Hyperspectral reflectance spectroscopy for rapid nondestructive microstructural evaluation of high strength internally cured concrete

The utilization of high-strength concrete (HSC) incorporating internal curing (IC) has been experiencing a significant surge in the construction industry. Even though several studies have reported the identification and utilization of various polymers as IC agents, the efficacy and optimization of dosages in using polyethylene glycol (PEG) as IC agent is not well understood. Further, the methods used for quality assessment of the HSC are generally static and are laboratory based. This study investigates the efficacy of IC using PEG 4000 and 6000 at optimized dosages for enhancing the microstructure and water absorption characteristics of HSC, and presents a new method of assessment of the quality of HSC using hyperspectral reflectance spectroscopy (HRS). Apart from identifying the distinct spectral absorption features and regions of wavelength, a quantitative method, concrete quality metric (CQM) is presented for numerical assessment of the quality. Sample of IC-HSC exposed under various regimes of curing were assessed using the sorptivity test, scanning electron microscope and the proposed HRS technique. Sorptivity testing revealed significant reductions in water absorption for IC specimens compared to conventionally cured and non-cured mixes. These findings underscore the efficacy of PEG in improving concrete quality, providing a comprehensive understanding of IC mechanisms. Exhibiting distinct spectral reflectance patterns at distinct wavelength and numerical value of CQM indicative of porosity status, the results suggest that HRS can be a rapid and non-contact method for quality assessment of IC-HSC.