Laboratory and onsite study of barium hydroxide as a consolidant for high porosity limestones

The paper focuses on the study of barium hydroxide applied to two high porosity limestones from Portugal (Ançã stone, with 27% porosity) and Italy (Lecce stone, with 37% porosity), both in the laboratory and onsite. The results show that barium hydroxide acts both through carbonation with atmospheric CO2 and by replacing calcium for barium in the calcite lattice followed by carbonation of the released calcium hydroxide. This double mechanism proved to be particularly efficient in the Ançã limestone, possibly due to a higher reactivity linked to its smaller grain size. The mechanism is far slower than simple carbonation and has a better outcome when the stone can be totally immersed in the solution. Onsite experiments on the Ançã stone were less striking than in the laboratory, possibly due to the insufficient amount of product made available for reaction, but a positive outcome was visible after six years of natural exposure.