| Concrete is the most common building materials at present. Because concrete has a lot ofshortcomings with large contraction, low tensile strength and being prone to cracks that ledto phenomenon of concrete cracking and water seepage, seriously affecting the Mechanicalproperties of concrete and durability. Due to the addition of fiber can improve the mechanicalproperties and durability of concrete, addition of fiber reinforced concrete to get the attentionof the project researchers. When fiber is added into concrete matrix, mechanical properties, wearresistances and durability of cement-based concrete could be improved, because of this, more andmore research personnel’s attention is attracted by fiber reinforced concrete. The concrete is aheterogeneous compound material, when some single material is mixed; some performances ofconcrete are improved. But such enhancement of the performance is based on a specific level, andthe multi-phase and multi-level performance of concrete is not improved comprehensively. This isthe reason of its limitation. If the overall performance of the concrete wants to be enhanced withgreater degree, the added fiber is also multi-level, so hybrid fiber concrete is formed.This thesis centering on the goal of improving the mechanical properties and impermeability ofconcrete, aiming at the plain concrete, polypropylene fiber reinforced concrete, steel fiber reinforcedconcrete and hybrid fiber reinforced concrete, passing through experimental research and theoreticalanalysis and combining with some aspects’ consideration about economy on adding different type offiber to enhance the mechanical properties of ordinary concrete and impermeability. and explore theconfounding effect of different fiber and its enhanced mechanism. The test result showed that:（1） When the fiber is mixed in concrete, the slump values of concrete decrease in varyingdegrees. Steel fiber has more significant impact on slump of concrete than polypropylene fibers. Theslump of concrete is impacted by the factor of steel fiber and polypropylene fiber. And concreteslump regression equation is Z=64.93-535875.44X2.45-15011.36Y1.34-61177400.00X2.45Y1.34（2）Analysis by the confounding effects, polypropylene fibers has more significant impact on Compressive strength than steel fibers. The compressive strength is impacted by the factors of the steel fiber and polypropylene fiber.And Concrete compressive strength regression equationis Z=（33.13-1767.50X+23355.79Y-6935500Y2+251581000Y3）/（1-62.20X-151.44X2+46554.33X3 +687.24Y-168731.86Y2）（3）Found by the impermeability of hybrid fiber reinforced concrete, polypropylene fibers hasmore significant impact on impermeability than Steel fibers. With polypropylene fiber contentincreases, the impermeability of the hybrid fiber reinforced concrete is gradually improving. Steelfiber reinforced concrete impermeability performance. With the increase of steel fiber, hybrid fiberreinforced concrete impermeability improved, but compared to plain concrete to improve grades wasnot significant. The recommended volume content of0.5%steel fiber and0.3%polypropylenefiber mixed concrete resistance performance is better.（4） By the study of Permeability of the fiber reinforced concrete tunnel lining under the waterpressure，find that concrete with fiber can improve the deformationproperties ofconcretemeasuredbystrain.Strain of concrete has a linear relationship with water pressure. And by trial can find that in the existing waterpressure test case, the concrete material in the elasticstage. And By observing the water leakage is not areflection of the inhibitoryeffect of steelfiberreinforcedconcrete dinternalcracks. |
