Development of magnesium oxalate cements with recycled portland cement paste

2020-10-23
İçınsel, Nesim
In search of lower-carbon-footprint alternatives to portland cement systems, magnesium-based cements are one of the most promising materials to investigate. Even though it is not possible to directly replace the calcium oxide in portland cement with magnesium oxide, magnesium oxide has its distinct mechanisms of forming binders with various materials. Some of the proven magnesium cements use acid-base reactions to create a binder by coupling an acid with magnesium oxide, such as the well-known magnesium phosphate cements. In this study, oxalic acid (an acid that can even be produced from carbon dioxide in the atmosphere) is coupled with magnesium oxide to form a cementitious system. In an effort to control this very reactive system, oxalic acid is blended with recycled portland cement paste. The development of an appropriate mixture design is attempted, and some experiments are carried out to investigate the possibility of forming a stable and serviceable binder. Then the developed binder (magnesium oxalate hydrate) is analyzed to elucidate the mechanism of formation and effects of raw materials, retarders, pozzolans, and mix design on the resulting system. The compressive strength development of the mortars is evaluated together with their mineralogy and microstructures using x-ray diffractometry, x-ray fluorescence spectroscopy, electron microscopy, and thermogravimetric analysis. A somewhat porous mortar, with low-to-medium strength but with a significantly lower carbon footprint than portland cement mortar could be obtained.

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Citation Formats
N. İçınsel, “Development of magnesium oxalate cements with recycled portland cement paste,” M.S. - Master of Science, Middle East Technical University, 2020.