PHILIP JOUBERT STEWART SCOTT

 Based on SAT Seminar (Pretoria)  Presentations by: Products: Cobus Venter – Geotrac Garth James – Kaytech Nicholas Reck – African Gabions Application: Mynhardt Augustyn– VKE Philip Joubert – Stewart Scott Analytical Techniques: Dr Fritz Jooste – Modelling & Analysis Systems Innovation Planning: Joop van Wamelen – Agrément SA BACKGROUND

 Products and Purpose  Applications  Theory (Modeling)  The Road Forward WHY GUIDELINES?

? Normally during rehabilitation action ? Grids/fabrics laid between old (distressed) and new asphalt overlay ? To Provide Increased Resistance to:  Reflective Cracking  Fatigue Cracking (strengthen pavement)  Deformation (Rutting)  Moisture/Fines Movement WHY REINFORCE ASPHALT?

Paving Fabrics:Geotextiles (Sealmac) Glass Fibre Grids:Glassgrid / Glasstex Polymer Grids:Polypropolene (AR - Grid) Steel Grids:Wiremesh (Road Mesh) Composites:Grid plus Fabric PRODUCTS

PAVING FABRIC

GLASS FIBRE GRID

STEEL GRID

COMPOSITE : GRID / FABRIC

PURPOSE

 Products and Purpose  Applications  Theory (Modeling)  The Road Forward WHY GUIDELINES?

RIGHT APPLICATION

TYPICAL APPLICATIONS

GLASS GRID FULL WIDTH

Percent Crack Reflection by length GLASS GRID FULL WIDTH

GLASS GRID STRIPS

USE OF INTERLAYERS

GRID AND FABRIC INTERLAYER

CONCRETE SLABS OVERLAY

GLASSGRID - SETTLEMENT CRACKS

PAVING FABRIC

POTENTIAL PROBLEMS

 Products and Purpose  Applications  Theory (Modeling)  The Road Forward WHY GUIDELINES?

WHY MODEL? To investigate effects of changing pavement parameters on pavement response Given Effect X, what is Strain-Y in Asphalt? How will asphalt perform at Strain-Y?

MICRO EFFECTS: UNCRACKED

Thickness and anisotropic effects distort calculated strains Strain unlikely to be reduced by Reinforcement UNLESS Reinforcement considerably stiffer than Asphalt, and there is zero slip

Micro Effects: Cracked-Behaviour

Expert Panel / National Interest Group, develop code of practice for Southern Africa, follow approach Euro committee/ TRB Group, formalise sound network management approach Product Performance Guarantee? Vast potential matrix of operating conditions, Difficult to follow this line of approach Agrément Certification? Standard conformance testing Rutting, Beam Tests, Fatigue Testing (MMLS) product approval / application type, within boundary conditions WAY AHEAD?

MICRO EFFECTS: CRACKED Some modelling is possible using FE Benefits of reinforcement are more obvious for cracked scenario BUT Anisotropic effects still important and likely to underestimate benefits of reinforcement Layered Elastic modelling not feasible

MODELLING POSSIBILITIES: SUMMARY Routine modelling is likely to underestimate benefits of reinforcement Routine modelling does not appear feasible at this stage Key Problem: Impact on damage inhibiting and crack retardation not evaluated at all

 Products and Purpose  Case Studies  Theory (Modeling)  The Road Forward WHY GUIDELINES?

WAY AHEAD Build Confidence: Focus on field performance and validation (80 %) Advanced modelling used mainly to identify key variables (5%) Improve routine models to be able to accommodate transfer functions (15%)

Y-Max BLI Case Studies PRODUCT X: OVERLAYS > 50 MM < > 600 < > 130 A,B,C D,E F,G,H

CASE STUDY INFORMATION Crack Type, Degree and Extent Maximum Deflection, Base Layer Index, Test Details Support Type and Thickness Traffic Volumes, Daily E80s Overlay and Construction Details

Base Layer Index MESA PRODUCT X: OVERLAYS > 50 MM Already Cracked Not Yet Cracked

Material Composition:  High tensile strength at low deformation  Shear adhesion to maintain good bond  Thermal and physically stable  No creep deformation  Recycle REQUIREMENTS FOR GOOD PERFORMANCE

Geometry:  Sufficient cross-sectional grid area to redirect tensile stresses (slip over existing pavement)  Mesh opening to achieve optimum shear adhesion  Opening such to promote aggregate interlock  Strip Width beyond crack REQUIREMENTS FOR GOOD PERFORMANCE

Constructability:  Easy placement  Remain secure during paving  Roll width REQUIREMENTS FOR GOOD PERFORMANCE

 Structurally sound (e.g. no excessive movement)  Evaluate condition (e.g. FWD, Crack Activity Meter)  First address structural problems (e.g. potholes, slab replacement)  Seal all large cracks  Pave leveling course  Overlay thickness (40mm; deeper more effective)  Tack coat (modify?)  Consider potential for slippage  Partial or full coverage (continuous = better) DESIGN GUIDELINES

 General description(e.g. glass fibre polymer covered  Tensile strength (e.g. 50, 100, 200kN/m)  Elongation at break(e.g. <5%)  Melting point(e.g. >200°C)  Mass per unit area(e.g. >300g/m 2 )  Storage(e.g. covered, dry, dust-free)  Pavement preparation(e.g. cracks, levelling, clean, damp)  Construction(e.g. tack, ripples, joints, roller, curves, paver/trucks) SPECIFICATION GUIDELINES

Boundary operating conditions Minimum Joint Efficiency (Crack activity), Maximum surface deflections, Maximum vertical alignment for rutting) National Reinforcement Register Identifying solution, Anticipated outcomes, Design criteria, Validation approach Crack mapping, Indices, TMH9 equivalent approach WAY AHEAD?