Chamber installation for concrete biocorrosion studies
V.I. Sigaev, K.G. Soloviev, R.V. Borovick, N.R. Dyadishchev, A.N. Varfolomeev, A.D. Tolchinsky, V.V. Kharlamov
State Federal Enterprise for Science “Research Center for Toxicology and Hygienic Regulations of Biopreparations” at Federal Medico-Biological Agency (SHES RCT&HRB of FMBA of RF), Serpukhov, Moscow region, Russia
Chamber Installation for concrete biocorrosion and other construction materials studies, developed in RCT&HRB fully meet the requirements of ISO. Chamber installation provides modeling of corrosive damaging conditions of any climatic zones (intensified damaging conditions), where ambient air could be saturated with saline, acid and other aggressive contaminants simultaneously, at a high level of adequacy. Up to 24 standard test-objects can be exposed for a long-term testing in the chamber installation at one time.
The body, the assemblies and details of the chamber installation are made from antirust materials (stainless style, glass, plastic, rubber, silicon).Externally the chamber is covered with heat-insulated material, whereas internally it is covered with antirust materials Operating volumes of the installation for test-objects and corrosive components of air to be put in, are tightly sealed and installed in a special box. The installation body and units are easily processed with any cleaning agents and liquid disinfectants.
Introduction
Materials corrosion issue covers a number of scientific, engineering, technical, architectural and construction and defense tasks dealing with economic and social-and-technical damage from corrosion.
Corrosive damage is closely connected and caused by variety of natural phenomena and human social and industrial activity. Among the factors intensifying materials corrosive damage the following are predominant: air temperature, air humidity, sun radiation, airflow rate, ambient air pollution with material-aggressive components (seawater salt, industrial acid emissions, bioaerosols as a result of human and animal vital functions) [1].
External factors influence kinds of material damage differently. Simultaneous effect of several factors is always observed in natural environment. An important factor combination is temperature and humidity complex, which becomes more intensive in polluted air (salt, acid vapor and microorganisms).
Information of microbiological factor role in materials corrosion is enlarged and generalized annually and economic damage from biological corrosion is assessed in a number of countries. Multiplicity of main kinds of microbial materials corrosion justifies its wide occurrence in various areas of human activity [2].
Microbiological corrosion of materials takes place in various conditions both in natural (soil, water and in above-water airspace) and industrial environment. Soil and water biocorrosion of materials are well studied whereas above-water airspace and atmospheric corrosion over aggressive pollutants remains not studied enough.
While more and more measures are taken to protect materials against biodamage, its methodology also becomes an acute issue as biodamage is a complex problem from scientific point of view and diversified in practice. Various techniques are employed to solve the problem of biodamage.
Till now no reliable techniques for assessment of materials corrosion intensity in adequate non-saturated conditions have been developed; no microorganism strains have been determined as most hazardous; no studies of intensifying conditions for materials biocorrosion have been carried out, and no effective protective means based on damaging factors integral characteristics have been suggested.
Studies of Russian and foreign microbiologists (Isachenko, 1951; Ivanov, 1964; Booth, 1971) proved the predominant role of Thiobacillus genus in oxidation of wide range of sulfur compounds to sulfates. So, thiobacteria are of importance as aggressive media creating factor [2, 3].
The research was continued by American and English scientists, who used aggressive corrosion function of thiobacteria for distraction the integrity and further degradation of concrete surface layer contaminated by radionuclides. Scientists and specialists from INEEL and BNFL developed a novel technique for thiobacteria use for degradation of concrete surface layer contaminated by radionuclides. Joint testing of the technique for concrete surfaces biological decontamination was carried out on nuclear power units of the USA and UK. The trials in EBR-1 nuclear reactor and INEEL storage facility demonstrated that rate of radionuclide-contaminated surface degradation ranges 4-8 mm per year, which justifies expediency of the technique wider application [4, 5, 6, 7, 8].
However, currently INEEL and BNFL consortium requires designing and testing of thiobacteria gel to be used not only for thiobacteria encapsulation but also for their growth stimulation providing durable nutrient substances and water (moistened air hygroscopic sorption).
Results
Aerosol chambers of the RCT&HRB facilities, perfect for development and trials of encapsulating gels for concrete biodecontamination, were considered suitable for biocorrosion processes modeling. The RCT&HRS has several aerosol chambers designed for atmospheric conditions imitation and some of them could be adopted for radionuclide-contaminated concrete biodecontamination purposes.
Engineering analysis resulted in joint INEEL–T2–2003–RU Project with INÅEL (Idaho National Engineering and Environment Laboratory), BNFL (British Nuclear Fuels Laboratory) and RTC&HRB (State Federal Enterprise for Science “Research Center for Toxicology and Hygienic Regulations of Biopreparations” at Federal Medico-Biological Agency) as participants.
