Deconstructing Construction: The Role of Limestone Fines in Low-Carbon Concrete

Introduction

In the ever-evolving world of construction, sustainability and environmental consciousness have become pivotal considerations. Concrete, a fundamental building material, has recently undergone a transformative shift with the revision of the BS 8500 concrete standard by the British Standards Institution (BSI) after a comprehensive two-year testing period. This revision introduces powdered limestone as a third component, alongside traditional additives like fly ash and ground granulated blast furnace slag (GGBS). This article delves into the implications of the new standard, focusing on limestone fines and their role in low-carbon concrete.

Changes to the Traditional Concrete 'Recipe'

The BS 8500 revision marks a significant departure from the traditional concrete 'recipe' and opens the door to more lower-carbon options. Previously, CEM I, combined with either fly ash or GGBS, was the norm. Now, with the inclusion of powdered limestone, the construction industry gains an additional sustainable alternative. This shift is crucial for reducing the embodied carbon of concrete, offering a new frontier for specifiers and engineers committed to decarbonizing construction practices.

Understanding Limestone Fines

Limestone fines are finely ground limestone sourced from UK quarries, readily available and abundant. Elaine Toogood from The Concrete Centre highlights that limestone fines provide a sustainable alternative to traditional additives, essential for lowering the embodied emissions of concrete. This is particularly significant as the availability of fly ash and GGBS diminishes due to the reduction in coal-fired power and the ongoing decarbonization of the steel industry.

Performance of Concrete with Limestone Fines

Extensive testing, part of a rigorous two-year research and testing process, has demonstrated that concrete containing powdered limestone maintains high strength, durability, and fire protection comparable to CEM I concrete. The BSI technical committee for concrete independently assessed these results, providing confidence in the viability of the new standard. This reassures construction professionals that the integration of limestone fines does not compromise the structural integrity or performance of the concrete.

Environmental Impact and Carbon Reduction

The adoption of the new cement types could potentially save approximately 1 million tonnes of CO2 emissions annually across all UK construction sites. This substantial reduction is equivalent to over 3,500 transatlantic flights. Moreover, incorporating limestone fines into concrete can yield a proportional decrease in CO2 emissions. For every 5% of limestone powder used, a 5% reduction in CO2 emissions per cubic meter of concrete can be achieved. The maximum replacement of 20% limestone offers a significant 20% carbon saving. This presents a unique opportunity for clients, consultants, and contractors to contribute to carbon reduction goals while utilizing responsibly manufactured materials sourced within the UK.

Examples of Implementation

The successful trial of the new lower-carbon concrete mixes at the £6.5 million Hexham flood alleviation scheme in Northumberland stands as a testament to the viability of limestone powder. In this trial, three concrete panels totaling 27 meters showcased an impressive carbon saving of 64% compared to CEM I concrete. This real-world application demonstrates the feasibility and effectiveness of incorporating limestone fines into concrete construction projects.

Industry-Wide Commitment to Decarbonization

The revision of the BS 8500 concrete standard is just one facet of the UK concrete and cement industry's commitment to reducing carbon emissions. The industry's roadmap outlines various strategies, including decarbonized transport, fuel switching, and the adoption of Carbon Capture, Usage, or Storage (CCUS) technology. Remarkably, the industry has already achieved a 53% reduction in absolute carbon emissions since 1990, outpacing the overall decarbonization rate of the UK economy.

Conclusion

The integration of limestone fines into the BS 8500 concrete standard is a pivotal moment for the construction industry. It not only expands the array of lower-carbon options but also addresses the diminishing availability of traditional additives like fly ash and GGBS. The environmental and carbon reduction benefits, coupled with successful trials such as the Hexham flood alleviation scheme, underscore the potential of this innovation. As the UK concrete and cement industry continues to make strides in decarbonization, the revised standard stands as a beacon of progress, offering a concrete solution to the construction sector's sustainability challenges. It is incumbent upon construction managers, specifiers, engineers, and suppliers to embrace this shift, engage early in the process, and collectively contribute to a more sustainable and environmentally conscious future for construction.

Call to Action

Are you an investor or developer with a commercial real estate or infrastructure project? It's time to explore the game-changing potential of our information management process. This takes the project sponsor from inception to successful operations by looking in detail at the end game at the very beginning using an adapted RIBA plan of work.

Get in contact by emailing [email protected]

Author

Ian J. Rogers

With a track record of delivering successful projects, I offer consultancy services that drive a project’s success. I also can provide training, coaching and mentoring.

I am your experienced guide (sherpa) helping you navigate the complex world of information management and project processes and I will provide solutions that improve your project, increase profitability, and minimize risk.

I have worked with or on medium to large projects as a Quantity Surveyor, Project Manager and Facilities Manager.  I also have experience of structured finance. So I can truly look at the whole life cycle of a project.

My consultancy services, offered in-person, remotely, and in a hybrid format, are founded on aligning projects for success.

Don't just take my word for it - my clients speak to my expertise and approach.

Accreditations

BSc Quantity Surveying

Member of the Royal institution of Chartered Surveyors

Member of the Institute of Workplace and Facilities Management

Member of the International Facility Management Association