SATC HVS WORKSHOP

Background to HVS Technology

Louw du Plessis13 July 2007

Contents

• What is APT• Different types of ATP devices• Brief history on the development of the South African

HVS programme• Current and Future Developments• Current HVS test programme

• International• Local

• HVS Testing Objectives• Benefits of testing• Limitations• HVS Planning

What is APT• Pavement Design methods based on Computer

modeling, Laboratory data, field investigations• To measure our success we have to built a full-scale

pavement, subject it is years of traffic and evaluate the performance (LTTP)

FWD

Test Pits

Visuals

DCP

LAB

What is APT • APT bridging the gap between Lab designs and LTPP

BE

NE

FIT

LOW

ME

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C o m p u te r S im u la t io n /E n g in e e r in g J u d g e m e n t

F ie ld T e s tin g

L a b o ra to ry T e s tin g

L o n g T e rm P a v e m e n tP e r fo rm a n c e S tu d ie s

A c c e le ra te d P a v e m e n tT e s tin g

C O S TL O W M E D IU M H IG H

Hugo et al, 1991

What is APT • Simulates traffic in an accelerated manner in

controlled conditions

• “Quick” assessment of damage caused by heavy traffic

• Do not have to waityears to evaluateyour design

What is APT • Helps us to understand how various pavement

materials and layers in a composite pavement structure behave under the influence of the environment and traffic

• It’s a tool to assist us in the designing of pavement structures to withstand the applied loads without pre-mature failures or being too expensive

Different types of APT Devices• USA

• Turner Fairbank Highway Research Centre• FAA National Airport Pavement Test Facility• Westrack• MnRoad• Louisiana Test Track Centre (LTRC)• Accelerated Pavement Load Facility (Ohio State

University)• Europe

• LCPC (Nantes, France)• CEDEX (Spain)• LINTRACK (TU Delft, Netherlands)• Danish Road Testing Machine (RTF) UT Denmark• Transportation Research Laboratory, UK• Pavement Test Facility, Nottingham, UK

• Australia & New Zealand• ALF• CAPTIF (Canterbury APT Indoor Facility)

Examples• VT Smart Road

The Virginia Smart Road, full-scale test road.

• WESTRACK

• Mn Road

CIRCULAR TEST TRACKS

• CAPTIF, New Zealand

• Manège de Fatigueat LCPC, FRANCE

More Examples

• Lasi, Romania

• CEDEX, Spain

More Examples

• PTF, TRL, UK

• LINTRACKUT Delft

• RTM, Denmark

South African version of an APT device –The Heavy Vehicle simulator (HVS)

History of the HVS programme• During 1960’s SA developed an analytical pavement

design procedure, but field verification of the models was required

• To determine the effect of abnormal vehicles on roads full-scale test sections loops were constructed on the premises of the CSIR. Normal heavy vehicles were used to apply the traffic

• Due to the slow rate of load applications a accelerated testing facility was designed to replace the heavy vehicles

• HVS Mk I: Bailey bridge, wheel pushed back & forth by an agricultural tractor

History Continue• Major limitation of Mk I: system was not mobile – test

sections had to be constructed under the Bailey bridge structure.

• Lead to the development of the first fully self-powered mobile accelerated testing device, the HVS Mk II

• Max load 75kN, linear tracking, single full-scale wheel

HVS MK II• Main purpose:

• Determination of load equivalency factors• Rutting in un-treated granular layers• Load associated cracking in cement treated bases

• By 1975 24 tests were successfully conducted with HVS MkII• Data collected: Deflections, Radius of curvature, permanent

deformation, visual distress (cracks, shear failures)

HVS MK III• Main motivation: Severe failures of a new coal delivery road. 18 tests

with the Mk II were conducted to identify the cause of the problem • Results so promising that By 1972, CSIR motivated for the

manufacturing of 3 improved HVS models.

