Bituminous Cold-Mix Technology and Pavement Design

1 7 Bituminous Cold-Mix Technology and Pavement DesignTRB WORKSHOP 153 SOUTH AFRICAN HIGHWAY Technology AND PRACTICEDr Fritz JoosteDirectorModelling and Analysis SystemsTopics of this Presentation: Some history, project background Motivation of development approach (focus on structural Design ) Materials classification task details Structural capacity assessment details ConclusionSome Recycling with emulsion and foam was done from the early 1970 s Initially fairly primitive & often applied to less highly trafficked roads by experienced designersSome deep cold-in place recycling with Emulsionin 1994 Some with Foamfrom 1996 onwardsExisting Cold-Mix Guidelines Emulsion materials Sabita Manual 14 (1993) Sabita Manual 21 (1999) Foamed bitumen materials TG2 Interim Guideline (2002)

2 Guidelines widely used, but need to Modernize & Improve Place foam and emulsion on equal footing Create a single, combined guideline Address need for paradigm shift in SABituminous Cold-Mix Guidelines Project initiated in 2005 to address deficiencies in existing guidelines Focus on mix designand structural designelements Limited time-frame: short term deliverable Somewhat novel structural Design approach adoptedFindings and methods will be incorporated into a larger, on-going Pavement Design development project (SANRAL sponsored)Project Constraints Reasonable knowledge base of performance (long-term and accelerated loading), but.

3 Not very detailed information, no fundamental material properties Current M-E Design method has deficiencies Adopted a Heuristicor Knowledge-basedpavement Design approach Simplified Design method, more emphasis on correct materials assessment, mix Design and constructionField Testing & AssessmentDesign Inputs & Rules of DesignMaterial Behaviour ModelsResponse Models & Capacity PredictionDesign FeasibilityAppropriate Spec sPractitioner/Human DomainResearch/Software DomainPavement Design ElementsPractitioner/Human DomainField Testing & AssessmentDesign Inputs & Rules of DesignDesign FeasibilityAppropriate Spec sPractitioner/Human DomainResearch/Software DomainMaterial Behaviour ModelsResponse Models & Capacity PredictionPavement Design

4 ElementsPractitioner/Human DomainTraditional ME Research Approach: Focus mainly on model and software development. Determining inputs, implementation and knowledge transfer is often neglectedField Testing & AssessmentDesign Inputs & Rules of DesignMaterial Behaviour ModelsResponse Models & Capacity PredictionDesign FeasibilityAppropriate Spec sPractitioner/Human DomainResearch/Software DomainPavement Design ElementsPractitioner/Human DomainVision for Medium Term Outcome: Develop a practical Design method that combines the best elements of current Design methods, and incorporates best practice elements of mechanistic analysis, field testing and constructionKnowledge Based Approach Gather all available field performance data Distil best elements of mechanistic analysis Validate and refine for robustness Develop clear, strong linkage to field testing and specificationsTo Date.

5 23 Field sites with construction, maintenance & performance info 7 HVS Sites (22 test sections) with construction & performanceThe Design ProcessLABDCPV isualsTest PitsFWDM aterials ClassificationCapacity AssessmentSpecificationsCBR 7-15%200 mm BSM 1130 mm C4> 200 mm G6 Mix Design Shear Strength Durability FlexibilityAdopt aspects of Certainty TheoryDCP Penetration (mm/blow) Materials Classification Using Certainty TheoryMaterial ClassClass 1 Class 2 Class 3 Class 4 Available InformationRule certainty = (Hypotesis|DCP Info) way of combining diverse types of evidence to reach a consistent, rational conclusion.

6 Also teaches young engineers the key factors affecting Design ProcessLABDCPV isualsTest PitsFWDM aterials ClassificationCapacity AssessmentSpecificationsCBR 7-15%200 mm BSM 1130 mm C4> 200 mm G6 Mix Design Shear Strength Durability FlexibilityDevelopment ApproachCBR 7-15%> 200 mm G6130 mm C4200 mm BSM 1 Design Parameter for Layer Range of Traffic Accommodated Rut situation, RQ situation Cracking situation Need for rehabilitationSystemPerformance IndicatorsReps to Failure ??Reps to Failure ??Reps to Failure ??Development ApproachCBR 7-15%> 200 mm G6130 mm C4200 mm BSM 1 Range of Traffic Accommodated Rut situation, RQ situation Cracking situation Need for rehabilitationArea = Shear Potential Fingerprint SystemPerformance IndicatorsSystem BehaviourIndicator ?

7 ??Octahedral Shear StrainCapacity Assessment ExampleCBR 7-15%1. Material Classes3. Subgrade LTES100 MPa2. Subgrade Class4. Adjust for region & subgrade cover97 MPa150 mm G6150 mm C4150 mm BSM2150 mm G75. Assign modular ratio s and Maximum EmodsMR = , EMax= 325MR = 3, EMax= 450MR = 4, EMax= 550 Capacity Assessment Example97 MPa175 MPa450 MPa550 MPa6. Determine Effective LTES for each layerOctahedral Shear Strain = Elastic TheoryVertical Compressive Strain on Subgrade = 237 microstrainHandling Reliability30 mesa10 mesa3 mesaPavement NumberAxles AccommodatedCategory A Roads (95% Reliability)Category B Roads (90% Reliability)CONCLUSION Project is ongoing, 90% of technical work to be completed in March, 2008 Efforts dedicated to Mix Design not covered, but this is a significant component (Project Leader.)

8 Prof Kim Jenkins) Aspects of the methodology to be incorporated in the broader revision of the SA Pavement Design methodThank you very muchfor your attention!TRB WORKSHOP 153 SOUTH AFRICAN HIGHWAY Technology AND PRACTICE