Study On The Effect Of Fiber On The Properties Of Underwater Non-dispersive Concrete

The structure of concrete is characterized by good plasticity,high strength and good durability.Its raw materials are inexpensive and can be obtained anytime,anywhere.It has a good application in underwater engineering.With the increasing of underwater engineering,the application of underwater non-dispersive concrete is more and more extensive.As underwater non-dispersive concrete is constructed and formed underwater,because of the factors such as a part of slurry is lost due to flushing and poor pore structure caused by insufficient vibration,which leads to poor mechanical and durability.Therefore,improving the mechanical properties and durability of underwater non-dispersive concrete becomes the focus of the research of underwater non-dispersive concrete.This research work provides technical support and theoretical basis for improving mechanical properties and durability of underwater non-dispersive concrete.Through a large number of experimental research and practical engineering applications,the former researchers improved the performance of underwater non-dispersive concrete from the aspects of construction technology,anti-dispersant and mix ratio according to different requirements.In this experiment,three kinds of fibers,including alkali resistant glass fiber,polypropylene fiber and basalt fiber,were added in the underwater non-dispersive concrete by adding 0.1%of the volume content.It is used to explore the effect of fiber on the performance of underwater non-dispersive concrete.At the same time,5%silica fume added to the cement quality is used as mineral admixture,studied the influence of silica fume,fiber and silica fume coupling on.Firstly,the influence of fiber and silica fume on the flow performance of new underwater non-dispersive concrete is investigated through the experiment of the collapsing degree of fresh concrete.The influence of fiber and silica fume on rheology and thixotropy of mortar is explored through the rheological test of underwater non-dispersive concrete mortar.Secondly,the influence of fiber and silica fume on the macroscopical properties of underwater non dispersive concrete is explored.Through the compressive and splitting tensile tests of underwater non dispersive concrete,the mechanism of the influence of fiber and silica fume on mechanical properties is explored.The results of early shrinkage test show that fiber can effectively improve early shrinkage of concrete and silica fume increases early shrinkage of concrete.The relative dynamic modulus,compressive strength and flexural strength of the specimens after 50 freeze-thaw cycles were tested.The results show that both fiber and silica fume can improve the frost resistance of concrete,and the coupling effect between them is better than that of single fiber or silica fume.Finally,the influence of fiber and silica fume on the microstructure of underwater non dispersive concrete is explored.The hydration products of cement were analyzed by XRD test.The results showed that adding silica fume to cement hydration and adding fibers had little effect on cement hydration products.The results show that the adhesion of inorganic fiber and concrete interface is better than that of the organic fiber,and the alkali resistant glass fiber is superior to the basalt fiber by SEM.The pore structure parameters measured by mercury intrusion test show that both fiber and silica fume can improve the pore structure,and their coupling effect is better than that of single fiber or silica fume.