I think I found one!
I am looking for cement for AQUARIUM application.
according to the DIY rock gurus the cement ratings are as follows (for aquarium use):
Cement Types
Type I - Normal (Can be used)
Type II - Moderate Sulfate Resistance (Better than I)
Type III - High Early Strength (No point)
Type IV - Low Heat of Hydration (No Point)
Type V - High Sulfate Resistance (Best to use)
Type GU - General Use (Ok to use)
Type HE - High Early-Strength (Pointless)
Type MS - Moderate Sulfate Resistance (Better than I or GU)
Type HS - High Sulfate Resistance (Best to use)
Type MH - Moderate Heat of Hydration (Pointless)
Type LH - Low Heat of Hydration (Pointless)
Type HAC - High Alumina Content (Good/best to use)