?Off-spec? Fly Ash in Concrete Applications
Mentor 1
Konstantin Sobolev
Location
Union Wisconsin Room
Start Date
5-4-2019 1:30 PM
End Date
5-4-2019 3:30 PM
Description
Coal combustion residuals (CCR) are the solid residues generated by coal-burning electric utilities, which are commonly used in concrete applications. These consist primarily of fly ash (Class C or F) that is commercially used in a variety of concrete applications to improve performance. Landfilled or impoundment fly ash with high carbon content and spray dryer absorber ash (SDA) containing high concentrations of sulphates represent two major off-spec CCR materials that need to be addressed. High carbon contents can lead to problems with durability such as permeability and accelerated freeze/thaw degradation. At the same time high sulphate levels can result in low sulphate resistance and structural decomposition due to sulphate attack.
Current research indicates that combining these two off-spec materials helps to offset the unfavorable effect of high concentrations of sulphates and carbon. It is also an potentially efficient and green solution because it may be able to replace up to 70 percent of the portland cement, which is a significant contributer to global carbon emissions. Presented herein are the results of selected research results obtained using cement pastes, mortars and concrete mixtures with different formulations. The results include fresh properties (e.g., flowability, setting time heat of hydration and density) and hardened properties (e.g., compressive/flexural strength, permeability and visual signs of decomposing or dimensional distortion). Also presented is an overview of the test methodologies and procedures used to obtain these results.
?Off-spec? Fly Ash in Concrete Applications
Union Wisconsin Room
Coal combustion residuals (CCR) are the solid residues generated by coal-burning electric utilities, which are commonly used in concrete applications. These consist primarily of fly ash (Class C or F) that is commercially used in a variety of concrete applications to improve performance. Landfilled or impoundment fly ash with high carbon content and spray dryer absorber ash (SDA) containing high concentrations of sulphates represent two major off-spec CCR materials that need to be addressed. High carbon contents can lead to problems with durability such as permeability and accelerated freeze/thaw degradation. At the same time high sulphate levels can result in low sulphate resistance and structural decomposition due to sulphate attack.
Current research indicates that combining these two off-spec materials helps to offset the unfavorable effect of high concentrations of sulphates and carbon. It is also an potentially efficient and green solution because it may be able to replace up to 70 percent of the portland cement, which is a significant contributer to global carbon emissions. Presented herein are the results of selected research results obtained using cement pastes, mortars and concrete mixtures with different formulations. The results include fresh properties (e.g., flowability, setting time heat of hydration and density) and hardened properties (e.g., compressive/flexural strength, permeability and visual signs of decomposing or dimensional distortion). Also presented is an overview of the test methodologies and procedures used to obtain these results.
