Effect of polyaluminum chloride on the properties and hydration of slag-cement paste

The effect of polyaluminum chloride (PACl) on the properties and hydration of slag-cement was investigated in this research. The PACl is added into slag-cement mortar with dosages of one or two percent by mass. The compressive strength of slag-cement mortar is increased with the addition of PACl after 7 days of curing. A linear correlation between the compressive strength and porosity is found. The hydration products are mainly AFt, hydrotalcite, Portlandite and C-A-S-H in all pastes. Adding one percent of PACl reduced the amount of AFt and hydrotalcite due to the favored incorporation of Al in C-A-S-H. The cross-linking degree and mean chain length of Si/Al chain in C-A-S-H are reduced if PACl is added. The PACl accelerated slag hydration by forming multimers, which mitigated the condensation and precipitation of Al species and prevented the formation of dense layer structure. The modified surface structure of slag particles favored the dissolution of inner slag, resulting in a lower degree of polymerization and higher Al/Si ratios in C-A-S-H which promoted the reaction rate of slag.