Study On Durability Of Basalt Fiber-reinforced Fly Ash Concrete

To meet the fast growing requirements of the economy and quality of life, the construction industry has gotten an unprecedented prosperity in recent 30 years. Now a large number of concrete structures are entering service-maintenance period. It is shown that prohibitive expenses are spent on the maintenance and reinforcement of a lot of concrete structures due to the premature failure causing by the insufficient durability, which becomes a heavy burden on our economy construction. Therefore, it is particularly important to research on improving the durability of the concrete. This study researches on the basalt fiber-reinforced fly ash concrete, and investigates the influence of the water binder-ratio, fiber volume content and fly-ash to the mechanical properties and durability of basalt fiber-reinforced fly ash concrete by testing its mechanical properties, freeze-thaw resistance,sulfate resistance. The study indicates that:1.Using the method of equal volume fiber to replace sand, when the volume fraction of basalt fiber ranges from 0.12% to 0.30%, the fiber makes no significant effect to the compressive strength of basalt fiber-reinforced fly ash concrete. However, its flexural strength improves when increasing the volume fraction of fiber, which shows that the basalt fiber obviously improves the toughness of fly-ash concrete.2.When the total amount of cementitious material is fixed and the content of fly-ash ranges from 20% to 38%, the compressive strength of basalt fiber-reinforced fly ash concrete trend to decline with the adding of basalt fiber.3.Under the wet-drying cycles effect of 5% Na2SO4 solution with the same water-binder ratio, the flexural strength of basalt fiber-reinforced fly ash concrete increases with the increase of the volume fraction of fiber. Fly-ash has a positive effect on the sulfate resistance ability of the basalt fiber-reinforced fly ash concrete.4.Employ the quick frost method to do freeze-thaw test on basalt fiber-reinforced fly ash concrete of different contents of fly-ash. As the number of the cycle times and water-binder ratio increases, the frost resistance of concrete specimens declines. That is, the fly-ash content will influence the frost resistance of concrete.5.Use non destructive testing evaluation methodapply infrared thermal imaging technique to explore the corrosion extent of freeze-thaw damage to concrete. The evaluation of the concrete damage are divide into four grades-I, II, III, IV. The relationships between infrared thermography temperature and injury level are established based on protective layer thickness of different types of concrete structures to evaluate corrosion freezing injury level of concrete. The method is easy to use, but is sensitive to the ambient temperature and humidityof concrete.In summary, for larger density of the flexible fibers, mix design method of fiber-reinforced concrete use equal volume of fiber to replace sand, can significantly improve the flexural properties of the fly-ash concrete while it makes no obvious effect to the compressive strength of basalt fiber-reinforced fly ash concrete. It is easy for sulfate solution to corrode the concrete, the addtion of the basalt fiber and fly-ash can significantly improve the erosion resistance to the sulfate of the concrete. Nevertheless, the fly-ash will reduce the frost resistance of the concrete. Increase the content of fly-ash will notably reduce the frost resistance ability of concrete. It’s feasible to apply infrared thermal imaging technique to detect and evaluate the injury level of corroded/damaged concrete. The affecting factors need further study and discussion.