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Fibre and Concrete

The macro-synthetic fibre used for this investigation is polypropylene having the properties shown in Table 1. The fibre is slightly crimped and designed to have a star cross section area so as to enhance frictional bond with the cementing matrix over its full length.

For the purpose of this study, a concrete mix with a high slump was developed to make allowance for the reduction in slump that the addition of the fibre will create. At least 90 % of the coarse aggregate (crushed Greywacke stone) used passes through the 6 mm sieve size and retained on a 4.75 mm sieve while the fine aggregate was a natural sand (locally known as Malmesbury sand) passing through 4.75 mm sieve with a fineness modulus (FM) of 2.34. CEM I 52.5 was used as the binder. Fibre content for all mixes was kept constant at a volume of 1 %. Details of the concrete mix used is presented in Table 2. When fibres are added all at once to the concrete during mixing, they have the tendency for balling, hence the fibres were carefully added to the concrete mix until a visual uniform distribution of the fibres had been observed. The consistence of the mixes (before and after the addition of fibres) were measured using a standard slump test [18]. The slump before the addition of fibres was 160 mm and reduced to 100 mm after the addition of the fibres.

Table 1 Properties of macro-synthetic fibre [19]

Specific gravity


Modulus of elasticity

4.3 GPa



Elongation at yield

15-25 %

Tensile strength

400 MPa

Melting point

150-170 °C

Length (lf)

40 mm

Nominal diameter (df)

0.8 mm

Effective diameter (deff)

0.794 mm

Aspect ratio (lf/df)


Table 2 Concrete mix design

Material type


Cement (CEM I 52.5)


Stone (Greywacke = 6 mm)


Sand (Malmesbury)




Polypropylene fibre (1 % by volume)


Superplasticizer (0.2 % by weight of binder)


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