Steel fibres: aspect ratio

Figure 12.5 Influence of steel fibre volume fraction on the workability of cement-based materials for different fibre aspect ratios /d, after Edgington etal (1974).

In the first solution, the highest values of and have been for steel fibres of volume fraction V and fibre aspect ratio L/d. In the second problem, the optimization of cost, which means minimum volume of fibres was looked for. In both problems the importance of variables was the same, that is, all variables were considered with the same weights. Numerical solutions to both problems show the utility of the proposed method for practical applications in different formulations. 

The influence of aspect ratio of steel fibres on effective shielding may be illustrated... 

Another factor that influences the value of pc is the aspect ratios of the metallic filler. Metal fibres, metal-plated glass fibers, and metal flakes can significantly lower the concentration required to achieve isotropic conduction as compared to spherical powders [3]. Values of pc as low as 1 vol % have been reported with stainless steel fibers having an aspect ratio of 750 [37]. 

Both characteristics depend on the type of fibres, their aspect ratio and tensile strength and on the fibre-matrix bond. All these factors contribute to the efficiency of the fibres, which determines the shape of the curves beyond point MOR. For steel fibres, in most cases the fibres do not break but are pulled out of the matrix. 

For preparation of specimens a basic concrete mix of following proportions was used cement 1.0, sand 0-2 mm, 2.0, aggregate 2-A mm,0.54, water, 0.5. The FRC mixes used the same matrix and comprised fibre volume contents of 1.25 t and 2.5 Straight smooth steel fibres of the aspect ratio of... 

Straight fibres produced by cutting the unraveled wire from scrap or wornout steel cables and wire ropes (S-fibre),which are much cheaper than the other two, the cost of S-fibres is approximately 50% of that of M-fibres or 30% of that of H-fibres. The aspect ratio (length to equivalent diameter) is about 50 for H-fibre and M-fibre,75 for S-fibre. To allow comparison of the properties of SFRC with different types and contents of steel fibres, the matrix of all specimens is the same for each group of tests. 

Thus, different fibre geometries and fibre-matrix interactions can affect the flexural behaviour of SFRC. This is demonstrated in Figure 7.18 [41], which shows the effects of different fibre shapes on the flexural behaviour of steel fibre shotcrete. These data suggest that the aspect ratio (//d) concept, which was developed for smooth, straight fibres, is not really useful when applied to deformed fibres,... 

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