Consequently, we can conclude that adding hydrochloric acid leads to the inhibition of the initial CA dissolution. Thus, in the presence of HCl, a dissolution-inhibition period is inserted before the first period of the conventional four periods of CAC hydration (initial dissolution, dormant period, acceleration, deceleration). This is in line with the results from Manninger et al. , who studied the influence of phosphoric acid on the hydration of CAC pastes. Similarly to our observation, the inhibition period induced by acid addition was characterized by a pH value in the neutral range and low Ca and Al concentrations in the pore solution. At the same time, the phosphorous concentration decreased after binder addition but stayed constant during the inhibition period. It was speculated that H 3 PO 4 forms amorphous compounds with Ca and Al (such as amorphous calcium phosphate and AH x ), which hinder further dissolution of CA . With hydrochloric acid, calcium chloride cannot precipitate due to its high solubility (420 g/L ), but Al(OH) 3 is expected to form. Calcium concentration continues to rise between 0 min and 35 min, albeit very slowly, while the aluminum concentration remains stable, indicative of a slow dissolution-precipitation or diffusion process. The formation of Al(OH) 3 likely reduces the CA dissolution rate: a strong decrease in a mineral dissolution rate is typically observed when the solution is close to saturation with regards to the mineral itself or to (an)other phase(s) . Here, the saturation state of the solution likely limits aluminum transport from the CA to the solution and reduces the dissolution rate . In addition, if Al(OH) 3 forms at the surface of the CA, the alumina layer may hinder the water diffusion toward the unreacted CA core, thus preventing calcium leaching. The solubility of Al(OH) 3 increases as soon as the solution saturation state decreases (i.e., above pH ∼6.25, see Figure ), and the initial CA dissolution can proceed similarly to the experiment with H 2 O.