Experimental Research On The Anti-crack Mechanism And Microscopic Simulation Of The Hybrid Fiber Concrete

Concrete is the world's major building materials with its integrity, lower engineering and maintenance cost ,and anti-permeability. And as building material, its performance is the key factors which could affect the use function of the structure. The poor ability of anti-cracking is always one disadvantage of concrete。There will be great significance that if we could know how to improve the concrete anti-cracking performance and then establish a corresponding enhancement model to recognize the contribution of every kind of material make for improve anti-cracking.This thesis centering on the goal of enhancing crack resistance performance of concrete, aiming at the plain concrete, polypropylene fiber reinforced concrete, steel fiber reinforced concrete and hybrid fiber reinforced concrete, through comparing by adding different amount of fiber to the plate cracking, study on the crack resistance performance between ordinary concrete and other。Through scanning electron microscopic , meso-level structure mixed with different fiber is analysisd .At the same time , the change of micro structure that fiber make on concrete is observed. Through ANSYS ,a fiber concrete model on microscopic level with random distribution is created .The role of fiber play in the process of performance enhancement is discussed.The results show that:(1) the presence of fibers makes the crack resistance of the specimens greatly improved. Crack resistance effect of hybrid fibers> Single Polypropylene> Single-doped fiber.(2) there is an optimum fiber content that can do the maximum crack resistance effect and at the same time saving materials, recommended 0.5% steel fiber, polypropylene fiber volume content of 0.1%.(3) Because the micro structure of the matrix changed, the hydration reaction could fully carry out and spatial distribution of the number and arrangement of the situation of the Ca(OH)2 crystal could be improved,this make crack resistance of the hybrid fiber reinforced concrete improve.(4) the microscopic fibers model built in ANSYS could verify the fiber's role in microstructure's changes .This provide a reference for revealing the initial mechanism of fiber reinforced concrete t.(5) use the the stress - strain curves on the tunnel model for a mechanical analysis, the results can reflect the performance of micro parameters to the macro impact.Finally, the paper summarized the work done, and briefly pointed out the shortcomings of this study.