Imperial College London
Portrait Picture

Professor Hong S. Wong

Faculty of Engineering, Department of Civil and Environmental Engineering

Professor of Concrete Materials
 
 
 
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Contact

 

+44 (0)20 7594 5956hong.wong Website

 
 
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Assistant

 

Ms Ruth Bello +44 (0)20 7594 6040

 
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Location

 

228DSkempton BuildingSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{Zhang:2022:10.1617/s11527-022-01979-9,
author = {Zhang, K and Yio, M and Wong, H and Buenfeld, N},
doi = {10.1617/s11527-022-01979-9},
journal = {Materials and Structures},
pages = {1--18},
title = {Optimising confocal Raman microscopy for spectral mapping of cement-based materials},
url = {http://dx.doi.org/10.1617/s11527-022-01979-9},
volume = {55},
year = {2022}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - Raman spectroscopy combined with confocal imaging, i.e. confocal Raman microscopy (CRM) is a relatively new technique with huge potential for high-resolution chemical mapping of phase composition and spatial distribution in cement-based materials. However, the effects of sample preparation and various operating parameters on mapping quality has not been systematically studied. This paper optimises CRM for spectral mapping of carbonated and non-carbonated cement-based materials. The effects of sample preparation and scanning parameters on the detection of four main phases (calcite, portlandite, ettringite and unreacted cement) were investigated. Results show that although freshly cut cementitious samples can be analysed as-is, the Raman signals improve with short gentle drying and surface grinding/polishing prior to analysis. Increasing laser power, exposure time and scan accumulation, and short laser wavelength yields higher signal-to-noise (SNR) ratio in the obtained spectrum. The use of a 4.15 mW laser power, 2 s exposure time and scan accumulation of 2 with 532 nm laser represents a good operating condition for Raman analysis of cement-based materials. This produces SNR > 10 for all investigated phases at short testing time and low risk of laser-induced damage. Microcracking caused by localised heating during closely-spaced mapping can be limited by impregnating the sample with epoxy to protect the microstructure. We show for the first time that CRM can be used to quantify the volume fraction of calcium carbonate and portlandite at high resolution when combined with SEM. The advantages and limitations of CRM for mapping cement-based materials are discussed.
AU  - Zhang,K
AU  - Yio,M
AU  - Wong,H
AU  - Buenfeld,N
DO  - 10.1617/s11527-022-01979-9
EP  - 18
PY  - 2022///
SN  - 1359-5997
SP  - 1
TI  - Optimising confocal Raman microscopy for spectral mapping of cement-based materials
T2  - Materials and Structures
UR  - http://dx.doi.org/10.1617/s11527-022-01979-9
UR  - https://link.springer.com/article/10.1617/s11527-022-01979-9
UR  - http://hdl.handle.net/10044/1/97037
VL  - 55
ER  -
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