Definition - What does Cement Bacillus mean?
Cement bacillus is an older term for ettringite, a mineral high in sulfate calcium sulfoaluminate. It occurs naturally or is formed by sulfate attack on mortar and concrete. Bacillus is bacteria which increases the compression strength of concrete through their biomass.
The disintegration of concrete in seawater and sulfate solutions is due to the formation of cement bacillus. It is the main reaction product formed by the expanding form of sulfate attack.
Corrosionpedia explains Cement Bacillus
Cement bacillus is also known as ettringite, which is the name of a naturally occurring mineral of the same composition and structure. The formation of cement bacillus has been recognized as the cause of excessive expansion, cracking and even complete disintegration of concrete subjected to intensive sulfate attack.
Cement bacillus has advantages and disadvantages, depending on the circumstances and conditions in which it forms. It is a product of reaction between sulfate and calcium aluminate. It is an expansive compound, and is bigger in volume (is of smaller density) than its forming chemicals.
However, when ettringite is formed in an already hardened cementitious system, the tensile stresses it creates lead to expansion of the system as a whole, and this results in cracks that, at times, ultimately lead to total collapses.