Building a better concrete
Thanks to its strength, durability, efficiency, safety and low carbon footprint, concrete has become the world’s construction material of choice. Unfortunately, because concrete infrastructure also includes embedded metals like steel that do corrode, the concrete itself is susceptible to cracking and deterioration – ultimately creating a safety risk. Recently, bacteria-based self-healing concrete has emerged as a promising solution to the concrete cracking conundrum. However, this technology’s market appeal is limited due to the general weakness and brittleness of the calcium carbonate it uses. With the support of EU funding, researchers from the Delft University of Technology and Cornell University have created Biocrete, the world’s first biologically inspired, bacteria-based, stress-responsive concrete. “Biocrete’s edge lies in its blend of bio-inspired material synthesis and cementitious materials design,” says Damian Palin, Biocrete project coordinator and Marie Skłodowska-Curie fellow. “The result is a concrete that offers superior crack healing action, better functional performance and increased durability.”
From seashells to cement
Inspired by the formation of seashells, researchers created Biocrete by controlling the calcite crystal (limestone) formation in anisotropic agarose gels. This resulted in the development of an agarose-calcite composite material offering various structure functionalities. Using an agarose film with a fibrous network, researchers were able to form calcite crystal composite discs oriented parallel to the fibres. In contrast, uniaxially deformed agarose gel cylinders resulted in rice grain-shaped crystals. “This exciting addition of direction-specific structure-functionality into crystal composites via appropriately designed gels could open the door to crystal composite materials with anisotropic structure-functional properties,” explains Palin. “Such a material would be particularly well suited for applications used in, for example, construction, photonics, and energy storage and conversion.”
Towards a resource-efficient cementitious material
By expanding our understanding of forming calcite crystal composite materials in polymer gel systems, the Biocrete project has laid the foundation for additional research into bio-inspired building and construction materials. “This work has added to our understanding of how nature forms her mineralised tissues,” remarks Palin. “It also provides a promising platform for rationally controlling bacteria-induced mineral precipitates for bacteria-based self-healing concrete applications.” To share this knowledge with the next generation of designers, Palin developed and taught a dedicated course at Ireland’s National College of Art and Design. Drawing from the project’s work, the course exposed students to bio-inspired theory and practice through a series of lectures, workshops and site visits. “The aim of this course was to encourage the uptake of bio-inspired design,” adds Palin. Palin is now continuing his research via a fellowship at Trinity College Dublin. Specifically, he is working to develop 3D-printed gel-based strategies for controlling the structure-properties of cementitious materials. “I am confident that this work will result in a resource-efficient cementitious material that can meet the same structural demands as current concretes while using radically less cement,” concludes Palin. “Such cementitious materials could be a key enabler in Europe reaching its sustainability goal of becoming climate-neutral by 2050.”
Keywords
Biocrete, concrete, cementitious material, cement, construction, infrastructure, building, composite materials, sustainability, climate-neutral
