UNIVERSITY OF NAIROBI MASTERS OF SCIENCE IN CIVIL ENGINEERING (TRANSPORTATION) CE 462 SUPERPAVE HOT MIX ASPHALT DESIGN Presenter OTWANI J. A F56/67543/2013 NOVEMBER 2013

1.0 INTRODUCTION 1.1 Background : Superpave stands for SUperior PERforming asphalt PAVEments. (FHWA:US-DoT) Developed in the US (1987 – 1993) through the Strategic Highway Research Programme (SHRP) Adopted in SA in 2001 – blend of Marshall and Superpave.

1.0 INTRODUCTION 1.2 Problem statement Increasing traffic loads, traffic volumes and tyre contact stresses have resulted in increased incidences of premature distress (rutting, ravelling, cracking and potholes) Marshall method does not satisfactorily address secondary compaction.

1.0 INTRODUCTION 1.3 Research Questions What are the inherent deficiencies in the Marshall method of mix design? How does the superpave design method address the deficiencies in the Marshall method?

1.0 INTRODUCTION 1.3. Study objectives To outline inherent deficiencies in the Marshall method of HMA design. To illustrate how the superpave method addresses inherent deficiencies in the Marshall method of HMA design.

1.0 INTRODUCTION 1.4. Scope and Limitations of Study The study covers the superpave method of HMA design adopted from SA.

2.0 LITERATURE REVIEW 2.1 Overseas Road Note 19 Details the types of HMA Materials specifications for HMA Marshall design method Superpave design method Mix design specifications.

2.0 LITERATURE REVIEW 2.2 Strategic Highway Research Programme (FHWA, 1998) Initiated in 1987 by the US Congress 5-year, $150 million applied research program Aimed at improving the performance, durability, safety, and efficiency of the US highway system.

2.0 LITERATURE REVIEW 2.2 Strategic Highway Research Programme (FHWA, 1998)- cont…… Three primary objectives: Investigate why some pavements perform well, while others do not. Develop tests and specifications for materials  Work with highway agencies and industry to have the new specifications put to use.

2.0 LITERATURE REVIEW 2.2 Strategic Highway Research Programme (FHWA, 1998) – cont….. Results of SHRP: Superpave HMA design method. Three levels of design for low, intermediate and high traffic volumes (ESA). Complexity of mix design increases from level 1 to 3 Performance based criteria used to select mix design.

4.0 SUPERPAVE HMA DESIGN METHOD 4.1 FLOW CHART

4. 0 SUPERPAVE HMA DESIGN METHOD CONT’D 4 4.0 SUPERPAVE HMA DESIGN METHOD CONT’D 4.1 Selection of bitumen and source of aggregates Bitumen grade selected to suit temperature conditions and traffic loading.(Pen, Softening point) Aggregates tested to confirm compliance with specs (LAAV, SSS, FI, ACV)

4.0 SUPERPAVE HMA DESIGN METHOD CONT’D 4.1 Grading of aggregates

4.0 SUPERPAVE HMA DESIGN METHOD CONT’D 4.1 Grading of aggregates cont

4.0 SUPERPAVE HMA DESIGN METHOD CONT’D 4.1 Grading of aggregates cont Aggregate single size and combined grading   Agg size 14-30mm 6-14mm 3-6mm 0-3mm Filler GRADING Proportions Theoretical Actual Control points Sieve 39 20 12 29 grading sieve min max 37.5 100 28 99 25 90 64 86 88 19 14 72 73 2.36 45 6.3 0.5 4 42 43 0.075 1 7 2 75 22 21 Caution zone 47 13 0.3 4.75 39.5 11 3.2 3 26.8 30.8 1.18 18.1 24.1 0.6 13.6 17.6 Flakiness Index 18.6 17.5 11.4

4.0 SUPERPAVE HMA DESIGN METHOD CONT’D 4.1 Grading of aggregates cont

4. 0 SUPERPAVE HMA DESIGN METHOD CONT’D 4 4.0 SUPERPAVE HMA DESIGN METHOD CONT’D 4.1 Compaction of superpave mix design

Constant pressure of 600 kPa on compacting ram. 4.0 SUPERPAVE HMA DESIGN METHOD CONT’D 4.1 Compaction of superpave mix design cont’d Constant pressure of 600 kPa on compacting ram. Constant rate of rotation of the mould at 30 gyrations per minute Mould positioned at compaction angle of 1.25 degrees. Compaction effort depends on design traffic loading

