Early age hydration and application of blended magnesium potassium phosphate cements for reduced corrosion of reactive metals

Magnesium potassium phosphate cements (MKPC) were investigated to determine their efficacy towards retardation of reactive uranium metal corrosion. Optimised low-water content, fly ash (FA) and blast furnace slag (BFS) blended MKPC formulations were developed and their fluidity, hydration behaviour, strength and phase assemblage investigated. In-situ time resolved synchrotron powder X-ray diffraction was used to detail the early age (~60 h) phase assemblage development and hydration kinetics, where the inclusion of BFS was observed to delay the formation of struvite-K by ~14 h compared to FA addition (~2 h). All samples set within this period, suggesting the possible formation of a poorly crystalline binding phase prior to struvite-K crystallisation. Long-term corrosion trials using metallic uranium indicated that MKPC systems are capable of limiting uranium corrosion rates (reduced by half), when compared to a UK nuclear industry grout, which highlights their potential application radioactive waste immobilisation. [Display omitted] •Magnesium potassium phosphate cements were studied for nuclear waste encapsulation.•The optimised formulation in this study was determined to be 0.24 w/s ratio.•Different reaction kinetics were discovered for the FA/MKPC and BFS/MKPC binders.•Struvite-K was the only crystalline reaction product observed via in-situ SXPD.•Uranium trials revealed MKPC corrosion was reduced compared to a UK nuclear grout.