Product Properties, Classification, Selection and Application

1. Product Properties, Classification, Selection and Application T Distin Colas South Africa

2. Product Properties Section 3

3. Product Properties Major properties influencing performance: • Cohesion • Adhesion • Rheology • Elasticity • Stiffness • Ageing • Compatibility/storage stability

4. Product Properties cont… • Modified products should be assessed as a whole • full asphalt mix design to ascertain desired properties achieved • Thermo-mechanical history will have major effect on behaviour in terms of: • blending technique • blending temperature • high shear pumping • storage temperature

5. Cohesion • A measure of the tensile stress to break the molecular bond • A binder with high cohesion requires high tensile stress to cause failures • Binders with low cohesion break easily • Cohesive properties if measured by empirical tests (eg penetration or R&B) are significantly changed by modification with thermoplastic polymers

6. Cohesion cont… • Increase in polymer gives large increases in softening point but small increases in penetration • Standard ductility not appropriate for modified binders • Force-ductility gives a better indication of cohesive strength • Cohesive properties influence how: • soon a surface seal is opened to traffic • its ability to withstand traffic shear stresses

7. Elastic phase Force Toughness Elongation Typical Force-ductility relationship

8. Adhesion • Measure of the stress required to break the binder aggregate bond • “Wetting” of aggregate is controlled by the binder’s viscosity properties • Adhesion influenced by presence of water (during construction and in-service) • It is more difficult to achieve good adhesion with hydrophilic aggregates • Hot modified binders • develop increased cohesive strength at the expense of increased adhesion • are less able to “wet” and adhere to the aggregate

9. Influence on cohesion/adhesion properties Cohesion Force Adhesion Mode of failure % Modifier

10. Adhesion cont… • Failure mode in seals using highly modified binders more likely to be adhesion (especially during cold weather) • Higher binder thickness improves bond • Aggregate needs to be clean and dry • Time between binder and aggregate application kept to a minimum • Pre-coated aggregates helps adhesion • Use of cutters to help early adhesion not recommended • Addition of commercial adhesion agents may be considered in high risk areas

11. Adhesion testing • No test available showing clear performance-based relationship • Modified Vialit test (MB-7) recommended to predict adhesion of binder to the aggregate • Pull-out test (MB-8) and Pliers test (MB-9) are useful early indicators of adhesion

12. Rheology (flow behaviour) • At high temperatures and/or long loading times, binders behave as viscous liquids resulting in large permanent deformation • At low temperatures and/or short loading times, binders behave as elastic (brittle) solids, with recovery of deformation • Rheology of conventional binders is easy to predict with simple tests (Penetration, R&B and Viscosity) • Rheology of modified binders highly complex

13. Influence of Softening Point and Viscosity on modifier content SBR Viscosity SBS EVA Softening point SBS EVA SBR Polymer content (%)

14. Rheologycont… • Softening Point of modified binders decreases during storage over time • Long haul distances or delays may require a small increase in modifier • Addition of polymer results in lower moduli at low temperatures giving rise to more flexibility • At high temperatures binder shows improved stiffness

15. Rheology tests Dynamic Shear Rheometer • Behaviour of binder over a range of loading and temperature conditions • Typical design parameters are Dynamic Stiffness (G*) and Phase Angle (δ) • Phase angle measures relative elastic and plastic properties • Not included as a mandatory test • Recommended for special or high risk applications

16. Elasticity • Indicates binder recovery to its initial shape when a load is removed • Used to measure • fatigue resistance in a binder • its ability to absorb large stresses without cracking • Elastic property influenced by type and degree of modification • SBS has high elastic recovery • SBR relatively lower elastic recovery • EVA no elastic recovery but high stiffness • Torsional Recovery (method MB-5) has been introduced as a quality control tool

17. Torsional Recovery relationship TORSIONAL RECOVERY % POLYMER CONTENT

18. Stiffness • Property indicates the strain under particular stress conditions • Stiffness modulus is a function of load: • size • time • temperature • Direct correlation between stiffness of the binder and permanent deformation under repetitive loading in asphalt layer • Binders with higher stiffness should be used in asphalt layers exposed to high stress conditions

19. Ageing • Measurement of gradual changes in engineering properties over time caused by: • heat • oxidation • UV radiation • loss of volatiles • Modified binders are generally more resistant to ageing • Binders and polymers degrade if not stored correctly

20. Ageing • Most significant ageing of binders occurs during asphalt mixing in the drum • Binders continue to age in service • Ageing characteristics determined by the modified RTFOT (MB-3) • Pressure Ageing Vessel test models ageing but no requirement in current guideline

