Influence of limestone mineral powder properties on asphalt mortar performance and its technical standards

Abstract:

To investigate the main factors affecting the anti-frost properties of asphalt mortar and provide classification and selection principle for limestone powder, we carried out freezing-thawing cycle tests on asphalt mortar with different types of mineral powder. The chemical composition, microscopic morphology, microscopic mechanical property, and rheological property were detected during the freezing-thawing cycles, and random forest analysis was conducted on the test results. Results showed that the addition of mineral powder improved the anti-aging properties of asphalt mortar during freezing and thawing. After freezing-thawing cycles, the decrease in mortar roughness and the increase in surface modulus showed a downward-parabolic trend with the content of CaCO₃ (mass fraction), while the adhesion decreased linearly with the content of CaCO₃. The CaCO₃ content of mineral powder should not be less than 85%, so as to maintain the stability of asphalt mortar properties after freezing-thawing cycles. Asphalt pavement moisture damage was more likely to occur in seasonal frozen area than in non-seasonal frozen area. Compared with non-seasonal frozen area, the CaCO₃ content of mineral powder in seasonal frozen area should be increased by 10%. Random forest analysis showed that the ranking of influence factors of physical and chemical indexes of mineral powder on the properties of mortar were specific surface area (SSA) > CaCO₃ content (CC) > fineness index (X₉₀) > index of plasticity (IP). Specific surface area affected the reaction rate of asphalt and mineral powder, while CaCO₃ content affected the adequacy of the reaction. The technical requirements of limestone rocks and the comprehensive classification technical standards of mineral powder were proposed, which can guide the classification, selection, and production of mineral powder for road usage.