Researchers look to nature for blueprints for stronger, more durable concrete

Researchers at MIT hope to redesign concrete by following nature’s blueprints. From their observations of strong, durable natural structures such as bones, shells and deep-sea sponges, the team has proposed a ‘bottom-up’ approach for designing cement paste, the binding ingredient in concrete, which requires a huge amount of energy to manufacture.

“These materials are assembled in a fascinating fashion, with simple constituents arranging in complex geometric configurations that are beautiful to observe,” said Oral Buyukozturk, a professor in MIT’s Department of Civil and Environmental Engineering (CEE). “We want to see what kinds of micromechanisms exist within them that provide such superior properties, and how we can adopt a similar building-block-based approach for concrete.”

Concrete’s strength and durability depends partly on its internal structure and configuration of pores: The more porous the material, the more vulnerable it is to cracking. However, there are no techniques available to precisely control concrete’s internal structure and overall properties.

“We’re dealing with molecules on the one hand, and building a structure that’s on the order of kilometres in length on the other,” Buyukozturk said. “How do we connect the information we develop at the very small scale, to the information at the large scale? This is the riddle.”

To start to understand this connection, he and his colleagues looked to biological materials and compared their structures and behaviour, at the nano-, micro-, and macroscales, with that of cement paste.

Through this research they found that a deep sea sponge’s onion-like structure of silica layers provides a mechanism for preventing cracks. Nacre has a “brick-and-mortar” arrangement of minerals that generates a strong bond between the mineral layers, making the material extremely tough.

Applying the information they learned from investigating biological materials, as well as knowledge gathered on existing cement paste design tools, the team developed a general, bioinspired framework, or methodology, for engineers to design cement, “from the bottom up”.

The framework is essentially a set of guidelines that engineers can follow, in order to determine how certain additives or ingredients of interest will impact cement’s overall strength and durability. Engineers could then plug these measurements into models that simulate concrete’s long-term evolution. These simulations can then be validated with conventional compression and nanoindentation experiments, to test actual samples of bioinspired concrete.

“The merger of theory, computation, new synthesis, and characterisation methods have enabled a paradigm shift that will likely change the way we produce this ubiquitous material, forever,” added Markus Buehler, CEE department head. “It could lead to more durable roads, bridges, structures, reduce the carbon and energy footprint, and even enable us to sequester carbon dioxide as the material is made.”

Author
Tom Austin-Morgan

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