Blast furnace slag-Mg(OH)2 cements activated by sodium carbonate. Issue 41 (26th June 2018)

• Record Type: Journal Article
• Authors: Walling, Sam A.; Bernal, Susan A.; Gardner, Laura J.; Kinoshita, Hajime; Provis, John L.
• Is Part Of: RSC advances. Volume 8:Issue 41(2018)
• Page Start: 23101
• Page End: 23118
• Publication Date: 2018-06-26
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c8ra03717e
• Languages: English
• ISSNs: 2046-2069

Abstract

Abstract : Novel cements can contain up to 50 wt% Mg(OH)2, offering a new route to immobilisation of this nuclear waste constituent. Abstract : The structural evolution of a sodium carbonate activated slag cement blended with varying quantities of Mg(OH)2 was assessed. The main reaction products of these blended cements were a calcium-sodium aluminosilicate hydrate type gel, an Mg-Al layered double hydroxide with a hydrotalcite type structure, calcite, and a hydrous calcium aluminate phase (tentatively identified as a carbonate-containing AFm structure), in proportions which varied with Na2 O/slag ratios. Particles of Mg(OH)2 do not chemically react within these cements. Instead, Mg(OH)2 acts as a filler accelerating the hardening of sodium carbonate activated slags. Although increased Mg(OH)2 replacement reduced the compressive strength of these cements, pastes with 50 wt% Mg(OH)2 still reached strengths of ∼21 MPa. The chemical and mechanical characteristics of sodium carbonate activated slag/Mg(OH)2 cements makes them a potentially suitable matrix for encapsulation of high loadings of Mg(OH)2 -bearing wastes such as Magnox sludge.