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<p>In heavily trafficked pavements, granite aggregates exhibit poor adhesion with acidic bitumen due to the high quartz and K-feldspar content, causing moisture damage, rutting, and reduced durability. While hydrated lime has been widely studied, its dosage has not been defined based on material-specific properties, particularly for granite and acidic binders. This study develops a novel framework to optimize lime dosage using granite mineralogy, bitumen stiffness, and traffic loading, enhancing moisture resistance, shear performance, and elasticity. Seven granites from the Ugandan Precambrian basement and two acidic bitumens (60/70 and 80/100 penetration) were analyzed. Aggregate mineralogy was determined by X-ray diffraction (XRD) and X-ray fluorescence (XRF), and classified using the Quartz—Alkali feldspar—Plagioclase—Feldspathoid (QAPF) diagram. Local hydrated lime (0–3% w/w of aggregate) was directly incorporated into hot bitumen. Moisture resistance was assessed using the indirect tensile strength test, high-temperature performance by Multiple Stress Creep Recovery (MSCR), and hydrated lime–bitumen chemical interactions by Fourier Transform Infrared spectroscopy (FTIR-ATR). Results showed a strong positive correlation between granite quartz + K-feldspar content and Hydrated Lime (HL) dosage needed to mitigate moisture damage. MSCR and FTIR confirmed that lime dosages of 0.5–2.0% improved shear resistance, elastic recovery, and progressively neutralized bitumen carbonyl and hydroxyl groups. Recommended lime dosages were refined based on binder stiffness and expected traffic (ESAL), providing a rational, adaptable approach for durable pavement design. Limitations include constant plagioclase content among samples. Future work should explore diverse mineralogies, advanced moisture testing, and field validation. This framework supports transportation geotechnics by linking aggregate mineralogy, binder chemistry, and traffic loading to resilient pavements.</p>

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Granite Mineralogy–Bitumen Acidity Framework for Hydrated Lime Optimization to Enhance Asphalt Durability and Performance

  • 期刊论文

  • 发表日期：

    2026年3月2日

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  • David Ssebitosi,
  • Hidaya Namakula,
  • Joseph Tusubira,
  • May Namutebi,
  • Umaru Bagampadde

摘要

In heavily trafficked pavements, granite aggregates exhibit poor adhesion with acidic bitumen due to the high quartz and K-feldspar content, causing moisture damage, rutting, and reduced durability. While hydrated lime has been widely studied, its dosage has not been defined based on material-specific properties, particularly for granite and acidic binders. This study develops a novel framework to optimize lime dosage using granite mineralogy, bitumen stiffness, and traffic loading, enhancing moisture resistance, shear performance, and elasticity. Seven granites from the Ugandan Precambrian basement and two acidic bitumens (60/70 and 80/100 penetration) were analyzed. Aggregate mineralogy was determined by X-ray diffraction (XRD) and X-ray fluorescence (XRF), and classified using the Quartz—Alkali feldspar—Plagioclase—Feldspathoid (QAPF) diagram. Local hydrated lime (0–3% w/w of aggregate) was directly incorporated into hot bitumen. Moisture resistance was assessed using the indirect tensile strength test, high-temperature performance by Multiple Stress Creep Recovery (MSCR), and hydrated lime–bitumen chemical interactions by Fourier Transform Infrared spectroscopy (FTIR-ATR). Results showed a strong positive correlation between granite quartz + K-feldspar content and Hydrated Lime (HL) dosage needed to mitigate moisture damage. MSCR and FTIR confirmed that lime dosages of 0.5–2.0% improved shear resistance, elastic recovery, and progressively neutralized bitumen carbonyl and hydroxyl groups. Recommended lime dosages were refined based on binder stiffness and expected traffic (ESAL), providing a rational, adaptable approach for durable pavement design. Limitations include constant plagioclase content among samples. Future work should explore diverse mineralogies, advanced moisture testing, and field validation. This framework supports transportation geotechnics by linking aggregate mineralogy, binder chemistry, and traffic loading to resilient pavements.