Abstract
The purpose of this study is to explore the viscoelastic properties, rutting resistance, and fatigue resistance of waste wood-based biochar-modified asphalt. The biochar with 2%, 4%, and 8% mixing amounts and two kinds of particle size, 75–150 μm and <75 μm, were used as modifiers of petroleum asphalt. Meanwhile, in the control group, a graphite modifier with a particle size of 0–75 μm and mixing amount of 4% was used for comparison. Aged asphalts were obtained in the laboratory by the Rolling Thin Film Oven (RTFO) test and the Pressure Aging Vessel (PAV) test. The viscoelastic properties, rutting resistance, and fatigue resistance of biochar-modified asphalt were evaluated by phase angle, critical high temperature, and fatigue cracking index by the Dynamic Shear Rheometer (DSR) test. In addition, the micromorphology of biochar and graphite was compared and observed by using the scanning electron microscope (SEM). The results show that increasing the mixing amount of biochar gave a higher elastic property and significantly better rutting resistance of the modified asphalt at high temperature. Compared with graphite, the biochar has a rougher surface and more pores, which provides its higher specific surface area. Therefore, it is easier to bond with asphalt to form a skeleton network structure, then forming a more stable biochar–asphalt base structure. In this way, compared to graphite-modified asphalt, biochar-modified asphalt showed better resistance to rutting at high temperature, especially for the asphalt modified with biochar of small particle size. The critical high temperature T(G*/sinδ) of 4% Gd, 4% WD, and 4% Wd was 0.31 °C, 1.57 °C, and 2.92 °C higher than that of petroleum bitumen. In addition, the biochar asphalt modified with biochar of small particle size had significantly better fatigue cracking resistance than the asphalt modified with biochar of large particle size. The fatigue cracking indexes for 2% Wd, 4% Wd, and 8% Wd were 29.20%, 7.21%, and 37.19% lower by average than those for 2% WD, 4% WD, and 8% WD at 13–37 °C. Therefore, the waste wood biochar could be used as the modifier for petroleum asphalt. After the overall consideration, the biochar-modified asphalt with 2%–4% mixing amount and particle size less than 75 μm was recommended.
Highlights
Biochar is a kind of organic compound product rich in carbon
A short-time aging test was conducted on the asphalt according to the specification AASHTO T240 [32], where the test temperature was 163 ± 0.5 ◦ C, the aging time was controlled for 85 min, the weight of the asphalt sample in the sample bottle was 35 g ± 0.5 g, and the flow rate of air injection in the oven was 4000 L/min ± 200 mL/min
The viscoelastic properties of asphalt can be evaluated by its phase angle
Summary
Biochar is a kind of organic compound product rich in carbon. It has many varieties, which is mainly produced by pyrolysis technology [1,2]. Most of the existing research on biochar has worked on the environmental science and soil science fields. The biochar plays a great role in agricultural soil improvement, environmental pollution remediation, soil carbon pool enhancement, and greenhouse gas emission reduction [3,4]. The biochar, acting as a soil modifier, can promote nutrient cycling to improve soil productivity and plant growth [5,6,7,8]. Inactivated biochar is hard to isolate from soil [9,11]. If it is piled without control, the biochar in air will serve as a threat to our human body [12]
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