Abstract:
In this paper, the complexities involved in both microbiologically influenced
corrosion and deterioration of reinforced concrete structures by algae are explained. In this
regards, the five possible corrosion/deterioration mechanisms that may be expected are
addressed and described. These mechanisms are as follows:
• Absorption of some chemicals necessary for the algae from within the cement
paste of the concrete: this mechanism can finally result in drying out the concrete
and developing cracks as a result of formation of internal cavities and voids.
• Biofilm formation and increasing the likelihood of attracting more micro-/macroorganisms
that can either deteriorate the concrete itself or the reinforcement steel
inside , or both. An example as such can be development of an environment
favorable for the acid-producing sulphur oxidizing bacteria that through
generating very acidic conditions are capable of doing harm to both metallic and
non-metallic phases of the reinforced concrete.
• Development of electrochemical cells such as differential aeration cells due to the
photosynthetic driven oxygen production and consumption features of algae. In
On the Impact of Algae on Accelerating the Biodeterioration/Biocorrosion of Reinforced
Concrete: A Mechanistic Review 395
this way, it is likely that spots of varying oxygen partial pressures will be created,
tus facilitating the corrosion of the steel inside.
• Production of acids that can be detrimental to the mechanical integrity of both
concrete and steel reinforcement.
• Production of alkaline conditions that upon varying and fluctuating due to the
chemistry of the system, can protect the concrete but do damage to the steel phase
via mechanisms such as caustic embrittlement.
The aim of this review paper is to gather all possible mechanisms that may be
involved in explaining the contribution of algae to the bio-corrosion/bio-deterioration of reinforced concrete.
