Autogenous healing is the natural process of crack repair that can occur in concrete in the presence of moisture, and the absence of tensile stress. The repair is by a combination of mechanical blocking by particles carried into the crack with the water and the deposition of calcium carbonate from the cementitious material.
Autogenous healing has practical applications for closing dormant cracks in a moist environment, such as may be found in mass structures and in water retaining or watertight structures. Both BS 8007, The design of concrete structures for retaining aqueous liquids, and the water Services Associationís Specification imply that cracks up to 0.2 mm wide will autogenously seal within 28 days; cracks up to 0.1 mm will seal within 14 days.
Further information may be found in Concrete Advice No. 09, Autogenous healing: self sealing of fine cracks.