Developing Smarter Concrete with Biomaterials

By looking at the microscopic structure of biomaterials and its influence on macroscopic mechanical properties, researchers wish to apply a similar “bottom-up” design approach for developing better concrete. (Image courtesy of MIT.)

What is the most widely used man-made material on earth? Which material is single handily responsible for majority of the critical infrastructure that modern human societies require to function and thrive?

If you guessed concrete, then you are absolutely correct. Concrete consumption is estimated to be more than twice all other building materials combined!

Yet despite being a millennia-old product, concrete technology still has a lot of room for growth in terms of strength and sustainability.

In an exciting recent development, researchers look to take cues from biomaterials like bones, shells and deep sea sponges in using a “bottom-up” approach to redesigning concrete. Taking inspiration from nature in this manner is referred to as “biomimicry”.

MIT based researchers contrasted the molecular structure and properties of the biomaterials with cement paste (the binding agent of concrete), noting the remarkable strength and durability these biomaterials have. This is thought to be a consequence of the biomaterials having a precise and sophisticated assembly of structures at multiple length scales (from microscopic to macroscopic)

Based on these observations, Oral Buyukozturk, a professor in MIT’s Department of Civil and Environmental Engineering (CEE) proposed a “bottom-up” approach in designing cement paste by starting with the microscopic structures formed and observing their influences on macroscopic properties.

The researchers are looking at what kind of micro mechanisms exist within the biomaterials that provide them their superior properties and how this building-block approach can be applied to concrete. The ultimate objective of the researchers is to identify natural materials that may be used as alternatives to Portland cement in order to increase sustainability and durability of concrete.

Concrete at the Mesoscale

Concrete is an amalgamation of coarse and fine aggregates and additives such as admixes and cement paste which is more or less random. Researchers want to change the guesswork practise of concrete production by developing techniques to control the material at the mesoscale. The mesoscale describes the connection between microscopic structures and their macroscopic properties. This looks at how the microscopic arrangement within cement can effect the strength and durability of buildings, bridges and other structures.

Comparison of natural materials and cement paste showing the steps by which smaller pieces assemble to form larger structures. (Image courtesy of MIT.)

To understand this connection, the researchers looked at biomaterials such as the deep sea sponge’s onion-like structure of silica layers, which leads to a mechanism for preventing cracks. By synthesizing the information from investigating biomaterials and existing cement paste design tools, the research team developed a general bioinspired methodology for engineers to design cement from the bottom-up. This framework would function as a guideline that engineers can use to determine how certain ingredients will impact the cement’s overall strength and durability.

Buyukozturk is also looking into volcanic ash as a cement additive (a technique first discovered in ancient Rome) and engineers could follow this proposed framework in studying volcanic ash addition by first utilizing existing experimental techniques including X-ray diffraction, nuclear magnetic resonance and scanning electron microscopy to identify the evolution of volcanic ash’s solid and pore configurations.

Researchers could then use this data to simulate the concrete’s long term evolution, with an emphasis on understanding the mesoscale relationship between the properties of the ash and its contribution to the strength and durability of an ash-mix concrete-based piece of infrastructure. These simulations could then be validated by conventional tests on samples of volcanic ash-based concrete.

Concrete consumption is only expected to continue to rise as developing countries around the world undergo urbanization and have an increased demand for new infrastructure. To give some example of how much we are consuming as a species, China used more concrete for building projects between 2011-2013 than the US did in the entire 20^th century!

Advances in more efficient concrete through this approach could lead to more durable infrastructure and also reduce the carbon and energy footprint associated. The proposed framework by the researchers could help in developing concrete infrastructure that could have an extended design life at lower resource consumption.

For more information on the research paper published proposing this idea, visit the journal Construction and Building Materials. Also see an article discussing the similar idea of using biomimetics in developing stronger Calcite.