RPF 17 May 2001

1
Validation of Draft Guidelines for the Design of
HMA in SA

• OBJECTIVES
• Feedback
• Status of Validation

2
Scope of Presentation

• Design Procedures Performance Testing
• Study of Rut Resistance Testing
• Workshops on HMA Design Guidelines

3
Design Procedures Validated

• Selection of Mix Type
• Rating of Design Objectives
• Volumetric Design
• Bulk RD COMPACT Software
• Densely Graded Mixes
• Stone Mastic Asphalt

4
Volumetric Design of Densely Graded Mixes
5
Mod Marshall Compaction Voids Criteria
6
Volumetric Design of Stone Mastic Asphalt (SMA)

• Recommended Trial Binder Content
• BRD ? 2.75 BC 5.5 BRD lt 2.75 BC 6.0
• 4 Samples Compacted _at_ 50 blows
• VCA Coarse Aggr. ? Dry Rodded Test
• VMA ? 17.0 VIM ? 3.0
• VCAmix (with mastic) lt VCAdrc (without mastic)

7
Study of Rut Resistance Testing

• 8 Field Mixes
• Mixes paved on various roads, incl national and
  provincial roads and urban streets
• Actual designs based on Marshall Method
• 8 Laboratory Mixes (Experimental)
• Different Binder Contents
• Different Binder Mix Types

8
Field Mixes
9
Rut Resistance TestsValidated In Study

• Modified Marshall Compaction
• Gyratory Compaction
• Transportek Wheel Track Test (TWTT)
• Dynamic Creep Test
• Confined Impact Test (CIT)
• Axial Loading Slab Test (ALS)

10
Modified Marshall Compaction
11
Gyratory Compaction
12
Comparison of Gyratory and Modified Marshall
Compaction
13
Transportek WheelTracking Test (TWTT)
14
TWTT Downward Deformation
15
Gyratory Compaction vs TWTT
16
Confined Impact Test (CIT)
17
CIT Measurement of Deformation
18
CIT Performance Ratings
19
CIT Field Mixes
20
Dynamic Creep vs TWTT
21
Experimental Laboratory Mixes
22
Comparison of Rut Resistance ofLaboratory Mixes

• Modified Marshall Compaction
• Gyratory Compaction
• Transportek Wheel Track Test (TWTT)
• Dynamic Creep Test

23
Influence of Binder Content Modified Marshall
Compaction
24
Influence of Binder Content Gyratory Compaction
25
Influence of Binder Content Transportek Wheel
Track Test
26
Influence of Binder Type Modified Marshall
Compaction
27
Influence of Binder Type Transportek Wheel Track
Test
28
ConclusionsValidity of Rut Resistance Tests

• Modified Marshall Compaction
• Good Indicator of Workability Stability
• Gyratory Compaction
• Good Correlation of Terminal VIM with Rut
  Resistance
• Transportek Wheel Tracking Test
• Best Prediction of Rut Resistance

29
ConclusionsValidity of Rut Resistance Tests

• Dynamic Creep Test
• Not Applicable to Stone-Skeleton Modified
  Sand-Skeleton Mixes
• Confined Impact Test
• Validity Questionable

30
ConclusionsInfluence of Mix Composition

• Binder Content
• Higher Binder Contents ? Lower Rut Resistance
• Binder Type
• SBS Mod Mix ? Highest Rut Resistance
• SBR Mod Mix ? Lower than SBS Mod, but still Very
  Good
• EVA Mod Mix ? Similar to Non-modified Mix

31
Conclusions Workshops on HMA Design Guidelines

• Cape Province
• Venue University of Stellenbosch
• Date Tuesday, 12th June 2001
• KwaZulu Natal
• Venue Roads Dept. Pietermaritzburg
• Date Wednesday, 13th June 2001
• Gauteng
• Venue University of Pretoria
• Date Thursday, 14th June 2001
• Time 0800 ? 1700