DEVELOPMENT OF A SUSTAINABLE CONSTRUCTION BINDER: OXALATE CEMENTS

Date

2024-12-26

Author

Bilginer, Baki Aykut

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One of the most pressing needs of the construction industry is the development of a lower-carbon alternative to portland cement-based binders. This thesis investigated the development of oxalate cement, a novel acid-base cement. The basic component can be dead-burned magnesia (DBM) or industrial by-products. The acidic component is a salt of oxalic acid. The oxalate ion (C2O42-) can be made from CO2, allowing the acidic component to negate the carbon footprint of the basic component. This first-of-its-kind study investigated the ideal mixture proportions to produce magnesium oxalate cements. Attempts were then made to replace DBM, which has a high chemical and calcination-based carbon footprint, with lower-carbon basic powders, namely ground granulated blast furnace slag (GGBFS), copper slag (CS), and silica fume (SF). The mechanical property development, mineralogy, and microstructure of oxalate cements were investigated. Glushinskite, a hydrated magnesium oxalate, is identified as the main reaction product when DBM is used. Whewellite and weddellite, both hydrated calcium oxalates, are formed when GGBFS is used. Humboldtine, a hydrated iron oxalate, is observed in CS mixtures. SF is found to contribute to the system in a mainly physical way. Alternative oxalate cement mortars underwent faster but less complete reactions and showed lower resistance to water than their magnesium oxalate counterparts. For some mixtures, partial replacement of DBM yields products with superior mechanical properties and durability, leading to comparable strength and water resistance to the DBM-only samples. Hence, partial replacement is a way to produce binders with a lower carbon footprint than DBM-only mixtures.

Subject Keywords

cement, oxalate, slag, magnesia, carbon dioxide

URI

https://hdl.handle.net/11511/113336

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Graduate School of Natural and Applied Sciences, Thesis