Physicochemical properties of enzymatic hydrolysis lignin-modified bitumen and its modification mechanism

Enzymatic hydrolysis lignin (EHL) is a renewable, inexpensive and widely available biomass resource, which has great potentials in improving service performance of bituminous pavement. To develop EHL-modified bitumen and to reveal modification and anti-ageing mechanisms of EHL on bitumen, the impacts of EHL on basic performance, rheological property, micromorphology, chemical compositions, molecular weight distributions and thermal decomposition behaviors of bitumen were studied using basic property tests, dynamic shear rheometer (DSR) test, bending beam rheometer (BBR) test, environmental scanning electron microscope (ESEM) test, Fourier transform infrared spectrometry (FTIR) test, gel permeation chromatography (GPC) test and thermal gravimetric analyzer (TG) test. Results show that bituminous ductility and penetration are decreased, but bituminous viscosity and softening point are increased. Bituminous deformation resistance is improved by EHL. Bituminous cracking resistance is decreased slightly by EHL. Also, the compatibility between EHL and bitumen is satisfactory. Bituminous ageing is delayed owing to abundant phenol hydroxyl groups in EHL, which capture active free radicals produced in bituminous ageing process. Moreover, EHL cross-links with asphaltene to form macromolecular network structures to lower bituminous temperature sensitivity. Finally, EHL dosage of 8% is proposed to prepare EHL-modified bitumen, which effectively reduces energy consumption and increases ecological benefits.