Date of Graduation

5-2021

Document Type

Thesis

Degree Name

Master of Science in Civil Engineering (MSCE)

Degree Level

Graduate

Department

Civil Engineering

Advisor/Mentor

Cameron Murray

Committee Member

Micah Hale

Second Committee Member

Richard Deschenes

Keywords

accelerated C1012 method, ASTM C1012, BCSA, belitic calcium sulfoaluminate cement, concrete, microbially induced corrosion, sodium sulfate solution, sulfate attack, sulfuric acid

Abstract

Microbially induced corrosion (MIC) is a fairly common concrete deterioration mechanism with many negative effects. MIC is a complex chemical and biological process that occurs in sewage systems and is nearly impossible to replicate in a laboratory setting. For this study, sulfate and sulfuric acid attack on concrete were studied to mimic two stages of the MIC process. The ASTM C1012, Standard Test Method for Length Change of Hydraulic-Cement Mortars Exposed to a Sulfate Solution and a modified ASTM C1012 accelerated method were used to compare the sulfate resistance of belitic calcium sulfoaluminate (BCSA) cement, portland cement (PC), and PC-fly ash blends. The effect of citric acid dosage on sulfate resistance of BCSA cement mixtures was also studied. The standard method was used primarily for comparison to the accelerated method results. Mortar bar expansion and mass change were analyzed to examine the sulfate resistance of varied BCSA mixtures. The most sulfate-resistant mixes contained BCSA cement or a blend of PC and class F fly ash. Citric acid dosage did not seem to affect resistance of BCSA cement to sulfate attack. Resistance of PC, PC-fly ash blends, and BCSA cement to a sulfuric acid solution was also compared. Compressive strength, mass change, and volumetric changes were measured after prolonged immersion in sulfuric acid. Water to cementitious material (w/cm) ratios and curing time for BCSA were also compared to resistance to sulfuric acid attack. The most resistant mix contained a blend of PC and class F fly ash. A higher w/cm was found to be more resistant against sulfuric acid attack when using BCSA, while differing cure times did not clearly indicate sulfuric acid resistance.

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