Reutilization of Reclaimed Asphalt Binder via Co-Pyrolysis with Rice Husk: Thermal Degradation Behaviors and Kinetic Analysis

Abstract

Realizing the utilization of reclaimed asphalt binder (RAB) and rice husk (RH) to reduce environmental pollution and expand the reutilization technique of reclaimed asphalt pavement (RAP), co-pyrolysis of RAB with RH has great potential. In this study, the co-pyrolysis behaviors, gaseous products, and kinetics were evaluated using thermogravimetric analysis and Fourier transform infrared spectroscopy (TG-FTIR). The results showed that incorporating RH into RAB improved its pyrolysis characteristics. The interactions between RAB and RH showed initial inhibition followed by subsequent promotion. The primary gaseous products formed during co-pyrolysis were aliphatic hydrocarbons, water, and carbon dioxide, along with smaller amounts of aldehydes and alcohols originating from RH pyrolysis. All average activation energy values for the blends, determined through iso-conversional methods, decreased with RH addition. The combined kinetic analysis revealed two distinct mechanisms: (1) at the lower conversion range, the pyrolysis of the blend followed a random nucleation and three-dimensional growth mechanism, while (2) at the higher conversion range, the control mechanism transitioned into three-dimensional diffusion.

Keywords: TG-FTIR analysis; co-pyrolysis; combined kinetic analysis; iso-conversional method; reclaimed asphalt binder.

Figure 1

Flowchart of the experimental procedure.

Figure 2

TG-DTG curves of samples pyrolyzed at a heating rate of 10 °C/min.

Figure 3

Deviation of experimental TG curves of blends with calculated curves using TGA data of individual samples (Equation (2)) at a heating rate of 10 °C/min.

Figure 4

Three-dimensional FTIR spectra for volatiles of RAB (A) and R7H3 (C) and two-dimensional FTIR spectra at the selected temperature of RAB (B) and R7H3 (D).

Figure 5

Linear fitting plots via three iso-conversional pathways for RAB and R7H3.

Figure 6

$E_{\alpha }$ versus $\alpha$ curves of (A) RAB and (B) R7H3 obtained using the iso-conversional methods.

Figure 7

Combined kinetic optimization results of global reaction model for (A) RAB and (B) R7H3.

Figure 8

Comparisons of normalized curves at α = 0.5 of obtained kinetic models for (A) RAB and (B) R7H3 with the theoretical mechanism models.