO2 from the atmosphere) over their life cycle should be recognised in CO2 emissions accounting, carbon footprint methodologies, and CO2 certification removal schemes [2]. 

• The design of low carbon concrete should take into account all the embodied carbon in the material [6]. 

• The use of digitalisation across the concrete industry: Data for cement and concrete can be available to determine the carbon footprint of the construction material or building and to show the source of the materials used in construction [2] 

• Policy and regulatory/legal framework:  

• Extending actions down the value chain to the final customer. Emission Trading System based only on clinker is not efficient as it affects only the minor part of the value chain [11]. Mandates that require buildings and infrastructure to be constructed only using cement that has a very low green house gas (GHG) footprint has the potential for large additional reduction in CO2 [8] or bans or restrictions on the use of cement with only virgin materials. 

• Introduction of guidelines that mandate public procurers to only purchase cement and derived products with close-to-zero CO2 emissions [1]. These regulations should be standardised beyond national borders.  

• Policies can incentivise the use of digitalisation across the concrete industry [2]. 

• Funding and financing: 

• The production and use of quality recycled CDW must be incentivized as well as the production of building materials containing recycled content and industrial waste. This could provide an economic advantage for using recycled material steering the value-chain towards a more circular and sustainable economy.   

• Tax penalties on conventional products with a high GHG footprint. Taxes on virgin materials. 

• Access to EU/public funding and innovation procurement can further incentivise the development of R&I solutions for low carbon building materials, transforming waste into resources and promoting a circular economy.   

• Economic and social context:  

• Affordable low carbon construction materials for housing solutions must be at the heart of housing policies [7]. 

• Industry should promote international training events with national standardisation bodies and accreditation institutes, researchers and students to educate and inform the public and key stakeholders and to build social acceptance. This includes training for architects/engineers on the applicability of lower-carbon concrete mixes and training for engineers and contractors to use different types of low carbon cement and to get a better understanding of sustainability issues related to building materials 

• Project governance and implementation modalities:  

• Carbon pricing mechanisms must be designed to target value chains and be embedded in holistic climate policy frameworks in order to create demand for low-carbon concrete innovations. 

• Through investment, mechanisms that use private funding for low carbon innovative technologies and through the promotion of private-public partnerships, the governments can mitigate the risks associated with the deployment of the innovative technologies. Horizon 2020 and the Innovation Fund are such examples that help attract private investment.  

• The use of co-creation methods: collaborations with public authorities at the design stage of projects, can find the best low carbon building material solutions with optimized costs, durability, sustainability performances  

• Trade and climate policy frameworks need to be mutually reinforcing [7]. 

• Product design policies product labelling or voluntary certification systems [9]. Labels indicating the environmental characteristics or other beneficial aspects of products can help to create or increase demand for such products. Development of standardized and transparent assessment methods, such as life cycle assessments (LCA) [6]. 

• Citizen-engagement initiatives to raise and maximise the chances of take-up. Rapid creation of necessary framework conditions that lead to increasing environmental awareness and may also lead to market acceptance. 

• Technical aspects/infrastructure  

• Lack of established standards 

• The integration of these new binders into existing or new standards at national or European level is a challenge, especially in terms of time  

• Lack of performance data 

• Lack or low access to material flows from concrete demolition because of "downcycling" of the material or even final disposal in landfills or export outside of the EU 

• Insufficiently developed supply chains 

• Policy and regulatory/legal framework “carbon leakage” - EU producers are at a competitive disadvantage compared to non-EU producers that are not obliged to buy Emissions Trading System allowances [8]. 

• Funding and financing limited access to finance for small and medium sized enterprises (SMEs), start-ups is considerable and they face heavy competition from major construction companies [6].  

• Economic and social context  

• Higher costs relative to conventional benchmark products. Novel technologies for separation and carbonation naturally also require high investments in plant, accompanied by rising costs for such novel, resource and environmentally friendly products making it prohibitively expensive for some customers. 

• Less attractive from the economic standpoint considering the demands on speed of construction meaning low-carbon mixes are not favoured. 

• Small industries producing alternative low carbon solutions cannot compete against established industries economies at scale [6]. 

