Ca 3 SiO5   Tricalcium silicate : C3S or TCS

HATRURITE is the mineral having the same chemical composition as Ca 3 SiO5. It is found in the hatrurim formation ( Israel)

Chemical composition :

Table 1

The maximum content of minor elements found in TCS is shown in table 2

Table 2

Mineralogical composition :

On being heated, pure Ca 3 SiO5 undergoes a series of reversible phase transitions :
620° C - 920°C - 980°C - 990°C - 1060°C - 1070°C
T1 <-> T2 <-> T3 <-> M1 <-> M3 <-> R
(T=triclinic, M=monoclinic, R=rhomboedral)

The structural differences between the polymorphs affect the coordination of Ca2+ ions and the O atoms of
the SIO 4 4- tetraedra. The pure compound, when cooled rapidly to room temperature is T1 It is possible to stabilize the polymorphic form by introducing minor element in the structure Ca 3 SiO5 is stable up to 2070°C where it melts incongruently. On equilibrium cooling, below 1250°C, Ca 3 SiO5decomposes to give Ca 2 SiO4 and CaO by a slow process. The figure 1 shows the XRD pattern for   T1  Ca 3 SiO5    

Figure 1
XRD diagram of Triclinic Ca 3 SiO5

The figure 2 shows the XRD pattern of M1  stabilized by MgO and AI2O3)
Figure 2
XRD diagram of monoclinic Ca 3 SiO5