RSA Design Guidelines RSA Design Guidelines for hot-mix asphaltfor hot-mix asphalt

TRH3/HMA TRH3/HMA WorkshopWorkshop12-14 June 200112-14 June 2001

OutlineOutline

• The Need for Change

• Project Organisation

• Project Outputs

• Overview of the guidelines

Why Change?Why Change?- Traffic issues -- Traffic issues -

• Higher volumes at an early ageHigher volumes at an early age

• Increased axle loadsIncreased axle loads

• Increased tyre Increased tyre

pressurespressures

1200 1400200 400 600 800 10000

5

10

15

20

25

TYRE INFLATION PRESSURE (kPa)

% O

F T

YR

E P

RE

SS

UR

E

(1974)

Average: 620 kPa

(1995)Average: 733 kPa

Tyre inflation pressure distributions in South Africa (1974 - 1995)

Why Change?Why Change?- New design & construction -- New design & construction -

• Increased use of SMA

• Ultra-Thin Asphalt Surfacings

• Thick Asphalt Bases

Why Change?Why Change?- Design method deficiencies -- Design method deficiencies -

• Compaction issues

• Workability issues

• Fundamental evaluation of mastic

• Links between mix design, pavement design and performance

Why Change?Why Change?- Influx of new methods -- Influx of new methods -

• SHRP / Australian method• Haphazard adoption of new principles may

lead to fragmentation of knowledge

Project OrganisationProject Organisation• Steering CommitteeSteering Committee

– GuidanceGuidance, approval of direction and outputs, approval of direction and outputs

• Project Management GroupProject Management Group– Research coordination & managementResearch coordination & management

• Technical Focus AreasTechnical Focus Areas– 1. 1. Components (G Jordaan/D Wright)Components (G Jordaan/D Wright)– 2. Spatial composition2. Spatial composition (M van de Ven) (M van de Ven)– 3. Engineering properties3. Engineering properties (P Strauss) (P Strauss)– 4. Construction4. Construction (G Rutland) (G Rutland)– 5. Design & performance5. Design & performance (I van Wijk) (I van Wijk)

Project Managemen

t Group

Steering Committe

e

RPF & SAT

Interest Groups

TFA1 Leader

TFA2 Leader

TFA3 Leader

TFA4 Leader

TFA5 Leader

Project Tasks

Integrated

Activities

Implementation of System in

Industry

Advisory Groups

Advisory Groups

Advisory Groups

Advisory Groups

Advisory Groups

Funders

Approval of Direction & Outputs

Advisory & Soundboard

Execution & Accountability

VisionVision

• To develop a new southern African hot-mix asphalt design method for use by practitioners, educational institutions and research organisations, which will be integrated with pavement design, construction and expected performance, which will yield improved and appropriate designs for all situations and concomitant savings, based on the best available technologies (developed locally or imported) and on sound practice, and which will be implemented in the next five years.

ScopeScope

• all plant-mixed and paver-laid hot-mix asphalt, all plant-mixed and paver-laid hot-mix asphalt, including thin surfacings and base course including thin surfacings and base course layerslayers

• all mix gradation typesall mix gradation types• all bituminous binders currently used in South all bituminous binders currently used in South

Africa and processes by which new binders Africa and processes by which new binders can be incorporated in the design systemcan be incorporated in the design system

• application of HMA in both new roads and application of HMA in both new roads and rehabilitation projects, taking cognisance of rehabilitation projects, taking cognisance of the prevailing environments of southern Africathe prevailing environments of southern Africa

General approachGeneral approach

• Keep it simpleKeep it simple, create common understanding, create common understanding• Optimise use of Optimise use of

existing equipmentexisting equipment• Construction issuesConstruction issues• Links to pavementLinks to pavement

designdesign

Project OutputsProject Outputs• Synthesis of construction problemsSynthesis of construction problems• Appropriate models for estimating stresses & Appropriate models for estimating stresses &

strains in asphalt mixesstrains in asphalt mixes• Test methods for assessing effects of fillers on Test methods for assessing effects of fillers on

binder rheologybinder rheology• Test procedures for durability & stiffness Test procedures for durability & stiffness

quantification (binders)quantification (binders)• Methods for evaluating rutting & fatigueMethods for evaluating rutting & fatigue• Mapping of pavement temperatureMapping of pavement temperature• Condition & compaction of asphalt (lab)Condition & compaction of asphalt (lab)• Conceptualisation of Spatial CompositionConceptualisation of Spatial Composition• Lab study on fatigue of asphaltLab study on fatigue of asphalt• Assessment of asphalt ruttingAssessment of asphalt rutting• Validation of proposed guidelines for ruttingValidation of proposed guidelines for rutting

Overview of the guidelinesOverview of the guidelines

• Intended as a practical guide to designers Intended as a practical guide to designers of HMAof HMA

• Contain guidelines on:Contain guidelines on:– Ranking of design objectivesRanking of design objectives– Mix selection, taking traffic, climate, pavement Mix selection, taking traffic, climate, pavement

structure, geometry and others into accountstructure, geometry and others into account– Selection and evaluation of componentsSelection and evaluation of components– Mix design processes (spatial design concepts Mix design processes (spatial design concepts

and performance testing)and performance testing)