RSA Design Guidelines for hot-mix asphalt TRH3/HMA Workshop June 2001

Outline The Need for Change Project Organisation Project Outputs Overview of the guidelines

Why Change? - Traffic issues - Higher volumes at an early ageHigher volumes at an early age Increased axle loadsIncreased axle loads Increased tyreIncreased tyrepressures

TYRE INFLATION PRESSURE (kPa) % OF TYRE PRESSURE (1974) Average: 620 kPa (1995) Average: 733 kPa Tyre inflation pressure distributions in South Africa ( )

Why Change? - New design & construction - Increased use of SMA Ultra-Thin Asphalt Surfacings Thick Asphalt Bases

Why Change? - Design method deficiencies - Compaction issues Workability issues Fundamental evaluation of mastic Links between mix design, pavement design and performance

Why Change? - Influx of new methods - SHRP / Australian method Haphazard adoption of new principles may lead to fragmentation of knowledge

Project Organisation Steering CommitteeSteering Committee –Guidance, approval of direction and outputs Project Management GroupProject Management Group –Research coordination & management Technical Focus AreasTechnical Focus Areas –1. Components (G Jordaan/D Wright) –2. Spatial composition (M van de Ven) –3. Engineering properties (P Strauss) –4. Construction (G Rutland) –5. Design & performance (I van Wijk)

Project Management Group Steering Committee 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 Funders Approval of Direction & Outputs Advisory & Soundboard Execution & Accountability

Vision 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.

Scope all plant-mixed and paver-laid hot-mix asphalt, including thin surfacings and base course layersall plant-mixed and paver-laid hot-mix asphalt, including thin surfacings and base course layers all mix gradation typesall mix gradation types all bituminous binders currently used in South Africa and processes by which new binders can be incorporated in the design systemall bituminous binders currently used in South Africa and processes by which new binders can be incorporated in the design system application of HMA in both new roads and rehabilitation projects, taking cognisance of the prevailing environments of southern Africaapplication of HMA in both new roads and rehabilitation projects, taking cognisance of the prevailing environments of southern Africa

General approach Keep it simple, create common understandingKeep it simple, create common understanding Optimise use ofOptimise use of existing equipment Construction issuesConstruction issues Links to pavementLinks to pavementdesign

Project Outputs Synthesis of construction problemsSynthesis of construction problems Appropriate models for estimating stresses & strains in asphalt mixesAppropriate models for estimating stresses & strains in asphalt mixes Test methods for assessing effects of fillers on binder rheologyTest methods for assessing effects of fillers on binder rheology Test procedures for durability & stiffness quantification (binders)Test procedures for durability & stiffness 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 guidelines Intended as a practical guide to designers of HMAIntended as a practical guide to designers of HMA Contain guidelines on:Contain guidelines on: –Ranking of design objectives –Mix selection, taking traffic, climate, pavement structure, geometry and others into account –Selection and evaluation of components –Mix design processes (spatial design concepts and performance testing)