Comparative Study Between Geopolymer and Cement Waste Forms for Solidification of Corrosive Sludge

Two waste forms, namely cement and geopolymer, were investigated and tested in this study to solidify the corrosive sludge generated from the surface and precipitates of the tubes of steam generators in nuclear power plants. The compressive strength of the cement waste form cured for 28 days was inversely proportional to waste loading (24.4 MPa for 0wt% to 2.7 MPa for 60wt%). The corrosive sludge absorbed the free water in the hydration reaction to decrease the cementation reaction. When the corrosive sludge waste loading increased to 60wt%, the cement waste form showed decreased compressive strength (2.7 MPa), which did not satisfy the acceptance criteria of the repository (3.45 MPa). Meanwhile, the compressive strength of the geopolymer waste form cured for 7 days was proportional to waste loading (23.6 MPa for 0wt% to 31.9 MPa for 40wt%). The corrosive sludge absorbed the free water in the geopolymer when the water content decreased, such that a compact geopolymer structure could be obtained. Consequently, the geopolymer waste forms generally showed higher compressive strengths than cement waste forms.