Papers by Keyword: Magnesium Phosphate Cement (MPC)

Abstract: Effect of different curing conditions on the mechanical properties of magnesium phosphate cement (MPC), and the water resistance of MPC was improved by adding slag, the influence of slag on component and microstructure of the hydrated product were studied in this paper. The additive amount of slag was 0% ,10% , 20%, 30% and 40% separately in the ratio of total amount of MPC. It indicates that the compressive strength and flexural strength increase by about 30%,40% when the amount of slag reaches 10% of phosphate cement, respectively , and the dissolution of some phosphate which has not reacted can be prevented when cured in water for days, it improves the pH value of the solution, so the main hydration product-MgKPO₄·6H₂O hard to be dissolved under alkaline environment resulting in the decreasing of porosity ,and the decrease of strength would be controlled.

Abstract: Magnesium phosphate cement (MPC) was modified by fly ash, silica fume and re-dispersible latex powder and the properties of modified MPC, such as fluidity, setting time and compressive strength, were tested. Based on the experimental results, the contents of 50% fly ash, 10% silica fume and 2% re-dispersible latex powder were chosen to modify MPC and the water resistance of the modified MPC was studied. The experimental results showed that the addition of fly ash prolonged the setting time and significantly increased the compressive strength of MPC. The addition of silica fume improved only the water resistance of MPC. The addition of the re-dispersible latex powder prolonged the setting time and improved the water resistance of MPC.

Abstract: The Magnesium phosphate cement was prepared from MgO and NH₄H₂PO₄. The changes of the strength, appearance and hydration products of the magnesium phosphate cement were investigated, which are soaked in sulfuric acid solution, sodium hydroxide solution, sodium sulfate solution and magnesium sulfate solution. Besides, the impermeability and salt frost resistance of magnesium phosphate cement were analyzed. The results show that magnesium phosphate cement has good resistance to sulfate erosion, especially the anti-corrosion ability of magnesium sulfate. However the alkali resistance of the magnesium phosphate cement is poor. Therefore, the magnesium phosphate cements are not appropriate to be used in alkaline environment as cementitious material. The resistance of the magnesium phosphate cement to chemical attack is closely related to the stability of the hydration product MgNH₄PO₄• 6H₂O. The magnesium phosphate cements have good impermeability and salt freezing resistance.

Abstract: Fly ash can improve the physical and mechanical properties of the magnesium phosphate cement (MPC) paste. The influence of fly ash on the strength, the mortar fluidity, the durability and the setting time of MPC paste were studied in this paper. The results show that: The function of fly ash to the MPC is as followed: physical fill, superplastic and chemical reactions; the optimal content of fly ash is about 30% by weight, and MPC with 30% fly ash has excellent mechanical property and high fluidity; the fineness of magnesia affected the mechanical properties of MPC.

Abstract: In this paper, the strength characteristics of magnesium phosphate cement (MPC) under the sub-zero temperature environment had been researched, the main factors of the strength development had been analyzed. The results show that: the MPC has high early strength under the sub-zero temperature environment, but the compressive strength dropped as the temperature decreased. The way of pre-curing the MPC for 30min at 20 could improve the strength of the MPC significantly. The strength of the MPC is influenced greatly by water-cement ratio under the sub-zero temperature environment, and the amount of the mixing water should be controlled strictly.

Abstract: The recent development of two types of environmental friendly cementitious materials, magnesium oxychloride cement and magnesium phosphate cement, at HKUST are presented. Both of them can develop high strength without heat treatment under elevated temperature, i.e. the bonding of these cementitious materials can be achieved at low temperature through chemical reaction, as opposed to fusion or sintering at high temperature. The preparation process of the two cements can not only save a lot of energy but also emit no carbon dioxide. For magnesium oxychloride cement, our research includes parametric study of the formulation, strength development, water resistance, and also identification of phase composition in the cement paste. Magnesium phosphate cement is mainly applied as rapid repair material in civil engineering. In this paper, the formulation, mechanical properties and performance in patch repair of mortar specimen including strength, bond ability to old concrete substrate, volume stability are studied.

Abstract: Magnesium phosphate cement (MPC) paste is prepared by mixing dead burned magnesia powder and potassium di-hydrogen phosphate with a proper proportion of water. The superior properties such as fast setting, high early strength, low shrinkage and good bonding makes MPC suitable for applications in rapid repair of infrastructures. However, the setting time of MPC is sometimes too fast, only taking a few minutes, which causes difficulties in manipulation. How to retard and control the setting time of MPC becomes a challenging topic in both scientific and engineering fields. It was found that the setting of MPC was greatly influenced by the reactivity of magnesia, which could be determined by a quick, accurate and convenient test method. Two kinds of magnesia, namely, high-reactivity magnesia and low-reactivity magnesia were blended in order to control the setting time of MPC. Effects of magnesia to phosphate molar ratio, blending ratio and borax addition on setting time, workability and mechanical properties of MPC cement paste were investigated. Finally, the suitable ranges of the different constitutes of MPC based repair materials with satisfied workability and strength development were proposed for the practical engineering applications.