HVS MK III• Standard truck dual-wheel & aircraft wheel configuration• Uni- & bi-directional loading• Max load 200 kN• Ave production: 18 000 repetitions per day• On-board power• Mechanical hydraulic control• Testing area: 1 x 8m

HVS MK III testing objectives• Refinement of load equivalency factors• Verification of new designs as proposed by the new design method• Extend data to the 4 climatic regions in SA• Verify theoretical predictions of distress in cemented base layers• Refine the prediction models of fatigue cracking in Bituminous

pavements• Evaluate stress-dependant response for overlay design purposes

HVS MK IV +

• Delivered in 1999• Computer controlled, hydraulic servo-valve close-loop feedback system• Wireless LAN for distant monitoring & control• 30 – 205 kN moving constant load• 30 – 110 kN moving dynamic loads

• 0,5 – 3,0 c/section, 20 % load variation• 24 000 reps/day, max wheel speed 12.8 km/h

Further Developments: HVS Mk VI

• Significantly cheaper than Mk IV+ • System upgradeable to exceed Mk IV capabilities• Test section length increased to 12m • Improved wheel speed (12.8 – 20 km/h)• Eliminate vehicle frame• Reduce complexity• Use turntable trailer axles to move laterally• On site mobility – use terminal tractor• Long haul mobility – as for Mk IV• Single and dual wheels• Externally powered – line power or generator

In Transit

Associated Pavement Monitoring Instrumentation

RSD data output

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-0.050

0 1 2 3 4 5 6 7Distance

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lect

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(mm

)

International HVS programmes

UC Davis / Berkeley HVS programme• Started in 1994 with a pilot study in SA• Bought 2 fully refurbished HVS Mk III’s from SA:

• One unit used in field Studies (Feb 1995)• 2nd Unit used at the University (May 1995)

UC Davis / Berkeley HVS programme:Core activities

• Comparative testing: Full depth AC overlay vs half depth Bitumen-rubber overlay

• Evaluation of Asphalt Treated Permeable Base• AC Rutting & Fatigue study• Foamed bitumen base stabilization• Rapid Rehabilitation - Long Life PCC

• Evaluation of Fast Set Cement PCC sections• Dowel bar retrofit evaluation• Evaluation of Pre-cast Concrete panels

Latest Field Project:Pre Cast PCC panel evaluation

Placed with Cranes on specially prepared cemented base

ERDC – CRREL:Cold Regions Research and Engineering

Laboratory Hanover, NH

Delivery of the first Mk IV in Feb 1997

Test Facility at CRREL

Current HVS focus areas• Pavement Subgrade Performance for New

Mechanistic Design19 states + FHWA

• Geogrid Base Course Reinforcement to Extend Pavement Life9 states + FHWA

Deliverable ProductsExperimental Research+

Analytical Research

Subgrade failure criteriaPavement Subgrade ModelsDatabase

Sweden / Finland HVS Program(VTT & VTI) (May 1997)

Focus areas

• Mechanistic Design of Semi-Rigid Pavements• Stability tests of modified AC-layer• Evaluation of the Swedish Pavement Design Specification• Evaluation of different strengthening strategies on existing

roads in some European countries

US Army Corps of Engineers

Waterways Experimental Station

World’s biggest HVS HVS V (Dec 1998)• 36.3 m long, 102 tonnes• Test section length 12m, max load = 440kN• Single & Dual Aircraft wheels

Current Activities• Rapid Airfield Construction

• Repair Materials, Mats, Stabilization• Airfield Damage Repair• Rapid Parking Expansion

Repair Requirements

• Ready for C-17 in less than 1 day (“rapid repairs”) or 3 hours (“very rapid repairs”)• Consistent with ASTM C 928• Testing of Polymeric, Asphaltic & Cemetitious

products• Simple procedures and little equipment• Should last a couple of years and sustain several

thousand aircraft operations

Instant Matting System EvaluationsInstant Matting System Evaluations

USA, Florida, HVS programme

(June 2000)

APT FACILITYDedicated test tracks• Asphalt paved track• Concrete paved track• Dedicated test pits• Water table controlled

Full Lab capabilities• Asphalt• Concrete• Aggregates / Soils

FDOT HVS Testing programme• Effects of Polymer modification on SuperPave mixes• Rutting performance of Coarse and fine-grained mixtures• Early strength requirements for PCC slab replacements• Composite Pavement studies

Early Strength requirements PCC slabsDetermine minimum opening strength required to open lane to traffic at 6 hr.

