Synthesis and Characterization of Calcium Alginate Capsules Encapsulating Soybean Oil for In Situ Rejuvenation of Aged Asphalt

Abstract

Asphalt aging is a major cause of distresses in asphalt pavement, seriously decreasing the in-service performance and shortening the lifetime of pavement. Traditional asphalt rejuvenating methods usually consume a great deal of worker and energy resources. This study encapsulated rejuvenator to automatically realize in-situ rejuvenation of aged asphalt in pavement. Soybean oil was selected as the asphalt rejuvenator, and its effectiveness in rejuvenating the aged asphalt was identified. Then it was encapsulated into three kinds of calcium alginate capsules by the orifice coagulation bath method. Next, the micromorphology, internal structure, density, mechanical strength, and thermal stability of the capsules were characterized using digital microscopy, stereomicroscope, graduated cylinder test, uniaxial compressive test, and thermogravimetric analysis, respectively. The effects of the capsules on the pavement performance of asphalt mixture were analyzed. Test results showed that the soybean oil effectively recovered the properties of the short-term aged asphalt binder at an optimum content of 2% by binder mass, and it was encapsulated successfully in capsules with diameters of about 2 mm. There were many slight bumps and indentations on the capsule surface, and many pores filled with soybean oil inside the capsule. The density of the capsules was close to that of the asphalt binder, providing a favorable condition for their uniform distribution in the asphalt mixture. It was proved that the capsules can resist the mechanical and thermal conditions during road construction. The pavement performance of asphalt mixture containing capsules still met the requirement of the specification in China. The findings of this paper are helpful to prolong the service life of asphalt pavement and reduce the maintenance costs in the long run, ultimately contributing to the development of smart and sustainable pavement.