Clinkers, a component of cements, are created by mixing and calcinating limestone, clay and silica sand. The amount of free lime (calcium oxide) is an important factor to confirm the clinker’s degree of calcination. When free lime reacts with moisture or carbon dioxide gas in air, the chemical reaction produces calcium hydroxide and calcium carbonate, so a swift measurement is essential to prevent this from happening. In the past, the calibration method was applied to quantitative analysis of cements, but this technique had a difficulty in separating the peaks of free lime since the diffraction peaks of cement components were crowded in the analysis results. In the example below, we used a benchtop X-ray diffractometer mounted with a high-speed 1D detector to achieve swift measurement, and then applied the Rietveld method to perform quantitative analysis on the free lime in cements.