The Effect of Baghouse Dust from Secondary Aluminum Processing Waste on Cement Hydration and Mechanical Properties

Abstract

This work studies the mechanical and chemical effects of utilizing baghouse dust (BHD) from secondary aluminum processing waste as a cement additive for potential use in concrete materials. The baghouse dust was added to cement pastes at replacements of 4 % and 8 % by cement mass. In addition, a combination of BHD and silica fume at different blended ratios were added to the cement mixture as a combined additive. Some reference proportions were also prepared for a comprehensive comparison. Unconfined compressive strength and the chemical composition of the extracted pore solution of the abovementioned hardened cement pastes were investigated. In addition, the effect of BHD on the hydration characteristics of the cement paste was also observed through isothermal calorimetry. It was found that an 8 % substitution of cement by BHD resulted in increased compressive strength after 1 day and 3 days of curing and a reduction of less than 2 % at 7 days of curing. Comparatively, samples with 8 % silica fume resulted in a strength increase of 17 %. As such, it was concluded that BHD addition of up to 8 % was not detrimental to concrete strength but did not improve performance either. This finding was supported by isothermal calorimetry data, which showed that the addition of BHD and the addition of silica fume both increased the initial peak of hydration and accelerated the hydration process but did not significantly impact the total energy of hydration over a period of 7 days. Finally, the high chloride content in BHD may promote corrosion in steel bars and increase concrete scaling potential.