• Project governance and implementation modalities  

• The implementation of such low carbon concrete solutions can face the very conservative attitudes towards new technologies in the construction industry  

• Lack of awareness and practical knowledge among specialists [10] 

• Negative perception held by other professionals [10] 

• Client acceptance [10] 

• Low availability of skilled labour [10] 

• The possibility and responsibility to implement low carbon concrete to reduce CO2 emissions is spread across different segments of the value chain with diverging incentives [10] 

• Too time consuming to design with, lack of design guides and tools, lack of confidence in contractor ability to deliver a new design, perceived concerns about material sourcing prevent selection [10] 

• Difficulties obtaining insurances for novel and reused materials [10] 

Literature 

1. International Energy Agency and World Business Council on Sustainable Development - Cement Sustainability Initiative,  Technology Roadmap Low-Carbon Transition in the Cement Industry, 2018 

2. Cembureau, Cementing the European Green Deal, Reaching climate neutrality along the cement and concrete value chain by 2050, 2021 

3. K. L. Scrivener, V. M. John, E. M. Gartner, Eco-efficient cements: Potential, economically viable solutions for a low-CO2, cement-based materials industry, United Nations Environment Programme, 2016 

4. C. Shi, J.Provis, Recent progress in low-carbon binders, Cement and Concrete Research, 2019, pag. 227-250  

5. Gartner, E., 'Industrially interesting approaches to 'Low-CO2' cements,' CCR,34, 1489-1498, 2004 

6. B. Olfe-Kräutlein Push or Pull? Policy Barriers and Incentives to the Development and Deployment of CO2 Utilization, in Particular CO2 Mineralization, POLICY AND PRACTICE REVIEWS, 2021 

7. LafargeHolcim Ambition, 2019 

8. International Energy Agency, Deployment of bio-CCS in the cement sector: an overview of technology options and policy tools, 2021 

9. Ecorys, The role of market-based instruments in achieving a resource efficient economy, 2011 

10. J. Giesekam, John R. Barrett & Peter Taylor: Construction sector views on low carbon building materials, Building Research & Information, 2015, DOI: 10.1080/09613218.2016.1086872  

Websites 

11. LC3 – Limestone Calcined Clay Cement 

12. Lafarge Project Aether® - A new avenue for cement CO2 mitigation (globalcement.com) 

13. 06132016-press-lafargeholcim_sustainability_report_print_2015.pdf 

14. Solidia® – Making Sustainability Business As Usual℠ (solidiatech.com) 

15. Carbon8 

16. https://fastcarb.fr/ 

17. Home | Endurcrete 

18. Recode - Project (recodeh2020.eu) 

19. ECO-Binder project - Home | Facebook 

20. Headline 2 (co2-utilization.net) 

SUSTAINABILITY/EMISSION REDUCTION 

• LC3 saves up to 40% of CO2 compared to OPC, while on a global scale the CO2 reduction is 1-2%. Furthermore, production costs are lower by 25% [11]. 

• EnDurCrete formulated cements contain only 47-53% clinker, the rest being replaced by high-quality SCMs that are valorised industrial by-product. This results in 45% reduced Global Warming Potential compared to OPC and saves non-renewable natural resources and energy [17]. 

NEW MATERIALS/EMISSION REDUCTION 

• Aether provides a 25%-30% reduction in CO2 emissions thanks to lowering the limestone content in the raw mix, decreasing the temperature (~1300°C) during the burning process and using less energy for grinding. Additionally, nitrogen oxide (NOx) emissions are lower than with OPC production [12]. 

• Solidia technology for concrete production could lead to a CO2 reduction of up to 70% compared to OPC and allows for 80% of the process water to be recycled [14]. 

CARBONATION/EMISSION REDUCTION 

• Fastcarb uses a reaction chamber in which exhaust gases from the kiln pass over crushed recycled concrete resulting in up to 50% CO2 capture within the concrete paste [2]. 

• RECODE proposes a reduction of at last 20% of process CO2 emissions from the production of SCMs nanofillers, whose CO2 footprint is neutral or even carbon negative [18]. 

EnDurCrete focuses on developing a new cost-effective sustainable reinforced concrete for durable and added value applications. The concept is based on the integration of novel low-clinker cement including high-value industrial by-products, new nano and micro technologies and hybrid systems ensuring enhanced durability of sustainable concrete structures with high mechanical properties, self-healing and self-monitoring capacities (Horizon 2020, 2018-2021). 

