Replacement of the Basic and Acidic Components of Magnesium Potassium Phosphate Cement with Calcium Sulphoaluminate Cement and Fly Ash Phosphate Salts

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2022-12-02

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Mazaheri Shadbad, Hossein

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Magnesium phosphate cement (MPC) is an acid-base cement with applications as a construction material. This cement has properties superior to portland cement like high early strength. However, MPC has a short setting time, high heat of hydration, and poor water resistance. In addition, this cement uses dead-burned magnesium oxide, prepared at around 1500 ˚C, which consumes much energy, releases CO2, and increases cost. In this study, the two main components of magnesium potassium phosphate cement, dead-burned MgO and potassium dihydrogen phosphate (KH2PO4) are replaced with less-expensive and environmentally-friendly materials; a calcium sulphoaluminate cement and a mixture of phosphoric acid and fly ash, in three groups of mixtures. In Group I, KH2PO4 is replaced with the fly ash phosphate, and it is observed that the setting time is shortened, but water resistance increases significantly. In Group II, MgO is replaced with calcium sulfoaluminate cement, setting time increases up to 7 hours, and early-age compressive strength is low, but similar to the reference mix at 28 d. In Group III, both components are replaced. This group has a longer setting time than Group I and shorter than Group II as well as vi lower compressive strength. Unlike in typical MPC, Reaction products of all mixtures are predominantly amorphous.

Subject Keywords

Magnesium Phosphate Cement, Acid-Base Cement, Fly ash, Phosphoric Acid, Potassium Dihydrogen Phosphate, Calcium Sulphoaluminate Cement

URI

https://hdl.handle.net/11511/101305

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

H. Mazaheri Shadbad, “Replacement of the Basic and Acidic Components of Magnesium Potassium Phosphate Cement with Calcium Sulphoaluminate Cement and Fly Ash Phosphate Salts,” M.S. - Master of Science, Middle East Technical University, 2022.