Date of Award

Spring 12-21-2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Mark T. Hernandez

Second Advisor

Wil V. Srubar

Third Advisor

R. Scott Summers

Fourth Advisor

Fernando Rosario-Ortiz

Fifth Advisor

Dennis G. Grubb

Abstract

Unlike other construction materials like wood or steel, concrete possesses excellent resilience making it an ideal material for building structures to transport, contain and hold water. However, while concrete has been known for its durability, municipalities and wastewater utilities around the world now recognize that the concrete present in these essential infrastructure elements is becoming severely affected by biogenic corrosion, also known as microbially induced concrete corrosion (MICC). This phenomenon is not new, it has been acknowledged as a potential problem for over a hundred years [1]. The microorganisms responsible for this corrosion, have been linked to the generation of sulfuric acid from common sewer gases. This biogenic acid promotes dissolution of calcium-containing minerals (i.e. calcium-silicate-hydrates (C-S-H) and calcium hydroxides (Portlandite)) responsible for the strength of the concrete structures. In response, concrete protection methods have been developed to include new formulations that obtain more impermeable concrete, protective coatings and paintings on concrete surfaces, and the use of impermeable plastic liners. All these technologies focus on developing acid resistant materials instead of attacking the primary cause: acidogenic sulfur-oxidizing bacteria (SOBs). Little research has been conducted on materials which limit or inhibit the activity of these acidophilic bacteria. One of the most recent and promising approaches to inhibit SOBs is the substitution of metal-laden granular activated carbon (GAC) particles and basic oxygen furnace steel slag (BOF-S) for a fraction of the fine aggregates traditionally used in cement-based materials. While the antimicrobial properties of these replacements have been demonstrated [2], there are no studies related to the effects that these substitutions may have on the microstructural and mechanical properties of the cement-based materials. In response to this research gap, the central aim of this work was to study the effects that these antimicrobial aggregates (i.e. metal-laden GAC or BOF-S particles) have on ordinary Portland cement formulations. A comprehensive characterization of these antimicrobial aggregates was completed along with stringent characterization of the mechanical properties (compressive and tensile strengths), effects on microstructure (porosity, mineralogy), metal mobilization (elemental microprobe analysis), workability (flowability, setting times) and early hydration reactions (isothermal calorimetry).

Available for download on Thursday, January 27, 2022

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