As we cautiously emerge from the coronavirus (COVID-19) lockdown, the UK Government is promoting infrastructure projects to help reboot the economy. Therefore, we can expect to see investment in and focus on the delivery of existing and new infrastructure projects. However, its important that these projects deliver a ‘green’ as well as economic recovery. They must conform to the legislation laid for achieving net-zero carbon emissions by 2050 and address the looming climate emergency.
Accelerated infrastructure delivery will increase demand for construction materials. Undoubtably, concrete will make up a high proportion of this demand. A key component of concrete is Portland cement (PC) clinker, the production of which is responsible for a sizeable chunk of anthropogenic carbon emissions. Industry is exploring ways to reduce this carbon burden by looking at alternatives to concrete. However, to ensure that carbon emissions are truly being reduced, product life cycle assessments (LCA) are needed to establish that impacts are not simply being shifted from, say, production to other life cycle stages.
Concrete Canvas® is one such alternative product. It is a Geosynthetic Cementitious Composite Mat (GCCM)– essentially, a fibre matrix that is impregnated with a dry concrete mix on a waterproof PVC backing. It is transported on a roll and can be installed with minimal equipment. Once it has been hydrated with water, it forms a concrete layer (see Figure 1). Concrete Canvas has many advantages over traditional concrete including:
- Can be laid at much lower thicknesses.
- Can be transported dry, which reduces freight burdens.
- Installation and removal is far simpler.
To quantify its potential environmental benefits, Concrete Canvas Ltd appointed Ricardo to undertake an LCA of its 8mm Concrete Canvas (CC8) product compared with traditional 150mm thick ST4 (20MPa) poured concrete.
Figure 1: Concrete Canvas being installed in two different projects
CC8 and ST4 can both be used to line channels. Consequently, Ricardo developed a spreadsheet-based tool that could compare both systems on a functional unit of 1m2 of channel. The tool enables the user to specify the dimensions of the desired channel; variables such as the distances between the project site, factories and end-of-life disposal; anticipated installation and removal times; the comparable GCCM thickness; and depth of ST4.
For the purposes of the study, Concrete Canvas Ltd specified a 500m channel with a width of 3.6m. The channel was located in Birmingham – 200km away from the company’s factory in Pontyclun. It was assumed ST4 would be sourced locally – 20km away. The study assessed each system’s global warming potential (GWP) – measured in kg of carbon dioxide equivalent per square metre (kg CO2e/m2) – considering a cradle-to-grave system boundary. This means it included all the upstream processes associated with raw material extraction; core (production) processes such as energy use during manufacture; and downstream processes such as installation, use, removal and disposal.
The results (see Figure 2) show that the CC8 system is hugely preferable to the ST4 system, having 55% of the total GWP value. CC8’s core (i.e. manufacturing) burden (green bar) is higher than that for ST4, but this is outweighed by its lower material, installation, removal and transport burdens.
The largest difference between the two systems was found to be due to the much higher mass of concrete needed in the ST4 system. The carbon emissions arising from this are largely linked to upstream processes and, perhaps unsurprisingly, driven by the manufacture of cement clinker. It is the difference in concrete mass required by the two systems that also results in higher transport burdens for ST4.
Figure 2: Graph of GWP results for the functional unit of 1m2 of the installed channel for the CC8 and ST4 systems
This is a great result for Concrete Canvas, but we didn’t want to just leave it at these initial results. Using our tool’s user interface, we changed the variables to model alternative scenarios, testing the sensitivity of the results to the assumptions. One such piece of sensitivity analysis was changing the required thickness of ST4 concrete to identify the ‘tipping point’ at which traditional concrete became preferable over CC8 (see Figure 3). The tool identified that the depth (or thickness) of ST4 must be reduced to 82mm to become preferable to CC8 – a 45% reduction in thickness. While this would result in a lower GWP, it is not practicable to install ST4 this thinly and steel reinforcements would be required, which would themselves contribute to GWP.
Figure 3: Graph of GWP results for the functional unit of 1m2 of the installed channel for the CC8 system and five different thickness scenarios for the ST4 system
This study provides Concrete Canvas Ltd with the evidence that its product is preferable to ST4 in terms of GWP. Furthermore, beyond these project-specific results, Ricardo’s tool will enable Concrete Canvas to enter the dimensions and variables specific to prospective clients and demonstrate what the impacts would be using its GCCM products or ST4 concrete for channel lining. The impacts are broken down by life cycle stage and step. This will demonstrate to clients the impacts that arise from increased vehicle movements on site or longer installation times, and will provide a comprehensive analysis that is specific to their needs.
Ricardo also carried out a range of other sensitivity analyses, looking into the type of cement used for each product and the time required to remove each system at the end of its working life. For both cases, CC8 was found to be preferable to ST4 concrete.
It’s been a great experience working with Ricardo on this project. Being able to robustly quantify the benefit our product offers over poured concrete is immensely useful to us. The new tool enables us to compare impacts that are specific to our clients’ projects. As infrastructure projects are brought forward, it’s really important that projects have access to the information they need to select low-carbon solutions, such as our Concrete Canvas GCCM products.
Lee Church, Technical Manager, Concrete Canvas Ltd
When considering the environmental impacts of a product, it is important to look beyond purely the manufacture stage, and to consider other life cycle stages and the effects of potential variables upon a system.
If you are interested in assessing the impact of your product, please get in touch. You can also read about Ricardo’s wider LCA capabilities here, or read our other LCA blogs on Environmental Product Declarations (EPD) and assessing the GWP of a steak dinner.
For more information on Concrete Canvas, you can visit their website.