Strong retarding effects were reported when phosphates or phosphoric acids were added during CAC hydration . Manninger et al. found that the addition of H 3 PO 4 led to the insertion of a retardation period before initial CA dissolution. The authors proposed that the superficial precipitation of an amorphous calcium-phosphate-phase might cause the blocking of initial CA dissolution while attributing the duration of the retardation period to the buffering ability of the acid.