Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

External sulfate attack is a complex process that can result in concrete structures deteriorating prematurely. This dissertation describes a comprehensive evaluation of factors influencing external sulfate attack and includes both laboratory and field investigations. Significant emphasis was placed on evaluating the sulfate resistance of mortar and concrete containing high-calcium fly ash (Class C fly ash as per ASTM C 618). This investigation showed that these fly ashes generally reduced the sulfate resistance of mortar and concrete, but that sulfate resistance was possible through the incorporation of other supplementary cementing materials (silica fume and ultra fine fly ash) into these mixtures. Another key area of emphasis in this project was the correlation between accelerated laboratory tests and outdoor exposure site performance. The behavior of concrete exposed to various sulfate salts (sodium, magnesium, and calcium) was evaluated, both in static immersion tests and in outdoor sulfate trenches. It was found that the distress outdoors was exacerbated by physical sulfate attack, especially when concrete was exposed to sodium sulfate. It was found that lowering the water-tocementitious ratio (w/cm) and incorporating appropriate dosages of suitable supplementary cementing materials improved resistance to both chemical and physical forms of sulfate attack. Lastly, a comprehensive study of bridges throughout Texas discovered concrete structures suffering from possible external sulfate attack. The use of analytical techniques such as x-ray diffraction (XRD) and scanning electron microscopy (SEM) were used throughout the study to determine the presence of hydration products that may form with mortars and concrete specimens. Findings from this research will be implemented in specifications in Texas for the use of Class C fly ash use in concrete in areas that may have sulfate soils and groundwater.

No description available.

Un problema común en las paredes del primer piso es la presencia constante de eflorescencias, que es un desperdicio de sal polvoriento, frecuentemente blanco como la tiza. Esto sucede cuando un ambiente húmedo (suelo sulfatado) disuelve las sales de calcio del concreto y migran a la superficie por capilaridad. Ahora bien, un fenómeno como este podría ser fatal para la construcción, debido a la degradación del material y también para la salud humana. Hoy en día, la gente repara estas apariciones blancas, pero tienden a reaparecer. Por ello, el cemento MS se utiliza para evitar que esto ocurra, pero para ambientes muy agresivos los aditivos son la mejor opción, salvo por su precio. Es por ello que en esta investigación se produjeron y analizaron cilindros de concreto y vigas de mortero de 2 diseños. Estaban compuestos por agregado fino y grueso, cemento MS y emulsión asfáltica (aditivo bituminoso) al 0%, 10%, 20% y 30% del peso del cemento. Ensayos como la resistencia a la compresión, absorción capilar y la exposición acelerada a sulfatos fueron fundamentales para probar la viabilidad de la propuesta, es decir, la cantidad óptima de emulsión. Además, se concluyó que las muestras con 10% y 20% de emulsión asfáltica pueden ser funcionales para fines estructurales (cimentaciones) y no estructurales (recubrimientos), debido a la resistencia a la compresión alcanzada y en comparación con las tradicionales tiene mejor defensa contra los sulfatos. / A common issue on the first-floor walls is the constant presence of efflorescence which is a dusty salt waste, frequently white like chalk. This happens when a humid environment (sulfated soil) dissolves calcium salts of concrete and migrate to the surface by capillarity. Now, a phenomenon like this could be fatal for the construction due to material demotion and also for human health. Nowadays, people repair these white things but they tend to reappear. There for, MS cement is used to prevent this to occur, but for highly aggressive environments additives are the best option, except for its price. That is why in this research, concrete cylinders and mortar beams of 2 designs were produced and analyzed. They were made up of fine and coarse aggregate, MS cement and asphalt emulsion (bituminous additive) of 0%, 10%, 20% and 30% by weight of the cement. Experiments like compressive strength and accelerated exposure to sulfates were fundamental to prove the viability of the proposal, ergo the optimum amount of emulsion. Furthermore, it was concluded that samples with 10% and 20% of asphalt emulsion can be functional for structural (foundations) and non-structural (overlays) purposes because of the reached compressive strength and compared to traditional ones it has better defense against sulfates.