LC3 aims to make a standard and mainstream general-use cement in the global cement market. The new type of cement that is based on 50% clinker replacement level by a blend of limestone and calcined clay. LC3 can reduce the CO2 emissions by up to 40%, is made using limestone and low-grade clays which are available in abundant quantities, is cost effective and does not require capital intensive modifications to existing cement plants. (Swiss Agency for Development and Cooperation, 2014-present). 

ECO-binder aims to develop a new generation of concrete-based construction materials with more than 30% lower embodied energy, 20% improved insulation properties and 15% lower cost than the current solutions that are based on OPC. The main objective is to demonstrate that OPC can be fully replaced with new ones based on the Belite-Ye’elimite-Ferrite (BYF) class of low-CO2 binders, without compromising on quality or cost (Horizon 2020, 2015-2018). 

Aether aims to develop a new, innovative class of clinkers, with a lower environmental footprint. Less limestone is required to produce Aether cements, which are also manufactured at lower temperatures and using less energy than conventional OPC. This allows a 25-30% reduction in CO2 emissions during the production process (LIFE+, 2012). 

C2CA aims to develop three innovative technologies for recycling end-of-life concrete that yield fine cement paste, coarse aggregate and fine binding materials. C2CA also helped to create government mechanisms for recycling of concrete from old buildings to new ones (FP7, 2011-2015). 

CO2MIN focuses on identifying minerals suitable for permanently sequestrating CO2 from flue gas. The carbonised minerals produced using these technologies could be used for various product applications in the construction industry (Federal Ministry of Education and Research, Germany, 2017-2020). 

CO2WIN focuses on the areas of electrochemical conversion of CO2, chemical and biotechnological processes for the production of sustainable chemicals and fuels as well as mineralization using CO2 for the production of climate-friendly building materials. This technological diversity will be necessary for the industrial recycling of carbon to succeed in the future (Federal Ministry of Education and Research, Germany, 2020-2024). 

C²inCO2 key objective is to carbonate the recycled concrete fines (paste) using exhaust gases from the cement plant containing CO2. The carbonated hardened cement paste can be used as a clinker substitute, thus decreasing the clinker content in cement, preserving natural resources, and reducing CO2 emissions (Federal Ministry of Education and Research, Germany, 2020-2023). 

SOLID LIFE ( Solidia) project aims to demonstrate the feasibility of producing low-emission cement and concrete products on an industrial scale in existing industrial installations. The new products would have cost the same to make as the conventional Portland cement but have superior performance and reduce CO2 emissions by 70% (LIFE, 2016-2019). 

TRACK4REUSE addresses the challenge of optimising industrial truck traffic and introducing new standards for the green construction and demolition waste (CDW) industry, with the aim of reaching the EU goal of using 70 % recycled material. This will result in reduced construction environmental impact, improved traceability and recycling and increased onsite safety (Horizon 2020, 2020-2022). 

RE4 goal is to promote new technological solutions for the design and development of structural and non-structural pre-fabricated elements with high degree of recycled materials and reused structures from partial or total demolition of buildings (Horizon 2020, 2016-2020). 

RECODE promotes a circular-economy-approach by reusing the CO2 produced during the cement manufacturing within the plant itself to produce better SCMs entailing less embedded energy and related CO2 emissions (CaCO3 nanoparticles to be used as concrete fillers) (Horizon 2020, 2017-2022). 

FastCarb aims to combine concrete recycling and with its ability to capture CO2 in an accelerate way. This approach reduces the carbon footprint of concrete and promotes circularity (Institute for Applied Research and Experimentation in Civil Engineering, 2018-2022). 

SCOT focuses on how CO2 can be used in accelerated mineralisation to create low-carbon construction materials. Industrial wastes (low-value materials) can be converted into useful higher-value products for the building sector (synthetic aggregate). This provides means that can permanently sequester CO2, divert waste from landfill, avoid landfills costs and reduce the extraction of virgin aggregate materials (FP7-Regions 2013-2016). 

Carbon8 treats industrial residues from the steel, cement, pulp and energy sector (fly ashes) with CO2 captured directly from the source through accelerated carbonation to produce lightweight carbon-negative aggregates for various applications in construction. This represents an alternative to natural virgin aggregates, inherently reducing the carbon footprint of the concrete and reducing the consumption of primary raw materials, thus contributing to circularity (Carbon8 Systems Ltd. Company, UK, a spin-out from the University of Greenwich, London).