Raman spectroscopy analyses of road construction materials

Significance of the Topic

Road construction materials such as pigments, resins, and fillers play a critical role in ensuring durability, visibility, and safety of road markings and surfaces. Rapid, on-site verification of these materials aids quality control, prevents material mix-ups, and supports maintenance operations.

Objectives and Study Overview

This study aimed to demonstrate the capability of a handheld Raman analyzer (Mira M-1) to differentiate common roadmaking substances: calcium carbonate (chalk), titanium dioxide, various pigments (yellow, blue, red), and resins (EPONAC®, TP, DEGALAN®). Spectral profiles were collected and compared to highlight unique vibrational signatures of functional groups.

Methodology and Instrumentation

The Mira M-1 Raman spectrometer with 785 nm laser and Orbital-Raster-Scan (ORS) technology was employed in automatic acquisition mode. Samples were placed in glass vials held by an adapter. Spectra were recorded under auto-determined integration times, enabling nondestructive analysis through container walls.

Main Results and Discussion

Calibration spectra revealed distinctive peaks for each material:

• Calcium carbonate: strong bands at ~712 cm⁻¹ (O–C–O bending) and ~1087 cm⁻¹ (O–C–O symmetric stretch).
• Titanium dioxide (rutile): O–Ti–O stretching at 446 cm⁻¹ and Ti–O at 609 cm⁻¹; absence of splitting distinguishes rutile from anatase.
• EPONAC® resin: multiple aromatic and aliphatic vibrations, notably benzene ring modes (640, 819 cm⁻¹), C–OH stretch (1113 cm⁻¹), and C=C at 1609 cm⁻¹, confirming a bisphenol A copolymer structure.
• DEGALAN® resin: ester carbonyl peak at 1728 cm⁻¹, COO bending at 599 cm⁻¹, and C–O vibrations (1065, 1125 cm⁻¹), indicating a propionate-based polyester.
• Pigments: characteristic fingerprint regions allowed clear distinction from resins based on aromatic and inorganic lattice vibrations.

Benefits and Practical Applications

Handheld Raman analysis enables:

• Fast material identification on site without sample preparation.
• Verification of raw materials and final products during road construction.
• Distinction between similar-looking pigments and polymers, reducing the risk of specification errors.

Future Trends and Opportunities

Advances may include integration with augmented reality for immediate spectral interpretation, expansion of spectral libraries covering novel polymers and additives, and coupling with AI algorithms for automated classification. Miniaturized Raman systems could be deployed on vehicles for continuous monitoring of road surface coatings.

Conclusion

Handheld Raman spectroscopy with the Mira M-1 offers a reliable, nondestructive approach to differentiate and verify road construction materials. Distinct spectral features of pigments, fillers, and resins facilitate rapid quality control, supporting safer and more efficient infrastructure projects.

Reference

Metrohm AG. Raman spectroscopy analyses of road construction materials. AN-RS-004.