Assessment Of Steel Fiber Distribution In Concrete Matrix And Its Effect On Toughness

Fiber-cement composites have gained considerable attention in building and construction markets worldwide. Fibers in cementitious matrix are effective in improving mechanical performance and toughness through resisting the emergence and development of the interal cracks. The reinforcing ability of fibers directly depends on the level of fiber dispersion throughout the material. To monitor and assess the fiber distribution is of great significance to evaluate the performance of fiber reinforced concrete.Inductive method was used as an effective tool for nondestructively assessing fiber dispersion in hardening steel fiber reinforced concrete (SFRC) and reactive powder concrete (RPC). Barcelona test and bending test were conducted to study the toughness of SFRC. Steel fibers distribution in rectangular sections was analysed based on image analysis through matlab program. The main concents are as following:(1) Calculation test were carried out firstly to discuss the the feasibility of inductive method. The total inductance increment of three main axes measured by inductive method holds linearly proportional to the fibre content, and it is viable to measure steel dosage. Besides, the inductance proportion can characterize the percentage of fibers aligned with the main axes.(2) Barcelona test was conducted to evaluate the post-cracking behavior and toughness of the cubic specimen under different directions. SFRC is anisotropy and performs different mechanical performance with different loading direction. According to fibers effect to reduce crack development, the fiber orientation efficiency could be deduced by toughness parameters.(3) The percentage of fibers in each direction estimated by inductive method and Barcelona teat were regared as two unit vectors. Vector similarity was validated by cosine ratio. A high vector similarity was obtained. And a good correlation was observed between both methods, indicating that the two methods can be validated by each other.(4) Fiber distribution in beam cross-section was analysed by Matlab program based on image analysis. Flexural toughness is closely related with total fiber number, fiber distance and fiber orientation number. Meanwhile, the toughness index prediction formulas which take the fiber distribution factors into consideration were proposed.(5) Proportion of raw materials on the mechanical strength of Reactive powder concrete was investgated.RPC with compressive and flexural strength up to 134.8 MPa and 77.3 MPa was prepared. The matrix of RPC is uniform and dense, because coarse aggregate is eliminated. Besides, steel fiber distribution in RPC is nearly uniform with great fiber content.