THE PHASE ADDITION METHOD TO EVALUATE RIETVELD MINERAL QUANTITATIVE ANALYSIS OF HYDRATED CEMENTS

X-ray powder diffraction (XRPD) analysis combined with the Rietveld method is commonly used in the mineralogical quantification of a range of different samples, including soil, rocks, and many industrial materials. The combination of this technique with the addition method, i.e. the successive addition of a mineral phase to the investigated sample, offers a simple and reliable method to test Rietveld results without the need for third techniques. Four different hydrated cement samples were successive mixed (at 1, 5, and 10%) with one of the main mineral-related phases (ettringite, larnite, ternesite, or ye’elimite) occurring in them. The Rietveld quantified amounts of these phases show a very good agreement with their added amounts, all resulting in regression lines with R2>0.99. The respective line equations permitted the calibration of the quantified amounts of the studied mineral phases, which presented standard deviations lower than 0.3. Keywords: Rietveld; addition method; hydrated cement, calcium sulphoaluminate.