Image of the Day: Living Concrete

Bacteria and sand form a strong building material.

Emily Makowski
Jan 16, 2020

ABOVE: Building material made from cyanobacteria and sand

Bacteria and sand can be combined to form a living material that acts like concrete, according to a study published in Matter yesterday (January 15). Researchers led by Wil Srubar, a civil engineer and head of the Living Materials Laboratory at the University of Colorado Boulder, combined sand and hydrogel, an absorbent network of polymers, to form a scaffold. Then they added a species of Synechococcus, a photosynthetic cyanobacteria. The hydrogel provided moisture and nutrients for the bacteria, allowing them to grow and mineralize. The end result was a substance similar in strength to concrete-based mortar.

In this material, the bacteria remained alive and could reproduce. When the researchers cut a brick in half, it grew into two complete bricks with the addition of a bit of sand, hydrogel, and nutrients. However, it had to be kept at or above 50 percent relative humidity so that the bacteria didn’t dry out and die. Despite this limitation, the material is a starting point for making more eco-friendly building materials. Cement, used to make concrete, is responsible for 6 percent of carbon dioxide emissions, and concrete also releases CO2, according to a press release.

“What we’re really excited about is that this challenges the conventional ways in which we manufacture structural building materials,” says Srubar in the press release. “This is a material platform that sets the stage for brand new exciting materials that can be engineered to interact and respond to their environments.”

The material can be molded into different shapes.

C.M. Heveran et al., “Biomineralization and successive regeneration of engineered living building materials,” Matter, doi:10.1016/j.matt.2019.11.016, 2020. 

Emily Makowski is an intern at The Scientist. Email her at

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