ABSTRACT
Two reagents were used to prevent the thaumasite formation in Portland
limestone cement mortar; disodium hydrogen phosphate chelating agent and
barium hydroxide.3 and 5% of each reagent were added to the cement mortar
with 1:2 cement to sand and a w/c ratio of 0.46. The specimens were immersed
in 5% magnesium sulfate solution at 7oC up for 90 days. The compressive
strength of the cubic samples were measured at different time intervals. After 90
days exposure, the appearance of the cubic samples were inspected visually and
the phases formed were monitored by means of X-ray diffraction.
The results revealed that barium hydroxide is capable to prevent the
formation of thaumasite whilst the samples with chelating agent were
significantly damaged. The discussion is based on previous work in this field.