Water-glass as a binder is used in acid and fire-proof applications. A chemical modification influences the curing rate or characteristics like the flexural and compressive strength. The aim of this work is to investigate the influence of the addition of C3S, C3A, and Na3(PO3)3 on the chemical durability of cured sodium silicate mortars. The results show that the addition of clinker minerals as accelerator reduces chemical durability and makes these binders unusable for acid-proof applications. The addition of Na3(PO3)3 makes the sodium silicate binder durable against water and acid attacks and triples the compressive strength.