A Review on the Effect of Crumb Rubber Addition to the Rheology of Crumb Rubber Modified Bitumen

Table 2

Mixing parameters used by several Transportation Agencies (adopted from [9]).

Agency	Mixing temperature	Mixing time (min)	Crumb rubber size	Crumb rubber (%)
Ontario, Canada	180°C	45	0.5 mm to 1.0 mm. Gradation should be suitable to Type III of ASTM.	18–20%
California	190–226°C (adding CR)	45 (minimum)	2.36 mm–75 μm. Length of particle should not exceed 4.75 mm	20 ± 2%; (75% scrap tire CR and 25% high natural CR)
	190–218°C (blending)
Arizona	180–205°C (adding CR)	60 (minimum)	Type A (for chip seals): 2.36 mm–1.18 mm; Type B: 2.0 mm–75 μm	Minimum 20%
	165–190°C (blending)
Florida	168–190°C	30 (minimum)	Type A: 150 μm–300 μm; Type B: 300 μm–600 μm; Type C: 1.18 mm–300 μm	Minimum 20%