Credit: FEFU press office Preparing regular concrete scientists replaced ordinary water with water concentrate of bacteria Bacillus cohnii, which survived in the pores of cement stone. The cured concrete was tested for compression until it cracked, then researchers observed how the bacteria fixed the gaps restoring the strength of the concrete. The engineers of the Polytechnic Institute of Far Eastern Federal University (FEFU), together with colleagues from Russia, India, and Saudi Arabia, reported the results in Sustainability journal. During the experiment, bacteria activated when gained access to oxygen and moisture, which occurred after the concrete cracked under the pressure of the setup. The "awakened" bacteria completely repaired fissures with a width of 0.2 to 0.6 mm within 28 days. That is due to microorganisms released a calcium carbonate (CaCO3), a product of their life that crystallized under the influence of moisture. After 28 days of self-healing experimental concrete slabs retrieved their original compressive strength. In the renewed concrete, the bacteria "fell asleep" again.