4. 0 SUPERPAVE HMA DESIGN METHOD CONT’D 4 4.0 SUPERPAVE HMA DESIGN METHOD CONT’D 4.1 Compaction of superpave mix design cont’d

4. 0 SUPERPAVE HMA DESIGN METHOD CONT’D 4 4.0 SUPERPAVE HMA DESIGN METHOD CONT’D 4.1 Compaction of superpave mix design cont’d

4. 0 SUPERPAVE HMA DESIGN METHOD CONT’D 4 4.0 SUPERPAVE HMA DESIGN METHOD CONT’D 4.2 Refusal density determination

4. 0 SUPERPAVE HMA DESIGN METHOD CONT’D 4. 2 4.0 SUPERPAVE HMA DESIGN METHOD CONT’D 4.2.1 Mix properties at refusal density Refusal density Test by Vibrating Hammer Method   Binder content 3.5 4.0 4.5 Refusal density 2.225 2.249 2.26 Maximum specific gravity 2.380 2.364 2.348 Refusal voids in mix 6.5 4.9 3.7 Voids in mineral aggregates 13.4 12.9 13.0 Voids filled with Binder 51.5 62.5 71.2

4. 0 SUPERPAVE HMA DESIGN METHOD CONT’D 4. 2 4.0 SUPERPAVE HMA DESIGN METHOD CONT’D 4.2.2 Refusal density property curves

4. 0 SUPERPAVE HMA DESIGN METHOD CONT’D 4. 2 4.0 SUPERPAVE HMA DESIGN METHOD CONT’D 4.2.3 Determination of optimum bitumen content Parameter   BC 1. At 4.0% Refusal voids 4.4 2. A 13.0 %Voids in Mineral Aggregates 3.9 3. At 65% Voids Filled With Binder 4.1 Total 12.4 Average Design binder content from vibrating hammer test 4.1%

4. 0 SUPERPAVE HMA DESIGN METHOD CONT’D 4. 2 4.0 SUPERPAVE HMA DESIGN METHOD CONT’D 4.2.4 Mix properties at design binder content Summary of DBM mix properties at the design binder content (4.1%)   Parameter Unit Result Specifications Min Max Marshall stability @ 60°C   KN 12.8 5 Flow (mm) 3.4 2 Voids in Mix from marshall test (%) 6.9 4 10 Voids in Mix from V.H test 4.7 3 Voids in mineral aggregates 12.9 12 Voids filled with bitumen 65 75

4.3 MARSHALL HMA DESIGN METHOD 4.3.1 Marshall test data Binder Content (%)   3 3.5 4.0 4.5 5.0 Theoretical Max. Relative Density 2.397 2.381 2.365 2.348 2.333 Bulk Relative Density 2.172 2.191 2.193 2.209 2.203 Voids in mix(%) 9.4 8.0 7.3 5.9 5.6 Voids in mineral aggregates(%) 15.0 14.7 15.1 14.9 15.6 Voids filled with Binder(%) 37.5 45.9 52.0 60.2 64.4 Stability (KN) 12.65 13.09 12.51 12.15 10.59 Flow(mm) 2.7 3.3 3.9

4.3 MARSHALL HMA DESIGN METHOD 4.3.2 Marshall design curves

4.3 MARSHALL HMA DESIGN METHOD 4.3.2 Marshall design curves cont…

4. 3 MARSHALL HMA DESIGN METHOD 4. 3 4.3 MARSHALL HMA DESIGN METHOD 4.3.3 Determination of optimum bitumen content. From the Marshall design curves:    Parameter BC At maximum Density 4.6 2. At maximum Stability 3.5 3. At 7% VIM 4.0 4. At 3.5 mm Flow 4.3 5. At 14.9% VMA 6. At 65% VFB 5 TOTAL 24.9 Average = 4.2 Therefore, the Optimum Binder Content from the Marshall test is, 4.2% 

4. 3 MARSHALL HMA DESIGN METHOD 4. 3 4.3 MARSHALL HMA DESIGN METHOD 4.3.4 Calculation of Voids In Mineral Aggregates (VMA).

4. 3 MARSHALL HMA DESIGN METHOD 4. 3 4.3 MARSHALL HMA DESIGN METHOD 4.3.5 Calculation of Voids In Mix (VIM).

4. 3 MARSHALL HMA DESIGN METHOD 4. 3 4.3 MARSHALL HMA DESIGN METHOD 4.3.6 Calculation of Voids Filled with Bitumen (VFB).

QUESTIONS, COMMENTS AND SUGGESTIONS THANK YOU QUESTIONS, COMMENTS AND SUGGESTIONS