klinkerfasen

Klinkerfasen, or clinker phases, are the mineralogical constituents formed during the high-temperature clinkering of Portland cement. In the kiln, a mixture of limestone and aluminosilicate minerals fuses to produce nodular clinker containing several characteristic phases. The principal clinker phases are alite (tricalcium silicate, C3S), belite (dicalcium silicate, C2S), tricalcium aluminate (C3A), and tetracalcium aluminoferrite (C4AF). Typical mass fractions in ordinary Portland cement clinker are approximately C3S 50–70%, C2S 15–30%, C3A 5–15%, and C4AF 5–10%, though composition varies with raw materials and process conditions.

Each phase contributes differently to cement hydration and performance. C3S hydrates rapidly and provides early strength; C2S hydrates more slowly, contributing to strength at later ages. C3A hydrates quickly and forms ettringite in the presence of gypsum, influencing setting heat and early strength; excessive C3A reduces sulfate resistance. C4AF has a minor role in hydration but influences color and contributes to the formation of some hydrates in the early stages. The proportion and distribution of clinker phases are controlled by raw-material chemistry, kiln temperature, and cooling rate, and are routinely assessed by mineralogical analyses such as X-ray diffraction.

The concept of klinkerfasen is primarily used in cement chemistry and materials science to relate clinker microstructure to the performance of the resulting cementitious materials. The term underscores the importance of mineralogical composition in determining setting behavior, strength development, and durability.