Papers by Author: Ming Xue

Abstract: The influence of water binder ratio, content of borax and fly ash on the fluidity and strength of phosphate concrete were investigated. Results showed that the slump and slump flow of phosphate concrete improved with content of water and borax increasing. But the strength decreased, especially early strength. While the mixing amount of borax was less than 1.5% of the magnesium phosphate cement, the influence on later strength was relatively less. The fluidity decreased significantly and the cohesiveness and water retention improved while the content of fly ash was between 10% and 30%.The compressive strength increased while the content of fly ash was 10%.The better curing methods was curing in the natural conditions, the compressive increased with the age prolonged.

Abstract: To prepare the concrete of high strength and high fluidity, some important factors were investigated, namely species of phosphate, the ratio of phosphate and magnesia, the surface area of phosphate cement, fineness of sand, particle size distribution of coarse aggregate and the ratio of phosphate cement and aggregate. Results showed that the fluidity and strength of phosphate concrete prepared by KH₂PO₄ were lower than that prepared by NH₄H₂PO₄ and decreased as the ratio of P/M reduced. The surface area of phosphate cement increased from 210m²/kg to 400m²/kg, the fluidity and strength firstly increased, and then decreased. The fluidity and strength of phosphate prepared by medium sands were lower than that prepared by fine sands or super-fine sands. Fast harden and early strength phosphate concrete of high fluidity can be prepared by three kinds of coarse aggregate, namely 5～10mm, 5～20mm and 5～25mm. Besides the ratio of cement and aggregate had a significant effect on the fluidity and strength, and the best ratio fell between 1:1 and 1:2.

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: 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 porous apatite-wollastonite bioactive glass-ceramic (AW-GG) was made from nano-precursor powders derived from sol-gel process, and shaped by dipping method with polymer foam. The physical-chemical properties, bioactivity and biocompatibility of the materials were studied by means of TG, XRD, SEM, TEM and so on. The bioactivity was investigated in simulated body fluid (SBF) and the biocompatibility was evaluated by co-culturing with marrow stromal cells (MSCs). The result shows that: the particle size of the AW precursor powders is 40~100nm; porous AW GC has three-dimensional pored structure with 300~500um macropores and 2~5um micropores; the materials possess high bioactivity and biocompatibility. Porous AW GC may therefore have great potential application as bone tissue engineering scaffold.

Abstract: Merwinite powders were synthesized by a sol-gel process. The bioactivity in vitro of merwinite was investigated by soaking the powders in simulated body fluid (SBF), the growth of hydroxyapatite(HAp) on the surface of the powder was evaluated in various time. It was found that hydroxyapatite was formed after soaking for 14 days. The results indicate that merwinite possessed apatite-formation ability might be a potential candidate biomaterial for hard tissue repair.