Mechanical treated natural kapok fiber with Ep through oil-milling process for bio-based modified asphalt: Analysis of ageing resistance and Ep releasing

Bio-based asphalt will be used for potential sustainable and low-carbon engineering applications, and bio asphalt's ageing resistance is still a critical factor in their research and application. Kapok fiber (KF) comes from nature and has a high global production as an excellent renewable resource. Kapok fiber-modified asphalt not only optimizes the performance of asphalt but also has significant economic advantages compared to traditional modified additives. In recent works, fiber-modified asphalt has good physical properties and application performance, but its ageing resistance performance still needs improvement, as well as nature fiber-modified asphalt. This work uses ethyl parahydroxybenzoate (Ep) as a free radical receptor to improve ageing resistance in bio-based asphalt. It also uses oil-milled modified fibers as additives to enhance asphalt performance. After kapok fiber and Ep were synergistically oil-milled in engine oil (EO) preparing milled kapok fiber (OKE), bio-based asphalt (OKEA) was finally prepared by hot-mixing asphalt and OKE. From the fitting simulation of FTIR, the carbonyl contents under the short-term ageing of OKEA decreased by 50.9 % compared to OKUA (hot-mixing asphalt and only oil-milled kapok fiber). Based on elastic modulus data, the long-term ageing ratios of OKEA decreased by 12.77 %, but KEA (hot-mixing asphalt, kapok fiber, and Ep) increased by 151.8 %. OKEA decreased by 36.04 %, but KEA increased by 16.5 % in depth data, and OKEA decreased by 57.89 % but KEA increased by 36.32 % in hardness data. The release of Ep might greatly affect the ageing resistance of modified asphalt. Also, after immersing in solutions about 80 days, the decreased ratios of OKEA were 41.47 % in acetic acid solution, 29.17 % in calcium hydroxide solution, and 84.65 % in salt aqueous solution. It would help prepare new bio-asphalt with ageing resistance improvement for highly durable asphalts.