Non-destructive chemical analysis of water and chlorine content in cement paste using near-infrared spectroscopy

Chloride induced deterioration of concrete structures is well underway when the damage is visually detected during inspection. If such damage was identified using a non-destructive method, inspection costs would reduce significantly. We tested the use of near-infrared (NIR) spectroscopy for non-destructive multicomponent analysis of cement pastes. Cement paste samples with varying chloride-ion concentrations and humidity were prepared for different cement types. Reflectance spectra were obtained, then total moisture content (v/v) and chloride ion concentrations were measured using destructive testing as a reference. A correlation was observed between the measured water amount/chloride ion concentration and respective NIR absorption values.