Mechanistic impacts of long-term gamma irradiation on physicochemical, structural, and mechanical stabilities of radiation-responsive geopolymer pastes

摘要

The mechanistic effects of long-term. irradiation on the mineralogical, microstructural, structural, physical, and chemical properties of 40 wt% blast furnace slag + 60 wt% fly ash geopolymer pastes have been examined. Ambient curing for 28 days during normal equilibration was followed by exposure to Co-60 irradiation (1574, 4822, 10,214 kGy). The material characteristics are controlled largely through the competing mechanisms of beneficial equilibration at initial lower dosages, which enhances gelation and crosslinking, and detrimental equilibration at subsequent higher dosages, which causes structural and microstructural destabilisation. Irradiation for 2 months (1574 kGy) increases the compressive strength similar to 45% (similar to 57 to similar to 83 MPa) through conversion of less-crosslinked (Q(0)/Q(1)/Q(1)') to more-crosslinked (Q(2)/Q(3)/Q(4)) silicate species. The transition between these regimes occurs after similar to 5 months of irradiation (similar to 4000 kGy). Beyond this, the rates of beneficial equilibration and detrimental equilibration equalise upon completion of normal geopolymerisation. Additional geopolymerisation from gamma irradiation is controlled by the rate-limiting release of Si4+ from the unreacted aluminosilicates and silicates and their rapid incorporation in the geopolymer network. The aqueous leaching of the geopolymer pastes is not affected significantly by gamma irradiation. These data reveal the potential for these materials as intermediate-level wasteforms that can outperform Portland cement-based materials.