Table 6.

The fitting results of the relationship between ρ and the N.

Equation	Steel Fibers’ Ratio	a	b	c	R2
$\rho =a{N}^2+bN+c$	0%	0.22	80.2	5670	1.00
	0.5%	0.17	161	6190	0.99
	1.0%	0.18	93.7	2000	1.00
	1.5%	0.25	66.7	672	1.00
	2.0%	0.23	34.1	703	1.00
	2.5%	0.34	−18.6	896	0.99
	3.0%	0.34	−43.4	1210	0.99