1. Effect of Anti-Stripping Agents in Asphalt-Aggregate Interactionsby
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. Introduction and Background
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. Asphalt-Aggregate Bonding
* Wettability
* Viscosity (temp)
* Composition (oxygen)
* Durability
*Surface chemistry (mineral composition)
* Surface texture
* Porosity
* Surface condition (cleanliness, moisture)

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. Elemental Analysis (wt %) of RT and RY Asphalts
Elements
Sample ID
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
84.66
10.41
4.58
0.39
Nil
1.46
2.03
3.96 33
114
3.45
84.25
10.14
4.99
0.41
0.21
1.43
1.87
2.22
4.19 27 97
3.59

17. Physical Characteristics of RT and RY Asphalts

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

22. Properties of Aggregates

23. Recommended Dosage (wt %)
Anti-Stripping Agents
Flash Point
Chemical Name
Stability
Recommended Dosage (wt %)
Physical State
Product Name
S.No
>180oC
Alkylamido-imidazo
Polyamine
Heat Stable (170o C)
Liquid
ITERLENE IN/400-S 1
>100oC
Heat Stable
CECABASE 260 2
N-Alkyl ‘tallow’ dipropylene triamine
POLYRAM L200 3

24. Chromatography Column

25. 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

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

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

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

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

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

31. 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.

32. Among the three antistripping agents studied
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

33. 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..

34. Thank you