Study On Mechanical Property And Frost Damage Durability Of Glass Fiber Reinforced Cement

Glass fiber reinforced cement (GRC), is a new kind of composite material which with alkali-resistant glass fiber as reinforced material and with cement paste or cement grout as the matrix. As a new kind of composite material, GRC has been applied to various fields since its advent. However, the durability of GRC is still a main problem in engineering application.Especially, when GRC was in humid environment for long term, the alkaline environment of cement matrix can have a serious erosion to the glass fiber, which will significantly decrease the mechanical properties of GRC such as flexural strength and toughness. In view of the situation, in this paper, to delay the erosion rate of glass fiber and enhance the flexural strength and compressive strength of GRC, active mineral admixtures such as fly ash and silica fume were added into the ordinary Portland cement to reduce the alkaline environment of GRC, also, the influences of different hygrothermal environment on the mechanical properties and durability were studied.The influence of ambient humidity on the mechanical properties of GRC adding active mineral admixtures of fly ash and silica fume were investigated by determiningthe flexural strength, compressive strength and matrix pH of glass fiber reinforced cement (GRC) under different ages and different ambient humidity. The results showed that the ambient humidity has a significant effect on the flexural strength of GRC specimens with the increase of the age.The higher relative humidity is, the more flexural strength of GRC specimens reduce. When under the same humidity, the pH values of GRC adding fly ash and silica fume are lower than those of ordinary cement specimens in all the ages. It means that the mixture of fly ash and silica fume can reduce the alkalinity of cement hydration liquid phase, and then slow down the corrosion rate of fibers; the specimens with the addition of fly ash and silica fume were 40% and 10% performed better than the specimens with the addition of fly ash and silica fume were 20% and 10% after high temperature and high humidity accelerated aging in flexural strength an compressive strength. So it can significantly improve the mechanical properties and durability of GRC by replacing the ordinary Portland cement with 40% fly ash addition and 10% silica fume addition.To make the GRC widely used, the anti-frost property of GRC in cold regions was studied. It didn't show good performance in anti-frost property for the GRC specimens with the addition of fly ash and silica were 40% and 10%,but it still meet the requirement of frost resistance after 300 times freeze-thaw cycles,also it showed good extended durability in the long-term aging performance.