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  • Célestin Toeset

Circular Concrete - Solutions for a Global Transformation of the Built Environment



In 2018, the United Nations projected that a staggering 68% of the world's population will live in urban areas by 2050. As the need to accommodate larger societies grows and wealth increases across the globe, so does the demand for concrete. Perhaps the most distinctive mark of the Anthropocene, concrete is the predominant ingredient in the built environment. Last year, production levels of the resource amounted to 4.1 billion tonnes globally, close to triple the volume generated only thirty years prior. In parallel, global CO2 emissions linked to this practice have followed the same growth pattern. Now, the challenges that lie ahead - to limit global temperature increases to 1.5°C above pre-industrial levels and achieve net zero in the concrete industry by 2050 - require a considerable rethinking of existing processes. As global demand for concrete is projected to grow by 48% by 2050, we present multiple angles from which this issue can be approached.  


Revising concrete structures: innovations as drivers of change


Most efforts to reduce the industry's emissions target the conventionally used concrete blend. Its production involves several steps that produce significant CO2 emissions, particularly during cement manufacturing. First, raw materials like limestone and clay are heated in a kiln to produce clinker. The clinker is then ground into cement. This cement is mixed with water, sand, and gravel to form concrete. The mixture is poured into moulds and left to harden through curing at the construction site. Coming back to the emissions issue, it is estimated that for the production of 1kg of conventional concrete (using generic Portland cement), around 930 grams of CO2 are released into the atmosphere. Adjusted for the global production figure mentioned above, this would mean close to 3.81 billion tonnes of CO2 are emitted annually from concrete production alone. 


In recent years, various sustainable and circular alternatives have been researched and commercialised to shift away from traditional manufacturing processes. New concrete mixtures use alternative materials such as fly ash (a by-product of coal combustion), slag cement (a by-product of steel production), or recycled aggregates. They aim to reduce clinker-to-cement ratios, enhance durability, and avoid waste. New technology is also being integrated to reduce the industry's carbon footprint, presenting plastic waste, geopolymer concrete, and captured carbon as viable alternatives. Additionally, the reuse of construction site waste presents significant benefits, as materials can be repurposed or repaired rather than discarded, concrete debris can be crushed for use as a base in new projects, and steel and timber can be reclaimed for other building purposes. These innovations represent essential steps toward a more sustainable construction industry, promoting a circular economy and reducing the environmental impact of building activities. As part of Circular Innovation Lab's ambition to contribute to the growing body of sustainable alternatives, a number of these solutions will soon be available in the developing Global Circular Economy Innovation Database (GCEID). 



Widening the scope: considering the entirety of the value chain


While innovations often take centre stage when talking about a green transition in construction, the focus has also shifted to value chains in their entirety. Materials and aggregates no longer encompass the entirety of the playing field, which has been enlarged to include every stage of the value chain


While concrete is usually a locally produced material, companies have begun targeting transport and storage-related emissions. In 2022, for instance, the European Cement Association (CEMBUREAU), which serves as a representative organisation of the cement industry in Europe, published a position paper in support of this case. It notably mentions the development of a "pan-European CO2 transportation and storage network" for concrete-related emissions. This network would capture said emissions produced during clinker production (the most carbon-intensive stage) and transport them for safe storage in geological formations. This approach offers a promising solution for mitigating a significant portion of the industry's environmental footprint. However, crucial challenges remain. Building such a large-scale infrastructure project requires substantial investment and navigating complex regulatory hurdles across various European countries. Additionally, ensuring the long-term safety and effectiveness of these storage sites is essential to generating a lasting solution.


Beyond capture and storage, the roadmap also emphasises the importance of optimising logistics throughout the cement and concrete value chain. This includes exploring alternative modes of transport, such as inland waterways and rail, which typically have a lower carbon footprint compared to road freight. Additionally, optimising delivery routes and implementing just-in-time delivery schedules can further reduce transport-related emissions. By implementing a multifaceted approach that tackles emissions at every stage, from clinker production to concrete delivery, the construction industry can make significant strides towards a more sustainable future.


Addressing these challenges necessitates collaboration between industry leaders like CEMBUREAU, governments, and research institutions. Public funding initiatives and streamlined permitting processes can incentivise investment in CO2 capture and storage technologies. Furthermore, ongoing research and development are crucial for optimising storage techniques and ensuring the environmental integrity of these projects. 


Leveraging Artificial Intelligence (AI) as a tool for process improvement


It is a difficult task to overlook the impact AI will have on the construction sector in the coming years. Considering its wide range of applicability, the emerging technology is already being applied in industry operations worldwide. Whether it be to build in a more efficient way to minimise waste and promote efficiency or to automate project planning, AI serves as a valuable instrument. One key area of impact lies in optimising concrete mix design. Predictive AI algorithms can analyse datasets on material properties and environmental factors to create concrete formulations with lower embodied carbon footprints. This could involve identifying optimal combinations of alternative materials like those mentioned above or tailoring the mix design for specific project requirements, ultimately reducing the amount of material needed. AI is also transforming production efficiency. Predictive maintenance, powered by AI analysis of sensor data from clinker production plants, can anticipate equipment failures before they occur. This approach reduces downtime and the associated energy consumption. Looking ahead, AI-powered robots hold promise for minimising material waste during construction. These robots can be used for 3D printing of structures or automated bricklaying, ensuring precise material deposition and improved construction efficiency.


Beyond the construction site, AI contributes to sustainability through digital twins. These digital replicas of physical structures or processes allow for AI-powered simulations to optimise construction workflows before construction begins. By identifying potential sustainability bottlenecks early on, digital twins can lead to more efficient use of materials and reduced on-site waste generation.


The potential benefits of AI extend beyond just these initial examples. As technology continues to evolve, we can expect even more innovative applications that will significantly reduce the environmental impact of the construction sector. For instance, AI-powered logistics management systems can optimise delivery routes and schedules, minimising transportation-related emissions. It can further be used to streamline permitting processes and improve waste management practices, advancing the industry's environmental goals.


The successful integration of AI into construction requires collaboration between industry stakeholders. Construction companies, technology providers, and government agencies must work together to develop and implement solutions that address the industry's specific sustainability challenges whilst erring on the side of caution regarding AI's relatively unknown capabilities. Ongoing research and development will be crucial to ensure it is used effectively and responsibly throughout the construction lifecycle. By embracing AI and fostering a collaborative environment, it can be leveraged to aid the much-needed transition the industry is going through. 


Overall, the current path followed by the construction sector shows promise. While not necessarily on the desired course to meet 2050 targets yet, a number of tools can be utilised to steer the industry in the right direction. All levels of market actors are pushing the transition. Companies, entrepreneurs, and large-scale conglomerates are trying to get ahead of the curve by revising concrete mixtures by including alternative aggregates that have already been shown to decrease waste generation and carbon emissions. From an institutional angle, both governmental and non-governmental organisations have emphasised the necessity of a sustainable transition. Although highlighted in this op-ed, CEMBUREAU is only one of many advocates who propose guidelines to guide such a shift. Others have advocated the use of AI, which has shown remarkable potential when applied to construction practices, training, and project management. However, regardless of the angle from which we approach the issue, one thing is clear: there needs to be simultaneous engagement from all industry stakeholders. From AI and government policy to international standards and financing, a transition is only possible if a multifaceted approach is implemented. 


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