CaOinnhold

CaOinnhold, or calcium oxide content, is the proportion of calcium oxide (CaO) by weight in a material. It is a key parameter in geology, agriculture, and cement technology because CaO contributes to alkalinity, reactivity, and buffering capacity. The CaO content is usually expressed as a percentage of the sample’s mass and is determined by chemical analysis.

Analytical methods commonly used to measure CaO include X-ray fluorescence (XRF) for direct oxide quantification, X-ray diffraction (XRD) for phase composition, and various wet chemical or instrumental techniques after dissolution of the sample. In carbonate rocks, the CaO content can be estimated from the carbonate content, since CaCO3 decomposes to CaO and CO2 upon heating; a typical conversion used is CaO ≈ 0.56 × CaCO3 on a mass basis.

Applications and typical ranges:

In cement and clinker, CaO is the dominant oxide, typically around 60–65% by weight in ordinary Portland cement, with other oxides providing silicate and aluminate phases that control hydration and strength development. In limestones and dolostones, CaO content reflects the lime (CaCO3) or dolomite (CaMg(CO3)2) content, influencing industrial processing and feedstock quality. In soils and agriculture, CaO content relates to lime availability and soil pH buffering; soils with higher CaO or lime content generally require less liming to correct acidity and supply Ca2+ to plants.

Quality considerations include sample handling, dryness, and the chosen analytical method, as CaO content can be influenced by weathering, mineralogical composition, and measurement basis.