Hydraulic limes, "natural" cements, and "artificial" cements all rely upon their belite content for strength development. Source: Internet
The materials in cement clinker are alite, belite, tri-calcium aluminate, and tetra-calcium alumino ferrite. Source: Internet
The level of clay components in the limestone (around 30–35%) is such that large amounts of belite (the low-early strength, high-late strength mineral in Portland cement) are formed without the formation of excessive amounts of free lime. Source: Internet