Graduate Thesis Or Dissertation
 

Assessment and Service Life Prediction of Microbial Induced Corrosion of Concrete (MICC)

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/k930c540d

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  • Microbial-induced corrosion of concrete (MICC) is a multi-stage deterioration process caused by microbial activity in wastewater infrastructure. MICC is a worldwide issue due to the reduced service life of the wastewater infrastructure and the economic impact associated with increased maintenance and reconstruction costs. This thesis explores two critical aspect of this complex and costly problem. The first thrust of this research is related to the service life prediction of concrete used in wastewater sewers using the data from standardized benchtop biogenic acidification tests. The second thrust explores the role limestone addition in cementitious mixtures during the acidification process, with a focus on portland-limestone cement. Microbially induced corrosion of concrete is a multi-stage deterioration process influenced by the presence and activities of bacteria in wastewater collection, storage, and treatment infrastructure. MICC reduces concrete service life significantly and is a serious issue due to enormous cost and environmental effects. Conventional accelerated laboratory methods may not accurately represent the rate of concrete deterioration that occur in field conditions. However, recently, a biogenic benchtop method for assessing MICC has been developed and standardized (ASTM 1904-20). This new approach does not rely on H2S as the nutrient source for the sulfur oxidizing bacteria, but rather uses elemental sulfur species, therefore, it is practical, safer, and rapid. The objective of this study is to develop a service life modeling approach to study MICC to correlate the results of the ASTM 1904-20 approach to real field conditions such as whose found in sewer pipes. This correlation is based the Pomeroy model that relates the field H2S concentrations, wastewater flow conditions, geometry and the properties of the concrete. The model will be provided by using ‘correlation factors” and a demonstration study showing how the ASTM C1904 data could be used to predict the performance of different types of concrete and antimicrobial products in realistic exposure scenarios will be explained. The second thrust of this work analyzes chemical acidification in cement pastes made where a portion of the clinker is replaced with limestone (LS, calcium carbonate). This research addresses the question of how ASTM C595 cements (more specifically portland-limestone cement) respond to acid exposure as compared with ASTM C150 cements. To answer this question, the performance of OPC, OPC+LS systems respond when exposed to acid at a pH of 2 and 3. The degradation of the material was measured over time using thermogravimetric analysis (TGA) to assess calcium hydroxide (Ca(OH)2) and calcium carbonate (CaCO3) changes as well as flexural strength reduction. Results indicate that there was no significant difference between the flexural strength and CH loss of different limestone mixtures during pH~3 immersion of 42 days. The flexural strength and TGA results have become more distinctive for more severe acidic conditioning at pH~2. The consumption of titration solution to keep the pH constant was correlated with the consumption of Ca(OH)2 and CaCO3 by using TGA results. When clinker is replaced with CaCO3 the sacrificial characteristic of CaCO3 offsets dilution. The use of limestone changes the hydration products and produces monocarbonate instead of monosulfate phase, which might affect the reaction of hydration products with sulfuric acid.
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  • Ongoing Research
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  • 2023-01-08 to 2023-08-08

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