Quantifying volcanic glass powder in cementitious systems using PONKCS-Rietveld analysis

Volcanic glass powder (VGP) has emerged as a promising supplementary cementitious material (SCM) due to its pozzolanic reactivity and potential to enhance the microstructure of cementitious systems. Accurate quantification of the VGP glass content is essential for understanding its reaction kinetics and optimizing its use in concrete. This study evaluates the efficiency and accuracy of the partial or no known crystal structures (PONKCS) method for quantifying VGP glass, offering a practical alternative to time-consuming selective dissolution experiments. Results show that the PONKCS-Rietveld analysis provides reliable quantification, with deviations within ± 2 wt.% compared to the selective dissolution method. In a simplified system of VGP mixed corundum, the method demonstrated high accuracy across a range of VGP glass contents, confirming its robustness under controlled conditions. However, in hydrated VGP–OPC systems, when the VGP content falls below 10 g/100 g ignited binder (corresponding to a VGP reaction degree of 40%), quantification errors increase due to changes in the full width at half maximum (FWHM) of the C-S-H peak at 29.4°, influenced by the pozzolanic reaction of VGP. These findings contribute to the refinement of PONKCS-Rietveld analysis for VGP glass, supporting its application in the precise evaluation of VGP-containing cementitious systems.