Effect of the oxygen concentration on the combustion of asphalt binder

The combustion mechanism and gaseous products of asphalt binder at five different oxygen concentrations (21%, 18%, 15%, 12%, and 10%) were studied by thermogravimetry-Fourier transform infrared spectroscopy (TGFTIR). The evolution of the functional groups and microscopic morphology of condensed phase were also analyzed by infrared spectroscopy (IR) and scanning electron microscopy (SEM). The semi quantitative research was realized by calculating the absorption peak area of IR, proximate and ultimate analyses. Results show that the oxygen concentration influences both the pyrolysis and combustion stages of asphalt, and the influence on the combustion of heavy components is more significant. With the decrease of oxygen concentration, the residual mass after the combustion of asphalt binder increases. Additionally, the temperature zone of combustion shifts higher, and a thermal reaction lag effect becomes more obvious. The concentration of oxygen only changes the concentration of gaseous products, instead of the types. Moreover, the concentrations of CO2, CO, H2O, SO2, etc. all decrease, and there is the biggest drop in CO2. The low oxygen concentration inhibits the dehydrogenation reaction of asphalt in the aerobic pyrolysis stage, while the complete combustion of asphalt residues is inhibited in the combustion of heavy components stage. These will all provide more scientific basis for the analysis of asphalt combustion under low oxygen conditions in tunnel fires.

采用热重 - 傅里叶变换红外光谱（TG - FTIR）研究了五种不同氧浓度（21%、18%、15%、12%和10%）下沥青结合料的燃烧机理和气态产物。还通过红外光谱（IR）和扫描电子显微镜（SEM）分析了凝聚相官能团的演变和微观形态。通过计算红外吸收峰面积、工业分析和元素分析实现了半定量研究。结果表明，氧浓度对沥青的热解和燃烧阶段均有影响，且对重组分燃烧的影响更为显著。随着氧浓度的降低，沥青结合料燃烧后的残余质量增加。此外，燃烧温度区间升高，热反应滞后效应更加明显。氧浓度仅改变气态产物的浓度，而不改变其种类。而且，CO₂、CO、H₂O、SO₂等的浓度均降低，其中CO₂的降幅最大。低氧浓度抑制了沥青在有氧热解阶段的脱氢反应，而在重组分燃烧阶段抑制了沥青残渣的完全燃烧。这些都将为隧道火灾中低氧条件下沥青燃烧的分析提供更科学的依据。