Description:
The chemical environment of barium in Portland cement which is doped with barium nitrate was investigated using x‐ray photoelectron spectroscopy (XPS) and Fourier Transform Infrared spectroscopy (FTIR). The barium-doped cement showed tremendous increases in carbonate content over the undoped cement. An XPS sulfate signal was observed in the cement doped with 20% w/w Ba(NO3)2 but not in the 0 and 10% w/w doped cement. FTIR and XPS results lead us to believe that the barium exists as both BaSO4 and BaCO3 in the cement matrix.
Ettringite formation:
Ettringite formation was also suppressed, with setting times prolonged, in proportion to the amount of BaCO 3 added. The addition of barium as a soluble salt, such as barium nitrate, also resulted in the precipitation of BaSO 4 and BaCO 3. It was suggested that the presence of large quantities of insoluble compounds hinders OPC hydration resulting in lower non-evaporable water contents and a greater proportion of anhydrous.
Typically, when small additions of CaCO 3 are added to OPC, the rate of hydration, q max, increases due to the accelerated dissolution of C 3 S and precipitation of Ca(OH) 2, which contrasts with the decrease in q max observed in this study. Other authors have reported the inhibition of OPC hydration with BaCO 3 additions, due to the formation and presence of insoluble compounds.
