By Dr David Rich, sustainability performance and compliance manager, Tarmac
When we talk about the net zero transition, it’s tempting to think of it as tomorrow’s issue and as something we can gradually work towards.
With 42 per cent of UK greenhouse gas (GHG) emissions derived from the built environment, the stark reality is that construction needs to make significant changes to lower emissions across the development lifecycle.
The task of deeper decarbonisation 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.
Here are five steps for material specification that can deliver significant carbon savings:
1. 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 lower CO2 at the start of the project, rather than as an afterthought, carbon cutting can be a much more efficient process.
2. Optimise material mixes
For materials such as concrete, early engagement provides an opportunity to optimise mixes in order to deliver carbon savings.
For example, low carbon concrete design is already available and proven. In fact, today as standard, we can achieve up to a 70 per cent reduction in the embodied carbon of concrete compared to CEM I.
There are also plenty of other ways to decarbonise a concrete structure through design and specification including span, loading and structural systems. The key to decarbonising concrete at a project level is to assess the possible options early on.
3. End traditionalism and make use of low-carbon technology
We’re now at a stage where we have a range of low carbon technologies available, often with no difference in performance compared to 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 to 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.
4. Extend timescales 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, we strength test concrete 28 days after pouring. If we instead tested the strength of structures after 56 days, this allows 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 and which leads to a reduction of 5-10 kg/m3 in CO2 emissions.
5. Let’s avoid overspecification
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.
As before, today there is a wide range 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’s imperative that we collectively seize the opportunity.