Critical parameters of nylon and other fibres for spalling protection of high strength concrete in fire

This study investigated various types of fibre length, fibre diameter, fibre type and fibre content on the degree of spalling of concrete in fire. Four types of fibres, namely, polypropylene, polyvinyl alcohol, cellulose and nylon with various lengths and diameters were studied. Fibre contents ranged from 0.05 to 0.15% by volume of concrete. Fire tests were conducted according to the ISO 834 standard heating curve. Results showed that when comparing all the fibres under the same fibre content levels (% volume of concrete), the nylon fibre was the most effective in protecting concrete from spalling. This is because the diameter of the nylon fibres were significantly less than the other fibres, hence there were significantly more number of nylon fibres present for the same fibre content (% volume) in concrete. Analysis revealed, regardless of the amount of fibre, the type of fibre, diameter of and length of fibre, there is a strong relationship between the total number of fibres present per unit volume, length of fibres and the degree of spalling observed. Based on this relationship, the authors established a critical minimum for total number of fibres per unit volume for spalling protection in fire.