Graduate Thesis Or Dissertation

 

Automated Chemical Acidification Testing of Cementitious Materials Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/qf85nj79w

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  • Due to its availability, versatility, structural capability, and economic advantages, concrete is the most widely used material in building sewer networks and other wastewater structures such as treatment stations, wastewater digesters, septic tanks, pumping stations, hydraulic risers, utility risers and covers, etc. Concrete structures exposed to sewer environments can experience Microbially Induced Corrosion of Concrete (MICC), which is multi-stage biological deterioration process. Three main testing procedures are typically used to assess MICC of paste, mortar, or concrete: 1) the biological chamber test that uses hydrogen sulfide (H2S), 2) the biogenic acidification test without H2S presence, and 3) the chemical acidification test, which is economical and straightforward to set up. These tests simulate the environment of MICC in different ways to study the corrosion process. The first part of the thesis focuses on the primary concern of the chemical acidification test, which is the rapid rising of the pH in the exposure solution due to the leaching of calcium compounds from the cementitious materials. A holistic approach was developed to stabilize the pH of the exposure solution, to measure corrosion parameters with minimal disturbance to the test, and to establish a relationship between the chemical acidification test and the theoretical systems widely used in the industry to calculate the service life of concrete. To quantify MICC, many researchers attempt to measure mechanical properties of the concrete after exposure to the corrosive environment. Ball-on-three-ball (B3B) flexural strength test had been recognized as the most robust test in a way that it has multiple advantages over its counterparts. The second part of this thesis addresses the questions that have surfaced with the recent adoption of this test method in ASTM C1904-20. The first question is whether the technique of mixing used in sample preparation impacts the results. It was found that the use of vacuum mixing (ASTM C1904-20) and Hobart mixing (ASTM C277, C305) provide comparable results; however, the high-shear mixing (ASTM C1738) is statistically different. The second question is how rapidly the B3B test sample needs to be tested after removal from the solution to minimize the impact of drying. It was found that the sample should be removed and tested within ten minutes to reduce variation. These results will provide information needed to evaluate changes for ASTM C1904-20.
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