Literature review helped to develop some basic requirements for novel chamber installations for high-speed corrosion testing of various materials:
- Chamber installations must provide homogeneous pollutant distribution in internal volume for uniform effect on test-objects;
- Liquid drops from top part of the chamber and higher-positioned specimens must not get to lower-positioned specimens;
- Pre-set working conditions must be provided and controlled during the whole testing session and corrosive agents concentration must be registered automatically and assessed by instrumental means;
- Temperature and relative humidity must be automatically regulated and constantly controlled;
- Temperature inside the chamber must be raised for 1 °Ñ per minute;
- Moistened air supply must provide pre-set relative humidity inside the chamber. Distilled water is only used for air moistening;
- Pre-set relative humidity inside the chamber must be created for no longer than 1-2 hours;
- Temperature and relative humidity control in the chamber must be accurate up to ± 2 ° Ñ and ± 5 %, correspondingly;
- Neither oil nor solid particles must be found in the sprayed air;
- If gaseous corrosive agent (ex. sulfur dioxide, carbon dioxide, etc) is used, concentration and homogeneity of the flow in test chamber must be controlled;
- Control techniques and allowances must comply with international requirements.
The designed at RCT&HRB chamber installation for concrete biocorrosion study meets the above-mentioned requirements entirely (Fig.1).
Fig.1. General looks of the chamber and automation controls of climatic conditions setting and pollutant sampling
1. chamber case 2. air heater ÑÂ-20-30, 3. freezer 4. automatic sampling system 5. executors with interface block 6. normalizers with humidity and temperature sensors 7. air heater temperature sensor 8. normalizers with pressure sensors 9. compressed air pipeline for air heater ÑÂ-20-30 10. compressed air pipeline for continuous heaters and aerosol generators 11. sampler 12. aerosol generator
The chamber installation allows to model adequate damaging corrosive conditions of any climatic zones (intensive damage), where ambient air may be saturated with combination of acid, saline and other aggressive pollutants. Up to 24 standard test-objects may be durably exposed in the chamber installation at a time.
The chamber installation case, units and parts are made of corrosion-resistant materials (stainless steel, glass, plastic, resin and silicone). The chamber is low-conductivity coated outside and corrosion-resistant inside. The chamber working volume, where the test-objects and corrosive air components are found, is sealed and placed in the special box.
The installation case and units may be treated with any washing and disinfecting (degassing) liquids.
The chamber installation is equipped with atomized aerosol generators can produce high-concentrated fine aerosol of any aggressive pollutant. The generators help to keep constant damaging effect as long as needed while a researcher may change pollutant composition and concentration or vary other damaging conditions.
To study materials biodamage in artificial conditions most successfully the regulated (15-40 °Ñ) temperature and airflow relative humidity (30-95 %) are set in the chamber installation and continuous pollutant delivery inside the chamber is provided.
The chamber installation is PC controlled and the chamber completely meets the requirements stated by G.S. Fomin and ISO: 6988, 7384, 8044 [9].
The installation design and manufacture was funded by CRDF within RBO-10309 Project.
References
1. Biodamage, biofouling and protection against it: Climatic, biochemical and eco-toxicological factors: Collection of work / Edited by B.V. Bocharov – Ì : Nauka, 1996. p.144
2. Microbial corrosion and its agents. Andeyuk Å.I., Bilay V.I., Koval’ E.Z., Kozlova I.À. – Kiev: Nauk. Dumka, 1980, p.288
3. Accute issues of bio-damage: Collection of work / Edited by B.V. Bocharov – Ì : Nauka, 1983. – p.240
3. “Vedeneev Institute”. Recommendations for assessment of microbiological factors effect on building concrete composition (final edition) approved by A.P. Beresnev, First Deputy Head of Division for Development Strategy and Scientific-and-Technical Policy of RSC “EEC of Russia”, St. Petersburg, 1998, p.20
4. Baboian R., Chaker V. How Corrosion Impacts Our Daily Lives, Our Safety and Our Economy //ASTM Standardization News. – 1998-#10, p. 28-31.
5. Idachaba M.A., Nyavor, N.O. Egiebor,R.D.Rogers. Development of a biofilm formation method for waste forms stability evaluation. Journal of Hazardous Materials B77 (2000), p. 133-147.
6. Idachaba M.A., Nyavor K., Egiebor N.O., Rogers R.D. A refinement of the biofilm formation method for waste forms stability evaluation.Journal of Hazardous Materials B84 (2001), p. 95-106.
7. Knight J., Cheeseman C., Rogers R. Microbial influenced degradation of solidified waste binder. Waste Management 22 (2002), p. 187-193.
8. Rogers R.D. Effects of microbially influenced degradation on massive geothermal fielconcrete structures. Biodegradation Systems Inc., 1206 Norton St. Idaho Falls, ID 83402, USA
9. Fomin G.S. Corrosion and corrosion resistance: International standards encyclopedia. – 2 edition, revised. – Ì.: IPK Izdatel’stvo Standartov, 1999. – p.520