12-01 3D print recycled concrete

[Image above] A new £6 million project led by Manchester Metropolitan University and partners across Europe looks to recycle waste concrete using additive manufacturing. They plan to showcase the potential of the technique by producing five urban, memorial, and garden furniture pieces. Credit: Manchester Metropolitan University

In recent years, the public has turned an increasingly critical eye on the cement industry for its role in greenhouse gas emissions. In turn, the cement industry is actively working to address these emissions in various ways, from replacing emission-heavy steps of the fabrication process with alternative techniques to developing industrial-scale carbon capture systems.

Yet carbon dioxide is not the only environmental impact of cement production, despite it being the most well-known. Another significant impact is the effect on global sand supply.

Humans currently use some 40–50 billion tonnes of sand and gravel each year, with those estimates based largely on activity in the cement industry. In addition to other applications of sand and marine extractions that are not included in those estimates, “it’s safe to say these activities add up to a lot of sand—much more than 50 billion tonnes per year,” we wrote in a CTT post this July.

Such high levels of sand extraction are unsustainable, both because of the limits on raw sand supply and also the negative impacts on the environment. Instead of extracting more raw material, one possibility for the cement industry is to take a page from the glass industry’s playbook and recycle.

“In developed countries, where new construction often replaces demolished buildings, there is untapped potential to recycle building rubble instead of using new concrete,” a Yale Environment 360 article says.

To date, recycling of building rubble is limited because the materials that make up rubble are quite varied, so the rubble does not meet strict building regulations. Additionally, the rubble can become contaminated during the demolition process, making it difficult to reuse.

A new £6 million project called CIRMAP led by Manchester Metropolitan University and partners across Europe aims to overcome these limitations using additive manufacturing.

Compared to traditionally manufactured products, “3D printed products are not subject to the same building restrictions, which is why they could provide a solution for the reuse of [recycled fine aggregates],” a Manchester Metropolitan University press release explains.

Researchers involved in CIRMAP have two main goals: to provide a new mixture proportioning method for the design of 3D-printed mortars with recycled fine aggregates, and to develop a new design methodology for customized shapes, which will be transferred to manufacturers.

The project will be based at Manchester Metropolitan University’s 3D additive and digital manufacturing hub, PrintCity. Between now and summer 2023, the researchers plan to showcase the potential of this technique by producing five urban, memorial, and garden furniture pieces that will be placed in the Greater Manchester area.

The researchers hope long-term impacts of the project will include up to 25 million tonnes of recycled fine aggregates being reused into 3D-printed products, and that “CIRMAP will not only benefit the North West of England, but also Europe and beyond,” Craig Banks, Manchester Metropolitan academic lead for CIRMAP, says in the press release.

If you are interested in working with the project partners, you can contact project manager Sheryl Lee at sheryl.lee@mmu.ac.uk.