Characterization of blast furnace slag-blended Portland cement for immobilization of Co

Abstract The leaching behavior of Co2+ from blast furnace slag-blended cement is investigated. Semi-dynamic leaching test results show that the performance of the cement with regard to the retention of Co2+ is increased by replacing Portland cement with slag (~70 wt%). The changes in the formation and structure of calcium-silicate-hydrate gels in the blended cement as a function of the slag content are insignificant after 28 days of curing, while slag in the binder leads to the formation of more layered double-hydroxide (LDH) structured phases, including AFm and Co Al LDH phases. The enhanced Co uptake by the LDH phases together with the refined pore structure of the slag-blended cement significantly improves the performance for retention of Co2+ in the cement matrix.