Construction vs Plastics: The Importance of Material Innovation

April 22nd is Earth Day, and this year's theme is "Planet vs Plastic"; a fitting reminder of the plastic waste that is harming our planet.

Although plastic waste is a global issue, in the UK alone, the construction sector produces 35,000 tonnes of plastic packaging waste each year - equivalent to enough stretch wrap to circle the earth's circumference over 170 times. Moreover, about 50,000 tonnes of plastic waste is generated annually in the construction industry, with 40% of this amount being sent to landfill sites.

Recognising the urgency of the issue, SPACE Architect Catherine Sinclair undertook a research project to explore the untapped potential of post-consumer Polyethylene Terephthalate (PET) mesh in concrete bricks. By integrating post-consumer PET into concrete, Sinclair aimed to address two pressing challenges simultaneously: plastic pollution and the environmental impact of construction materials. In this article, we cover her resulting research, with a focus on mitigating plastic waste and enhancing the structural integrity of construction materials in a more environmentally friendly way.

The premise of Sinclair's work was to leverage the unique properties of PET mesh to reinforce concrete bricks. While the use of plastic as a replacement for both the coarse and fine aggregate has begun to be widely researched, Catherine's investigation of the use of post-consumer PET mesh in a concrete brick was the first of its kind to be carried out within the UK. 

One of Catherine's primary motivations for her study into PET mesh was the fact that plastic remains one of the most wasted materials. She also believes that the current recycling system needs to become more efficient in order to have a greater and more widespread impact.

For traditional concrete, which suffers from low tensile strength in comparison to compressive strength, the incorporation of PET mesh offered a promising solution. During her study, Sinclair carried out ten batches of concrete bricks, each embedded with varying amounts and placements of PET mesh. Catherine's efforts hoped that the recycled plastic mesh would improve the strength-to-mass ratio, meaning the amount of embodied carbon in the product would also be reduced. 

Through meticulous experimentation and testing, Catherine discovered that by adding one piece of PET mesh in a certain placement, the tensile strength of the brick increased. The brick with the highest tensile splitting strength had a strength of 2.526 Newtons/mm², which is a significant increase compared to concrete alone. Catherine's approach, therefore, not only utilises waste plastic but also improves the environmental impact per functional unit of a concrete brick. By improving the tensile strength of concrete with this specific type of plastic mesh, the mass of the brick barely changes, and therefore, the carbon produced in the transportation of the bricks remains the same.

Reflecting on her work, Sinclair remarked, "When I began my research, I was convinced that waste plastic could be used more efficiently within the construction industry to help tackle the plastic waste problem. Now, having completed my study, I am even more convinced of this fact. By reducing the use of other materials that have a detrimental effect on the environment and by further refining and testing post-consumer PET mesh, we can make it a fundamental material in construction."

By embracing innovation, Catherine's research sets the stage for future advancements and offers a practical pathway towards the adoption of greener construction practices. As we celebrate Earth Day and reflect on our collective responsibility towards the planet, Sinclair's work serves as a reminder of the important role innovation plays in paving the way towards a more sustainable built environment.