Saving Carbon

09 August, 2022

First published in the August 2022 issue of Quarry Management

Five steps the UK construction sector can take now

By Dr David Rich, sustainability performance and compliance manager, Tarmac

When we talk about the net-zero transition, it is tempting to think of it as tomorrow’s issue and as something we can gradually work towards. But with 42% of UK greenhouse gas (GHG) emissions derived from the built environment, the stark reality is that construction needs to make significant changes to reduce emissions across the development life cycle.

The task of deeper decarbonization for all industries gets harder and more complex as we progress, but there are already practical, behavioural, and technological changes that can help clients, contractors, and design teams to save carbon now. The following are five steps for material specification that can deliver significant carbon savings.

Engage as early as possible with materials suppliers

While there are some excellent examples of infrastructure clients developing integrated and collaborative supply chains, there is also greater scope to make early engagement of materials partners the norm across all parts of the market.

Clients, contractors, and specifiers who engage with construction products manufacturers early in the design process can benefit from a wealth of information and guidance to help them make better-informed decisions about their choices of materials.

This also means that suppliers can consider the most sustainable logistics and provide a carbon footprint assessment up front. By considering how to reduce CO2 at the start of the project, rather than as an afterthought, carbon cutting can be a much more efficient process.

Optimize material mixes

For materials such as concrete, early engagement provides an opportunity to optimize mixes in order to deliver carbon savings.

For example, low-carbon concrete design is already available and proven. Today, as standard, it is possible to achieve up to a 70% reduction in the embodied carbon of concrete compared with CEM I.

There are also plenty of other ways to decarbonize a concrete structure through design and specification, including span, loading and structural systems. The key to decarbonizing concrete at a project level is to assess the possible options early on.

End traditionalism and utilize low-carbon technology

We are now at a stage where a range of low-carbon technologies are available, often with no difference in performance compared with traditional methods. But sometimes these materials are not understood.

Warm-mix asphalt for highways is a case in point. There are many projects now benefiting from this technology but in some parts of the industry there may still be a lack of understanding about the benefits of this material compared with traditional hot-rolled asphalt (HRA). Misconception, traditionalism, and the need for technical departure from standards can stifle the opportunity to deliver improved environmental and social outcomes.

Extend time scales to deliver low-carbon benefits

Where ‘slow travel’ and using trains instead of planes is the low-carbon solution for the travel industry, perhaps similar principles could apply for construction. Currently, concrete is strength tested 28 days after pouring. If we instead tested the strength of structures after 56 days, this would allow more time for the concrete to cure and gain strength, meaning less cement is needed in the mix.

The Mineral Products Association (MPA) has demonstrated this as an extremely simple way of reducing cement and therefore the embodied carbon of a project, at the cost of just a few weeks. Allowing longer setting times before strength testing means cement content can be reduced by 15–20kg/m3, which leads to a reduction of 5–10kg/m3 in CO2 emissions.

Avoid overspecification

The safety and durability of buildings and infrastructure are, of course, paramount, but a fear of technical failure has, over the last decade, led to unnecessary overspecification of materials for some structures. This comes with high carbon costs.

Today there is a wide range of modern concrete mixes and construction methods that can be more sustainable, based on the decisions of specifiers and contractors. These can ensure efficient structural design, without any negative impacts on strength or resilience.

The journey to net zero requires practical, behavioural, and technological changes. Some of these steps can be achieved today, so it is imperative that we collectively seize the opportunity.