Laser-induced breakdown spectroscopy (LIBS) for the characterization of demolition waste: an exploratory study

Laser-induced breakdown spectroscopy (LIBS) is a fast, and non-destructive technique for real-time elemental analysis, ideal for in-line characterization of construction and demolition waste (CDW). This study evaluates and improves the accuracy of portable LIBS for elemental quantification in pressed pellets from CDW. Pressed powder pellets of different CDW categories (i.e., cements, concrete, masonry), previously analysed by X-ray fluorescence (XRF), were measured using the SciAps Z900 handheld LIBS spectrometer. Approximately 80 selected samples were used to build a new library dataset based on a matrix-matching calibration (MMC) approach. The resulting MMC library was then compared with the built-in SciAps “Geochem” library, which is designed for inorganic-mineral rock matrices. MMC method shows higher Si and Ca levels with similar concentrations, as main components of mixed CDW materials. Results show that MMC reduces matrix effects and analyte signal interference, enabling accurate elemental quantification, particularly for CDW samples dominated by high Si (20–70 wt%), and Ca contents (10–75 wt%). The accuracy and measurements of Ca contents are better for both MMC and Geochem calibration (GC) models, although the average relative difference decreases from 10.9% (GC) to 4.55% (MMC). Comparable accuracy improvements are found for other major elements (Si, Al, Ti, Fe, Mn, Mg, Na, K). To further validate MMC-library performance, certified reference materials from the National Institute of Standards and Technology (NIST) for building materials were also analysed. Our findings suggest that the MMC approach improves both the accuracy and precision of LIBS measurements on pressed pellets from CDW.