21. Compatibility/Storage Stability • Definition of compatibility • Where the bitumen and polymer consist of a single phase with no separation during storage without agitation • Where the bitumen and polymer can be combined into a two-phased product behaving essentially as a single-phased product • Solubility of the polymer in bitumen dependant on two main parameters: • Difference in solubility of the polymer and the maltene phase of the bitumen • Amount and type of asphaltenes in the bitumen

22. Compatibility/Storage Stability cont… • Storage stability test recommended for assessment of stability/suitability of modified products • Test should not be seen as a performance indicator • Manufacturer should supply method statement on circulation and storage techniques

23. Modified Binder Classification Section 4

24. Modified Binders Non-homogenous Homogenous Bitumen-rubber Plastomer Elastomer Crumb rubber EVA SBR SBS Generic classification of modified binders

25. Classification System Classified according to: • Applications in which they perform surfacing seals asphalts crack sealants • Modifier group use in the binder elastomer type polymer plastomer type polymer crumbed rubber • Product properties Numerical – higher number indicates improvedproduct performance properties

26. Letter coding S - surfacing seal (hot applied) SC - surfacing seal (cold applied) A - hotmix asphalt C - crack seal (hot applied) CC - crack seal (cold applied) E - elastomer type polymer (SBR, SBS) P - plastomer type polymer (EVA) R - crumbed rubber

27. Modified Binder Class (S) Application S - E1 Surface Seal - Hot applied S - E2 Surface Seal - Hot applied S - R1 Surface Seal – Bitumenrubber SC - E1 Surface Seal - cold applied (emulsion) SC - E2 Surface Seal - cold applied (emulsion) Classification for Surface Seals

28. Modified Binder Class (A) Application A - E1 Hotmix asphalt - Fatigue A - E2 Hotmix asphalt - Fatigue / Deformation A - P1 Hotmix asphalt - Deformation A - R1 Hotmix asphalt - Bitumen rubber Classification for HMA

29. Modified Binder Class (C) Application C - E1 Crack Sealant - Hot applied CC - E1 Crack sealant - Cold applied C - R1 Crack Sealant - Hot applied Classification for Crack Sealing

30. Selection and Application Criteria Section 5

31. Environmental Influences - Seals • Climatic conditions more restrictive for application of hot modified binders • Aggregate loss due to rain soon after application is a real risk due to poor aggregate “wetting” • Addition of cutter may solve the problem in the short term but this may cause future bleeding problems • expert advice needed • Cutters should not be considered for high stress applications

32. Binder Class Minimum Road Surface Temp. (°C) S - E1; S - E2 25 SC - E1; SC - E 2 10 S - R1 25 Minimum Road Surface Temperatures for Surface Sealing

33. Environmental Influences - HMA • Rapid increase in viscosity due to cooling could cause compaction problems • Mainly in cold weather and when constructing thin layers • Rolling must commence and be completed as soon as possible after application

34. High Stress Surface Seals • Durability of seals determined by: • residual binder properties • associated film thickness • Highly stressed area is one of following: • >30 000 elv per lane per day (TRH 3:1998 classification) • Curve radii < 50m • Steep gradients >5% • Moderately stressed area is one of following: • 10 000 to 30 000 elv per lane per day • Curve radii < 100m • Gradients < 5%

35. Modified Binder Class Condition S-E1 S-E2 SC-E1 SC-E2 S-R1 Active cracks    Passive cracks     Moderately stressed areas   Highly stressed areas    Surface temp at application (>10 deg C)   Very high road surface temperatures    Selection Criteria for Surface Seals

36. Stress Absorbing Membranes • SAMIs applied to absorb strains that could result in reflection cracks • Selection criteria same as previous Table for active cracks • Local experience with bitumen-rubber seals • More information in TRH 3

37. Binder Class Condition A-E1 A-E2 A-P1 A-R1 High deformation resistance on stiff base   High deformation resistance on flexible base   High fatigue resistance on flexible base   Moderate fatigue resistance and moderate deformation resistance  Reflective cracking   High stress areas    Open graded mixes with high film thickness   Low road surface temperatures   Hotmix Asphalt

38. Crack Sealing • Active cracks indicate deep structural deficiencies • Generate high vertical and horizontal movements • Performance of crack sealant dependant on its stiffness at the minimum pavement temperatures • Widening narrow cracks reduces stresses on sealant • Sabita Manual 20 gives more details of best practice for crack sealing

39. Crack Sealing properties Specific binder properties for range of environmental conditions: • Adequate adhesion • Low flow values at high temperatures (60ºC) • Low moduli at low temperatures (-10ºC) • Sufficient elasticity to accommodate crack movements without cracking