A novel environmentally-friendly filler of the asphalt mastic: Organic modified waste shells

The shell farming industry generates significant waste shells annually, often improperly disposed of, causing environmental pollution. Concurrently, pavement engineering faces a shortage of limestone resources. Utilizing waste shells as a substitute for limestone fillers could simultaneously address both environmental and resource challenges. To analyze the feasibility of this strategy, this work collected the mussel, pectinid, oncomelania and oyster as the raw materials, and the method of organic modification was adopted on these shells to enhance the compatibility between the filler and asphalt. Asphalt. The physical and rheological properties of the prepared asphalt mastics were evaluated, and the modification effect was determined by the contact angle test and the surface energy parameters. Results indicated that the asphalt mastics with modified shells had higher penetration and ductility while lower softening point compared to the mastics with unmodified shells. Moreover, the modification with aluminate coupling agent had more significant impact on the physical properties of the asphalt mastics than that using amino silicone oil. For the rheological properties, shell asphalt mastics exhibited an extremely complex rheological behavior due to the various polarity and the organic content of the shell fillers. Besides, the contact angle of the shells increased after the modification, implying a better compatibility with asphalt. Moreover, the results of the surface energy parameters indicated that the non-polar component of the shells increased obvious after modification. In comparison with the conventional limestone, it can be found that the modified shells enhanced the adhesion between the aggregates and the asphalt mastics, which can improve the resistance of asphalt mixture to water damage. This work verifies the feasibility to replace the conventional mineral filler with modified shell filler, which was beneficial to recycling the waste shell and reducing the consumption of non-renewable mineral resources.