Study On Durability Of Glass Fiber Reinforced Ordinary Portland Cement

GRC (Glass Fiber Reinforced Cement, GRC ) is a type of composite material using glass fiber to reinforce matrix or mortar. As a new type of composite material, GRC has been improved continuously since its coming out and used widely in various fields.However, there's still a problem that GRC's long-term performance especially the decrease of its toughness in damp environment has not been solved once and for all, which has become one of the main reasons that limits its usage in greater range. For many years, researchers at home and abroad, who have been devoting to the researches on the mechanism of the decrease of GRC's long-term performance and the methods for its durability improvement, have adopted many technical measures such as using low alkaline cement or ordinary Portland cement modified by using reactive admixtures.But the cost for using low alkaline cement is too high and the cement factories are rather few. And when using reactive admixtures to improve the durability of the GRC which uses ordinary silicate cement as base material , it then will cause the problem that GRC's early strength is low and the demolding time is langer.The research mainly solves the following problems: â‘ research to solve the durability problem of glass fiber reinforced ordinary Portland cement by adding mineral admixture; â‘¡research to solve the low early strength problem and demolding time is langer of glass fiber reinforced ordinary Portland cement; â‘¢ set up experimental methods and evaluation indexes suitable to evaluate the durability of glass fiber reinforced ordinary Portland cement.The research on the factors which influence GRC's durability shows that it is effective to improve the durability of glass fiber reinforced ordinary Portland cement by using reactive admixtures such as fly ash, silica fume.Among which the experiment group using 50% fly ash,10% silica fume instead of ordinary Portland cement shows rather better durability either in standard curing or the accelerated aging experiment. The quality of fly ash especially its fineness will have important influence on the long-term performance of GRC. Ground fly ash and silica fume which have great positive influence on GRC's long-term durability are important factors to improve the flexural and compressive strength in the later stage and among them the silica fume has greater contribution.Besides, the factors such as the proportions of SiO2 in the glass fiber chemical compositions, the types of glass fiber, the length of glass fiber and its volumeall have important influences on GRC's strength under the accelerated aging conditions.Under other circumstances with the same conditions, using AR glass fiber with higher TiO2 has better effects.Use hardening accelerator can improve the GRC's early strength prominently. Improving the fineness of fly ash can also improve GRC's early strength. The finer the fly ash is, the more prominent the GRC's early strength can be improved.For the strength in the first day, with the increase of Na2SO4 contents, either the flexural strength or the compressive strength improved obviously. The flexural strength of GRC with 1.5% Na2SO4 added in is 70% higher than without it and the compressive strength is at least 24% higher too. Although Na2SO4 will increase GRC's early strength, it has negative influences on the durability, namely, Na2SO4 will decrease GRC's strength in later aging.The early strength by compound using ground fly ash, silica fume and hardening accelerator can be improved much greatly than by single measures. The increase of compound measures is not simply adding the increase effects of ground fly ash and chemical activation together but higher than it.With shotcrete admixture added in, the specimens' demolding time is much shorter than the ordinary Portland cement specimens without it, and with the increase of shotcrete admixture contents, the specimens' demolding time becomes shorter and shorter. Although shotcrete admixture can shorten the demolding time greatly, it has no noticeable influences on the improvement of speci...