Cementation is the baseline technology for conditioning of low to
intermediate level radioactive waste. Geopolymers, a class of alkali
activated binders, are a promising new material for radioactive waste
treatment. Coal fly-ash based geopolymers are a low-cost, low greenhouse gas
footprint alternative to metakaolin based materials. Both the grouting of
sludge/powders/liquids and encapsulation of solids/compacted waste rely on
the grout maintaining optimal flow (rheological properties) during the mixing
and pouring operations, and achieving a set leading to proper long term
solidification (mechanical properties). The initial and final setting time
for fly-ash geopolymer paste, based on the SRPS EN 196-3 standard, has been
measured upon irradiation by gamma rays in a 60Co reference field positioned
with a kerma air rate of 3.42 mGys?1. The binder paste was prepared using
fly-ash from the TENT B power plant's electrostatic filters without further
sieving, activated by water glass with module 1.5 and mixed with distilled
water until a satisfactory flow was obtained, and poured into the sample and
control molds. The initial and final setting times for the irradiated sample
and non-irradiated control were determined by the Vicat apparatus. The
irradiated sample demonstrated an 11 % shorter initial setting time, and 16 %
shorter final setting time, compared to the control.