Study On The Structure And Properties Of Alkalineresistant Phosphate Glass Fibers For Concrete

Glass fiber reinforced concrete(GFRC) is a kind of composite that consists of concrete,the matrix, and glass fiber, the reinforcement material. The glass fiber in this composite determines the properties. However, serious problems of glass fibers used in this area include high concentration of ZrO2, high melting temperature and high costs. This paper has studied the phosphate glasses that possess low melting temperatures for alkali-resistance to investigate effects of oxides on the structure and properties, especially the chemical durability. Results show that the chemical stability does get improved with different oxides, especially for the alkaline-resistance. All in all, conclusions on the influences from various sorts of oxides are as follow:When zinc phosphate glasses are doped with aluminum oxide, the dopant will loosen glass network after which it will form P-O-Al bands to enhance the glass rigidity, raising the glass transition temperature, glass crystalline temperature. All glasses remain amorphous while the density falls down because of the smaller molecular weight of aluminum oxide than zinc oxide. However, the electronegativity of aluminum oxide is high, which will result in increase in the density of glasses and alkaline-resistance.Adding zirconium oxide to the above zinc aluminophosphate glasses will lead to formation of P-O-Zr bands that will enhance glass rigidity. The glass rigidity will get improved with large electronegativity of Zr4+ ions, giving rise to increase in chemical durability. Zirconium oxide plays the role of crystalline additive that would promote crystals’ formation in glasses. The more amount of zirconium oxide are doped in glasses, the higher the density will be, the reason being more compact glass network and larger molecular weight. glass transition temperature and glass crystalline temperature. Finally, the glass rigidity will raise glass transition temperature, while the slight increase in glass crystalline temperature is related to its effects on promotion on crystals.As for the iron phosphate glasses, when introduced with alkali-earth metal oxides(viz. MgO, CaO, SrO), they will possess shorter phosphate chains, cut by the ions from the dopants. The glass rigidity moves up with more P-O-R(R=Mg, Ca, Sr) bands showing up in glass network. They will enhance the glass rigidity, improving the glass durability. Weight losses of all glasses decline as time passed by in both alkali and acid solutions. What’s more, the rest glass samples are intact after acid corrosion while those counterparts are corroded much in the alkali solution, which means the acid-resistance is stronger than the alkaline-resistance. Results from XRD and SEM of samples after corrosion indicate that there are several crystals in them, with only a few original glasses consist crystals. Densities of all samples from three glass communities got improved by the doped oxides, while SrO enhances more than the other two. All glass transition temperatures go upwards gradually with the influence of more tight glass network, while glass crystalline temperatures go towards differently. MgO and CaO strengthen this temperature in its value, in a contrary; glasses with more SrO have lower crystalline temperature. Finally, the high temperature viscosity test shows that glass with the best alkaliresistance would be made into fibers.When introduced to the calcium iron phosphate glasses, barium oxide will cause less compact network, giving rise to small rigidity of glass network. The ability to fight against the alkali solution in glasses with BaO is weaker than those without BaO. When compared within the group of glasses with BaO, the dopant will enhance chemical durability for the sake of larger ion radius of Ba2+, exerting positive effects on glass stability. The surface of glasses corroded in acid solution changes less that those doped in alkali solution.According to results from XRD spectra, more crystals emerge in calcium iron phosphate glasses. It is the larger ionic radius that results in smaller amount of crystals, higher glass transition temperature, higher glass crystalline temperature and more stable glass. The reason why the density increases is because of the bigger molar weight of BaO. The crystals emerged in glasses may be the reason for the fluctuation of densities. During the process of erosion in acid or alkali solution, glasses’ resistance to alkali ions has been improved by the larger radius of Ba2+.Moerover, all the crystals in glasses did not have positive impact on chemical stability. Last but not least, glass with best alkali-resistance could be made into fibers.