Prevention of Corrosion in Reinforced Cement Concrete (RCC) by Bacteria
Prepared By MD. Rakib Hossain and MD. Shaharul Islam
Department of Civil Engineering, Bangladesh University of Engineering and Technology.
Introduction 2Fe(OH)3 > Fe2O3.H2O+2H2O [Hydrated Ferric Oxide or Rust] Prevention of corrosion
There is a relative percentage for what corrosion of RCC is occurred
Steel gets oxidized (corrosion) in the present of oxygen and water.
is as follows:
Bio Concrete:
Even present of oxygen in the concrete pore will not cause a corro- The bacteria and Ca(OH)2 of pH 13 is added to the concrete
sion at high alkaline environment. Concrete contains microscopic
Bacteria are Bacillus Alkali-nitrulicus, Psychrophilic Bacterium,
pores which contain high concentrations of soluble calcium, sodium
Bacillus Pasteurii .
and potassium oxides, this creates alkaline condition of pH 1213.
The alkaline condition leads to a passive layer forming on the steel Survive at high pH of 9 to 13 and at the temperature range of 10 to
surface. The dense passive layer over the reinforcement prevents the 40 degree centigrade.
alkalinity. This poster involves in the prevention of corrosion by Bacteria get active with water and Ca(OH)2 with CO2
maintaining alkalinity in concrete by using bacteria. CO2 + Ca(OH)2 -> CaCO3 + H2O
Figure: Relative Volume of Iron (Fe) and its oxide from Mansfield Corrosion,1981,37
Corrosion process (5): 301-307 Diffusion of CO2:
Anhydrate Fe2O3 has a volume of about twice that of the steel. Diffusion is mass transport down a concentration gradient. Steady
When the passive layer breaks down then rust will start appearing on
the steel surface. When steel in concrete corrodes it dissolves in the When it becomes hydrated it swells even more and becomes po- state diffusion follows Ficks first law
pore water and gives up electrons: rous.
The anodic reaction is: Fe (s) > Fe
2+
(aq)+ 2e Increase volume at the steel or concrete interface is six to ten
The two electrons (2e) created in the anodic reaction must be con- times .
sumed elsewhere on the steel surface to preserve electrical neutrality. Leads to the cracking and Spalling as shown in figure below;
The cathodic reaction is: H2O +0.5O2 +2e >2OH Water cement ratio to reduce D :
The ion dissolve in the pore water. spalling of the concrete. w/c ratio =0.38
Several more stages must occur for rust to form. Using admixtures
Ferrous hydroxide becomes ferric hydroxide and then hydrated fer- 23% bound water
ric oxide or rust.
Using plasticizer for workability
Cause spalling and crack over the concrete.
Plasticizer increases the strength
up to optimum level above that
Figure: Schematic of corrosion induced spalling at corners and delamination at the it decreases the strength.
plane of the reinforcement.
Conclusion:
Carbonation: Carbonation is the result of the interaction of carbon
Even through, we had a good design, material and scheduling it is impossible to
dioxide gas in the atmosphere with the alkaline hydroxides in the attain strength and durability without good workman ship. For an example Ma-
concrete. san will add water in mortar and shovel it. For any RCC structure, corrosion is a
great threat to its durability and serviceability. To ensure proper durability for
Figure: Anode and Cathode Reaction of Corroding Bar
which it has been built, we need to ensure prevention of corrosion and using
2+
Now lets see the reaction of Fe and OH formed in anode and cath- bacteria in concrete is one of the solution to protect RCC from corrosion with-
ode combined to form ferrous hydroxide and further undergoes out affecting its strength.
chemical reaction as below: References:
1) John P. Broomfield; Corrosion of Steel in Concrete Understanding, investigation and repair, Taylor & Francis 270 Madison Ave,New York,NY 10016.
2+
Fe (aq) +2OH > Fe(OH)2 [ Ferrous Hydroxide] 2) M.S. Shetty; concrete technology theory and practices, S.Chandra and company ltd, Ram nagar , new Delhi.
3) IS10262-2007 Recommended Guidelines for Concrete Mix Design, Bureau of Indian Standards, New Delhi, 2007.4)en.wikipedia.org/wiki/Corrosion
5)https://www.google.com/search?q=prevention-of-corrosion-in-rcc-by-bacteria.html&sourceid=chrome&ie=UTF-8 .6)http://www.engineeringcivil.com/
4Fe(OH)2+O2+2H2O > 4Fe(OH)3 [ Ferric Hydroxide] Figure: Reaction of Carbonation Figure: Quantity of Rust(%) Versus pH graph 7) Bjrn Lagerblad Carbon dioxide uptake during concrete life cycle State of the art, ISBN 91-976070-0-2, ISSN 0346-8240.
8) Ravindranatha, N. Kannan, Likhit M, Self-healing material bacterial concrete,IJRET: International Journal of Research in Engineering and Technology, eISSN: 2319-1163 | pISSN: 2321-
7308.
