Evaluation of Microbially-Influenced Degradation of Massive Concrete Structures

Abstract

Corrosion of massive concrete structures is a costly and environmentally dangerous problem. Many low level waste disposal vaults, both above and below ground, are constructed of concrete. When the integrity of these structures is compromised, potential for soil and water contamination is significantly increased. There are literally thousands of massive concrete structures within the U.S. infrastructure that are in a serious state of disrepair due to corrosion. One potential contributing agent to the destruction of concrete structures is microbially-influenced degradation (MID). MID occurs when microorganisms in the environment produce mineral or organic acids that dissolve or disintegrate the cement matrix. Three groups of bacteria are known to create conditions that are conducive to destroying concrete integrity. They are sulfur oxidizing bacteria, nitrifying bacteria, and heterotrophic bacteria.Research is being conducted at the Idaho National Engineering Laboratory to assess the extent of naturally occurring microbially influenced degradation (MID) and its contribution to the deterioration of massive concrete structures. The preliminary steps to understanding the extent of MID, require assessing the microbial communities present on degrading concrete surfaces. Ultimately such information can be used to develop guidelines for preventive or corrective treatments for MID and aid in formulation of new materials to resist corrosion. An environmental study was conducted to determine the presence and activity of potential MID bacteria on degrading concrete surfaces of massive concrete structures. Scanning electron microscopy detected bacteria on the surfaces of concrete structures such as bridges and dams, where corrosion was evident. Enumeration of sulfur oxidizing thiobacilli and nitrogen oxidizingNitrosomonas sp.andNitrobacter sp.from surface samples was conducted. Bacterial community composition varied between sampling locations, and generally the presence of either sulfur oxidizers or nitrifiers dominated, although instances of both types of bacteria occurring together were encountered. No clear correlation between bacterial numbers and degree of degradation was exhibited.

Review of Concrete Biodeterioration in Relation to Buried Nuclear Waste

“…It will focus more on the types of microbial physiologies and effects, with less attention to species names, since it is important to pay more attention to environmental niches than any particular species for several reasons. Due to species richness in the environment and our dearth of information regarding microbial species in the environment, it is likely that significant species variability will exist from place to place even though the same biogeochemical processes are occurring [5,13]. Our findings are meant as a guide for use by environmental modelers for determination of, and prediction of, the stability of concrete structures in various environments.…”

“…Since then, biodegradation of concrete structures was demonstrated to be a common occurrence; however, various microbial populations and mechanisms were shown to play different roles at different locations [5][6][7]. As a result, microbial assays designed to determine the rate of concrete biodegradation proved useful in evaluating concrete properties but were not a good predictor of environmental impacts on concrete [8,9].…”

Increasing the Biostability of Concrete by the Introduction Of Additives

“…As a result of biocorrosion, the porosity of concrete increases [6,12,13] and diffusion processes accelerate, which contributes to the development of corrosion processes [14][15][16][17]. The reaction of biogenic acids and other products of the vital activity of microorganisms with the components of the cement stone of concrete leads to the destruction of the structure.…”

Review of concrete biodeterioration in relation to nuclear waste

“…This literature review focuses on the biodegradation of concrete, paying particular attention to the 84 various physiological aspects of microorganisms that control concrete biodegradation and also the 85 physical and chemical parameters that control microbial activity. Due to species richness in the 86 environment and our dearth of information regarding microbial species in the environment, it is 87 likely that significant species variability will exist from place to place even though the same 88 biogeochemical processes are occurring (Hamilton et al, 1996;Silva, 1996) hence, the focus is 89 more on the types of microbial physiologies and effects, with less attention to species names. 90…”