The ingredients with organic qualities in concrete are sand, stone,
water and cement –which gives nutrition to Cladosporiums –black
The growth and the affections have started.
The affections are further even more when the concrete binds damp and dirt in the surface pores. The black moulds spores are very small and get an easy grip in the concretes fine surface.
As long as remains of black mould or spores remains in the surface pores the affections will recur, and therefore the surface must be disinfected. At the same time all growth are sterilized and can not keep on growing.