Use of Raman spectroscopy to characterize the effect of nanomagnetite as an addition to Portland cement paste on mitigating internal sulfate attack

摘要

Cement pastes containing nanomagnetite and pyrite were exposed to oxygen and moisture for 90 days. The paste containing pyrite showed evidence of internal sulfate attack, through a reduction in mechanical strength and presence of microcracks with ettringite verified by FEG SEM/EDS. Nanomagnetite increased the mechanical strengths, verified by the pore filling and formation of more chemically stable compounds in the matrix, such as hydrated C(4)AF. One percent nanomagnetite was the most effective concentration to mitigate the effects of internal sulfate attack. Raman spectroscopy is a differentiated technique for identifying nanomagnetite, pyrite oxidation product and low crystallinity compounds, such as C-S-H. (C) 2020 Elsevier Ltd. All rights reserved.