Date of Award
Doctor of Philosophy (PhD)
Dr. Prasad Rangaraju, Committee Chair
Dr. Amir Poursaee
Dr. Bradley Putman
Dr. Laura Redmond
Since cement production is responsible for a significant share of anthropogenic CO2 emissions, the sustainability of concrete construction has become one of the most targeted research and construction industry goals. Many suggestions have been in use to encourage sustainability of concrete construction; one such approach is to partially replace cement by industrial byproducts. The most known industrial byproduct used in concrete construction worldwide has been fly ash, which is a byproduct of burning coal for power generation.
Fly ash use in concrete has various benefits. It reduces the water demand, reduces plastic shrinkage, reduces permeability, and thus improving the durability of concrete against the ingress of chemicals such as sulfates and chlorides, increases the ultimate strength, and by replacing cement, the alkalinity of pore solution would decrease to a level at which alkali-silica reaction (ASR)-induced cracks could be less likely. However, the use of fly ash does have some setbacks. For example, it reduces the early-age strength development, and, with some types of fly ashes, higher cement replacement ratios are needed to achieve better performance in concrete durability problems, which affects the setting time and early-age strength. Moreover, the volume of the available fly ash is dwindling as power companies move towards more sustainable fuels for generating power. Lastly, a significant amount of fly ash that does not meet ASTM C618 specifications for use in Portland cement concrete (i.e., Off-spec fly ashes) has been stored in facilities known as ash ponds. These ash ponds have been problematic to the environment, causing soil and groundwater contamination in locations where they are not adequately secured. There have also been incidents where hurricanes or tornadoes have caused ash pond spills, and the leached hazardous materials polluted water streams and rivers.
Therefore, optimizing the use of current fly ash resources and/or search for alternatives to fly ash is essential. One of the substitutes that has not been considerably examined for beneficial uses is the fiberglass waste from the production of glass fibers used in composite materials. This material's performance is superior as a pozzolan, compared to fly ash, in portland cement concrete (PCC), and as an effective precursor for geopolymer concrete (GC) when it is finely ground.
Therefore, the objective of this work, in its first stage, is to investigate the use of ground glass fibers (GGF) in binary and ternary blends with fly ash (in-spec and off-spec); so both materials could be used as either SCMs in PCC or as precursors in GC. In the second stage, to promote the use of these two industrial wastes, one application where selected blends of FA+GGF can be utilized was investigated. This application was the Full Depth Reclamation (FDR) of asphalt pavements, where a considerable amount of cement is used in pavement rehabilitation projects.
The first stage of this study revealed that the ternary blend of GGF with the in-spec fly ashes in PCC had significantly improved both fresh and hardened properties of mortar and concrete. The GGF-containing mixtures' superior performance was confirmed as they had higher early compressive strength, even at a high replacement ratio of 40% in both mortar and concrete. The early-age strength development was enhanced, and the drying shrinkage was reduced for the ternary blended concrete when compared with the performance of binary fly ash blended concrete. The ultimate compressive and tensile strengths were much improved compared to the pure cement concrete. The ternary blend significantly helped in mitigating ASR and resisting sulfate attack and chloride ion penetration.
Amer, Omar Alsanusi, "Development and Application of Sustainable Binders Comprising of Fly Ash and Ground Glass Fibers in Portland Cement and Geopolymer Concrete" (2020). All Dissertations. 2833.