Coexistence of calcium carbonate polymorphs in cement paste

[Rockett123]

When simulating the coexistence of aragonite and calcite, aragonite always transforms into calcite.
How can I configure the system both aragonite and calcite can coexist in the cement simulation?

[gdmiron]

@Rockett123 you can set a lower meastability constraint for aragonite or the phase you want it to be stable even though termodinamically (based on the TDB) is not predicted to be stable.

In the input system definition go to the aragonite and in the column add an amount < 0 but < than the amount of calcite in equilibrium to the Lower_KC. For example, I have 0.2 M of CaCO3 in my system and added 0.1 to Lower_KC of Aragonite :

This leads to both calcite and aragonite being stable in the calculation:

But you can see that although aragonite is in the system its logSI is -0.14 - undersaturated.

You need to know the fraction of calcite/aragonite in your system from an independent source/measurement then you can plug this into the Lower_KC value. The Lower_KC and Upper_KC are used in GEMS to simulate dissolution and precipitation kinetics (metastable states)