Influence of compaction degree on the strength of asphalt mixtures and corresponding evolution model

To elucidate the mechanism of strength development in asphalt mixtures during compaction, this study selected stone mastic asphalt (SMA) as the research object. The compaction process was disintegrated into five different compaction stages based on superpave gyratory compaction (SGC) and Marshall impact compaction (MIC) methods. The uniaxial compressive (UC) strength, indirect tensile (IDT) strength and uniaxial penetration (UP) strength under various compaction degrees were obtained. Through comparative analysis, the study identified the strength evolution patterns of SMA mixtures under two compaction methods, established a quantitative relationship between the compaction degree and strength, and subsequently proposed a strength evolution model tailored for SMA mixtures. The findings indicated that there was an obvious power function increasing relationship between the compaction degree and the strength of SMA mixtures. Compaction minimally affects strength initially but significantly in later stages. The UP strength increased the most, while the IDT strength increased the least during compaction. Repeated experiments demonstrated that the strength evolution model proposed in this study exhibits high accuracy under two compaction methods, two SMA gradations and all three loading modes. The results can provide the theoretical and scientific basis for revealing the strength formation characteristics of SMA mixture.