Carbon emission factors of materials.

Due to the depletion of natural sand and gravel resources and increasing environmental restrictions, the utilization of recycled asphalt pavement materials (RAP) has become a critical approach to mitigate the consumption of natural aggregates and reduce carbon emissions in highway construction. The performance of RAP-containing asphalt mixtures is closely associated with the properties of asphalt mastic, which consists of fine RAP (FRAP), fine natural aggregates, mineral filler, and asphalt binder. However, the interactions among these components, namely fine aggregate gradation (calculated via K value), mineral filler–binder ratio, and FRAP–fine aggregate ratio, are not yet fully understood, limiting the informed design of asphalt mastic. This study aims to investigate the compositional characteristics of asphalt mastic and propose an optimized gradation suitable for engineering applications. The results indicate that an asphalt mastic with a mineral filler–binder ratio of 1.4, a FRAP–fine aggregate ratio of 50:50, and a K value of 0.65 achieves optimal overall mechanical performance. An analysis of variance shows that the mineral filler–binder ratio is the dominant factor affecting mastic performance (p K value is comparatively weak. Building on these optimized mastic parameters, the effect of the coarse aggregate-to-asphalt mastic ratio was evaluated, with a ratio of 75:25 providing the most balanced mixture performance. Compared with the standard gradation, mixtures designed with the recommended gradation exhibited approximately 35% higher dynamic stability and 28% higher fracture toughness, indicating significantly improved resistance to rutting and cracking.受天然砂石资源枯竭与环保约束日益趋严的影响，再生沥青路面材料（RAP）的资源化利用已成为缓解公路建设中天然集料消耗、降低碳排放的关键路径。含RAP的沥青混合料性能与沥青胶浆（asphalt mastic）的特性密切相关，而沥青胶浆由细粒再生沥青路面材料（FRAP）、细粒天然集料、矿粉及沥青结合料组成。然而，上述组分间的相互作用机制尚未完全阐明——包括细集料级配（通过K值计算得到）、矿粉-沥青结合料配比以及FRAP-细集料配比，这一局限制约了沥青胶浆的科学化设计。本研究旨在探究沥青胶浆的组成特性，并提出适配工程应用的优化级配方案。研究结果表明，当矿粉-沥青结合料配比为1.4、FRAP-细集料配比为50:50、K值为0.65时，沥青胶浆的综合力学性能最优。方差分析结果显示，矿粉-沥青结合料配比是影响胶浆性能的主导因素（p<0.05），而K值的影响相对较弱。基于上述优化后的胶浆参数，本研究进一步评估了粗集料-沥青胶浆配比对混合料性能的影响，结果显示当配比为75:25时，混合料的综合性能最为均衡。与标准级配方案相比，采用推荐级配设计的混合料动稳定度提升约35%、断裂韧性提升约28%，其抗车辙与抗开裂性能均得到显著改善。