A Raman spectroscopy study of steel corrosion products in activated fly ash mortar containing chlorides

• The corrosion products were iron oxyhydroxides, goethite and lepidocrocite.
• Raman spectra were obtained with 532 nm and a power from 0.025 to 0.25 mW.
• Raman spectra were obtained with 633 nm and a power greater than 2.5 mW.
• For 532 nm line the phases formed were transformed into hematite at above 0.5 mW.
• For the line of 532 nm with 5 mW showed fluorescence.

Raman spectroscopy was used to characterise the corrosion products of reinforcing steel embedded in activated fly ash mortars in the presence of 0.4% and 2% chlorides. Two alkaline solutions with different soluble silica contents were utilised to activate the fly ash. Raman spectra were obtained using two excitation wavelengths (532 and 633 nm) and making power scans to select the suitable conditions of register for each wavelength. The main steel corrosion products identified were iron oxyhydroxides with low crystallinity, goethite (α-FeOOH) and lepidocrocite (γ-FeOOH). These products need to be studied using a spectrometer with the laser line of 532 nm at low powers from 0.025 to 0.25 mW or a spectrometer with the laser line of 633 nm at high power between 2.5 and 25 mW.