Limited effect of diameter of fibres on spalling protection of concrete in fire: Fid-Bau Portal

Limited effect of diameter of fibres on spalling protection of concrete in fire

Heo, Young-Sun / Sanjayan, Jay G. / Han, Cheon-Goo / Han, Min-Cheol

Abstract This study investigates the effect of diameter, length and melting point of fibres on spalling protection of concrete in fire. Three different diameters (0.012, 0.02 and 0.04 mm), three different lengths (9, 12 and 19 mm) and two different types (nylon and polypropylene) of fibres were investigated. Fibre volume (v%) or fibre weight per unit volume of concrete are commonly used parameters for fibre addition, but are dependent parameters on diameter of fibres. This study reports a better parameter for the expression of fibre addition which is independent of diameter, namely, number of fibres per cubic centimeter (N). When 12 mm length polypropylene fibre addition is expressed by v%, the minimum requirement for spalling protection is v = 0.20% for 0.04 mm diameter fibres and v = 0.05% for 0.02 mm diameter fibres. If the fibre addition is expressed in N, the minimum requirement is N = 133/$ cm^{3} $ for both cases regardless of fibre diameter. Hence, the diameter of fibres has limited effect on spalling protection of concrete. If the fibre addition is expressed in v%, the diameter seems to have an effect due to the fact that parameter v% is a function of diameter. In addition, increasing the length of fibres has the effect of reducing the required N for spalling protection. When fibre length is increased from 12 to 19 mm, the minimum requirement is reduced from N = 133 to 42/$ cm^{3} $. The melting point of the fibres also has an influence on spalling protection, which is discussed in detail by comparing nylon and polypropylene fibre results.