Investigating the effect of adding bacillus bacteria and nano-clay on cement mortar properties

Bacterial deposition is one of the techniques recently used to repair and improve concrete properties. Biological mortar is a mixture of bacteria, aggregates, cement, and a nutrient medium containing calcium salt. These bacteria created bounds in the concrete materials by producing microbiological calcium carbonate. In this study, the effect of biological healing was investigated on the properties of concrete mortars containing nano-clay. For this purpose, the effect of healing by bacillus bacteria on untreated mortar specimens was compared with those containing nano-clay. The specimens were then examined through scanning electron microscopy (SEM), weight gain, permeability, sulfate attack, carbonation, and compressive strength (UCS) tests. The results showed that the bacterial deposition rate increased in specimens containing nano-clay compared to untreated specimens. Also, the permeability rate in the nano-clay-treated specimens in the short term was higher than in untreated specimens; however, in the long term, it was lower than that of the untreated specimens. After coating, specimens containing nano-clay and untreated specimens had better performance against sulfate attack than non-coated untreated specimens. Also, the resistance of mortar in these specimens to this damage increased by 15.2 % and 9.2 %, respectively. Additionally, like sulfate attack, resistance to carbonation in the coated nano-clay treated and untreated specimens increased compared to non-coated untreated specimens by 34 % and 15.9 %, respectively. The UCS of the specimens was investigated in four cases: un-treated (control) specimens experienced a 4.3 % reduction in resistance compared to the speci-mens created by adding nano-clay to the mortar specimen. The strength was increased by 6.7 % in untreated specimens after coating. Finally, the strength increased by 13.5 % in the coasted specimen containing nano-clay.