Study On The Effects Of Polypropylene Fibers Cellulose Fibers On The Performance Of Lining Concrete

With the rapid development of the tunnel engineering in the worldwide,in the construction of the current highway tunnel,the dry lining method is still widely used in the construction of the primary lining shotcrete,or the wet concrete is designed according to the design.The wet-jet high-performance concrete has the advantages of rapid development of early strength,high strength in late stage and good construction work,which is of great significance to the current project organization.Therefore,it is very important to solve the problem of high performance concrete mix design.Tunnel lining concrete cracking and seepage is the most serious diseases affect the sound operation of the tunnel.Cellulose fibre as a new generation of high-tech materials,has a high elastic modulus,easy to spread,and many advantages,such as cement bond,so research in secondary lining concrete adding cellulose fiber has a great significance.Based on the above problems,this paper carries out the following tests:(1)Test by using silica fume,ground slag,and other mineral admixtures,high performance water-reducing agent,alkali-free accelerator and adding fiber technology,the use of suitable sand and control of water-cement ratio,slump configuration good work performance,high compactness,no cracks,transition and interface structure has been improved,high strength and resilience of small,high-performance sprayed concrete.(2)This paper in the second lining concrete adding cellulose fiber and double mixing fly ash and mineral powder to study the workability of the lining concrete,the early crack resistance,the basic mechanical properties,and permeability antifreeze performance.On the premise of adding cellulose fiber,compared the double mixing fly ash and mineral powder and the performance of the single mixing fly ash concrete.And through the above experiment it is concluded that the optimum content of cellulose fiber.By the experimental results show that:(1)Using super plasticizer,silica fume,ground slag powder admixture can increase the strength of concrete and density;the use of new liquid alkali-free accelerator,under the premise of accurate control of water-cement ratio,the better meet the performance requirements,reduce late strength loss;shot Crete adding polypropylene fibers to improve the sprayed concrete lining impermeability,frost resistance,crack resistance,improve the integrity and durability.(2)Adding fly ash and mineral powder of fiber and mixed than adding fibers and single mixing fly ash can more effectively improve the lining concrete early crack resistance,tensile splitting strength,freezing-thawing resisting circulation and permeability performance,the harm of tunnel with two lining concrete has great effect,and according to the data from optimum fiber content is 1.2 kg/m3 after.But adding fiber,double mixing fly ash and mineral powder to a certain extent reduce the workability of concrete compressive strength of the effect is not obvious,to early to bigger contribution to the late compressive strength.Through the use of polypropylene fiber concrete,cellulose fiber reinforced concrete related to the tunnel engineering test,confirmed the application effect is good.