Details

Autor(en) / Beteiligte

• Adnan, Tayyab

Titel

Engineering Properties and Durability of Belitic Calcium Sulfoaluminate (BCSA) Cement Concrete

Ort / Verlag

ProQuest Dissertations & Theses

Erscheinungsjahr

2024

Link zum Volltext

• ProQuest

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• Belitic calcium sulfoaluminate cement (BCSA) is a class of alternative cements used as a repair material (for its rapid strength gaining properties) for pavements and runways. More recently, researchers have investigated its use in structural concrete, where its low embodied energy and CO2 emissions relative to portland cement (PC) contribute toward infrastructure decarbonization. Additionally, the rapid-setting nature of BCSA favors accelerated construction, saving construction cost. However, a limited understanding of the fundamental structure and properties of BCSA composites hinders its practical adoption. This Ph.D. thesis investigates the engineering properties and durability (alkali-silica reactivity and chloride-induced corrosion) of BCSA concrete under conditions relevant to infrastructure construction.First, the thesis evaluates the engineering properties (compressive strength, tensile strength, and modulus of elasticity) of BCSA concrete, how they are influenced by concrete mixture parameters (w/cm and set retarder dosage) and curing age, and whether the tensile strength and modulus of elasticity are well predicted by concrete design codes. Compressive strength could be directly controlled by modifying water/cement ratio but extending the setting time with citric acid set retarders did not impact strength past the age of three days. In addition, the existing correlations from North American and European building codes provided good predictions of tensile strength and modulus of elasticity of BCSA concrete. Next, the thesis evaluates the alkali-silica reactivity of BCSA concrete, both experimentally and from a theoretical standpoint. Expansion tests with highly reactive aggregates revealed that ASR can and does occur in BCSA concretes, but it is less severe than in PC systems. Accelerated expansion tests produced misleading results; long-term expansion tests produced similar expansions in BCSA concrete with nonreactive and reactive aggregates. Microscopic investigations confirmed the presence of ASR cracks in BCSA mortars, although the ASR gel wasn’t observed. The improved ASR resistance of BCSA is attributed to the lower amounts of soluble calcium and the higher amounts of aluminum, causing a mitigation effect.Finally, the thesis evaluates the corrosion resistance of reinforced BCSA concrete by studying the chloride transport properties, chloride binding capacity, and corrosion performance. Electrical test methods indicated better performance than PC controls, but these results did not correlate with quantitative diffusion coefficients, possibly due to changes in pore solution chemistry. Chloride binding analysis indicates lower binding in BCSA cement concrete than in PC concrete. The pH of the pore solution was ~13 even at early age, suggesting good passivation of reinforcing steel. However, reinforced concretes exposed to chlorides corroded rapidly. This behavior was observed to be time dependent, however, as a longer curing period (90 or 180 days) produced similar corrosion resistance to the PC control.