Mechanisms associated with sulfidation gas release, desulphurisation and degradation of rubber powder in crumb rubber modified asphalt

Odorous sulphidation gases are released during the construction of crumb rubber-modified asphalt (CRMA), causing pollution to the environment. To study the associated mechanism of sulfidation gas (H2S, CH4S, COS and CS2) release and the desulphurisation and degradation of CR in asphalt, the release law of sulphidation gas of CRMA was studied by a gas detector. Gel permeation chromatography (GPC), fluorescence microscope, toluene insoluble (TI) and potentiometric titration tests were used to study the desulphurisation and degradation of CR. The results showed that vulcanised CR in CRMA led to the generation of sulphidation gas with the increase in temperature, time and stirring speed. The average molecular weight of CRMA increased, while the TI and unsaturation (A) decreased after the desulphurisation and degradation of CR. Under the influence of temperature, heating time and stirring speed, the A was reduced by 0.72%∼8.87%, 1.18%∼10.69% and 0.75%∼8.12%, respectively. There was a strong correlation between the concentration of sulphidation gas and the desulphurisation and degradation parameters of CRMA. The reaction of ·H, –CH3, CO with the –SxH generated by the C–S, S–S, C=C fracture during the desulphurisation and degradation of CR was the main reason for the generation of sulphidation gas.