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Dr. Mohammad Nahid Siddiqui Prof. Mohammad Farhat Ali & Eng. Mirza Ghouse Baig

Effect of Anti-Stripping Agents in Asphalt-Aggregate Interactions. by. Dr. Mohammad Nahid Siddiqui Prof. Mohammad Farhat Ali & Eng. Mirza Ghouse Baig. Department of Chemistry King Fahd University of Petroleum & Minerals Dhahran, 31261 Saudi Arabia. Objective.

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Dr. Mohammad Nahid Siddiqui Prof. Mohammad Farhat Ali & Eng. Mirza Ghouse Baig

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  1. Effect of Anti-Stripping Agents in Asphalt-Aggregate Interactions by Dr. Mohammad Nahid Siddiqui Prof. Mohammad Farhat Ali & Eng. Mirza Ghouse Baig Department of Chemistry King Fahd University of Petroleum & Minerals Dhahran, 31261 Saudi Arabia

  2. Objective To Study the effects of antistripping agents on asphalt-aggregate mixtures using Adsorption-desorption and IR test methods.

  3. Presentation OutLine • Introduction and Background • Moisture Damage • Anti-Stripping Additives • Experimental • Asphalt & Aggregate Properties • Adsorption-desorption Testing • Results and Discussion • Conclusions

  4. Moisture Damage Significance: A high degree of stripping was detected in between 25 to 50% on various pavement sites inspected in Saudi Arabia during late 1990.

  5. Moisture Damage Main Focus: To Improve aggregate asphalt bonding.

  6. Antistripping Additives • Organic Small Molecules • Amines, Silanes • Polyamines, Amidoamines • Inorganic Aggregate Treatments • Hydrated Lime • Portland Cement • Polymeric Agents • Functionalized Butadiene • Styrene-Butadiene

  7. Introduction & Background • Asphalt-aggregate interactions in pavements • directly affect the adhesion & bond strength. • Chemistry of asphalt & surface chemistry of • aggregates particularly affects the interactions.

  8. * Wettability * Viscosity (temp) * Composition (oxygen) * Durability *Surface chemistry (mineral composition) * Surface texture * Porosity * Surface condition (cleanliness, moisture) Asphalt-Aggregate Bonding Aggregate Asphalt

  9. Effect of Surface Film on Aggregate Coverage (after Hubbard)

  10. Effect of Aggregate Surface on Texture Adhesion (after Hubbard)

  11. Contact Angle in an Aggregate, Asphalt and Water System (after pfeiffer).

  12. Asphalt-Aggregates Bonding

  13. Effect of Polarity on Adhesion (after Hubbard)

  14. Molecular Orientation (after Hubbard)

  15. Experimental Work • Asphalts from Two Refineries • Riyadh Refinery (RY) • Ras Tanura Refinery (RT) • Aggregates from Three different regions • Taif • Eastern Province (EP) • Riyadh • Three Anti-Stripping Agents • Iterlene IN/400-S • Cecabase 260 • Polyram L200

  16. Sample ID Elements RT RY C H S N O H/C O/C (x10-3) S/C (x10-2) N/C (x10-3) Asphaltenes % Ni V V/Ni 84.25 10.14 4.99 0.41 0.21 1.43 1.87 2.22 4.19 27 97 3.59 84.66 10.41 4.58 0.39 Nil 1.46 Nil 2.03 3.96 33 114 3.45 Elemental Analysis (wt %) of RT and RY Asphalts

  17. Physical Characteristics of RT and RY Asphalts

  18. Aggregates • Limestone (Eastern Province) • Basalt (granite) (Western Province, TAIF) • Limestone (Riyadh Area)

  19. Properties of Aggregates

  20. Anti-Stripping Agents

  21. Chromatography Column

  22. Adsorption Equation Ai = [VC (A1 – A2)]/50 A1 where, Ai = initial adsorption, mg/gm V = volume of solution in the column at the time A2 is measured, ml = 00.0 ml C = initial concentration of asphalt in solution, gm/l = 1.2 g/l A1 = first absorbance reading A2 = second absorbance reading after 6.5 hours

  23. Results & Discussion: Initial and Net Adsorption Values for Riyadh Asphalt with Cesabase-260

  24. Results: (Cont’d) Initial and Net Adsorption Values for Ras-Tanura Asphalt with Cesabase-260

  25. Results: (Cont’d) Initial and Net Adsorption Values for Ras-Tanura Asphalt with Iterlene 400-S

  26. Results: (Cont’d) Typical Comparison on Riyadh asphalt-aggregate mix

  27. Results: (Cont’d) Typical Comparison on Ras Tanura asphalt-aggregate mix

  28. Conclusions Based on the results of this study following conclusions were drawn. • Type of Aggregates has significant effect on absorption behavior. • Different aggregate showed different adsorption for same asphalt. • Moisture sensitivity for each asphalt-aggregate combinations depend on the type of antistripping agent used.

  29. Conclusions (Cont’d) • No single antistripping agent could work with all three aggregate types studied. Therefore, selection of proper antistripping agent will be unique for each project. • Among the three antistripping agents studied • Cecabase was found to be more effective with Riyadh asphalt mixtures. • Iterlene was found to be more effective with Ras Tanura asphalt mixtures

  30. Recommendations • More fundamental work is needed on the chemistry of asphalt-aggregate interaction for a better understanding of the chemical compositional factors that control asphalt properties..

  31. Thank you

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