South African HVS ProgrammeGauteng Department of Public Transport, Roads and Works

HVS Activities 2003- 2006• Concrete pavements • Cold in situ recycling

with ET & FT • Pavement - vehicle

interaction

Concrete study I: Objectives

• Investigate the influence of the environment and load on joint deterioration (improve cncPave)• Plain aggregate interlock joints• Doweled joints• On 2 aggregate types

Concrete Study II:The Evaluation of a Ultra Thin Continiously Reinforced Concrete

Pavement

Ultra Thin Continuously Reinforced Concrete Pavement (UTCRCP)

• 20 to 40 mm Layer Thickness • 50 x 50 mm (Ø5mm to Ø8mm) Welded Mesh

• Normal deformed bar (+ - 450 MPa tensile strength)• 4.5% versus 0.6% Steel for Traditional CRCP

• Ultra High Strength Cement (UHSC) .

200mm

50mm

10mm35 mm thickconcrete

Normal 3.7 m lane width

10mm steel distance keepers

8mm steel meshplaced at 50mm intervals

30 mm thickAC layer

Typical failures of UTCRCP

Crack Movement

Cold in situ recycling

Investigations on Emulsion & Foam Treatments• Compaction potential of foam and emulsion treated materials• APT evaluation of emulsion and foam treated recycled base• Accelerated curing methods for foam and emulsion treated

materials• Establishment and monitoring of LTPP sections

Objectives

• Determination of failure mechanism (s)• Determine the load equivalence for the test section.• Determine the reasons for the good performance of the section.

Pavement-vehicle interaction

Stress in motion (SIM) measurements• Improved understanding of vehicle contact stresses and

strains – improvements to the SAMD• Application in HVS testing and pavement design

Pavement-vehicle interactionImportant Conclusion• Vertical contact stress vs tyre inflation pressure:

AMVCS is 1.2 to 2.58 times greater than tyre inflation pressure

Gautrans HVS reportswww. gautrans-hvs.co.za

TITLE REPORT NO. AUTHOR APPROVED SUBMITTE

Concrete pavement research. Construction report: CR-2004/33. HVS

testing of the concrete test sections on the N3 near Hilton.

Version: Final

CR-2004/33 AC Brink May 2005 July 2005

Second level analysis of Hilton concrete sections NA P Strauss May 2005 July 2005

Establishment of two LTPP experiments in association with HVS tests

on Road D2388 in GautengCR-2005/03 D Jones May 2005 May 2005

Establishment of an LTPP experiment in association with HVS tests on

Road P243/1 in GautengCR-2005/04 D Jones May 2005 May 2005

Initial monitoring of the LTPP experiment in association with HVS tests

on Road P243/1 in GautengCR-2005/06 D Jones May 2005 May 2005

Initial monitoring of the LTPP experiments in association with HVS

tests on Road D2388 in GautengCR-2005/05 D Jones May 2005 May 2005

First Level Analysis report: HVS Testing of the concrete test sections

on the N3 near Hilton: Tests 421A5 to 423A5CR-2004/43

AC Brink

L du PlessisMay 2005 July 2005

First Level Analysis report: HVS Testing of the concrete inlay test

sections on the N3 near Hilton: Test 424A5.CR-2004/59 L du Plessis May 2005 July 2005

Chinees HVS Programme

• China recently became the first Asian country to order an HVS

• Prof Sha of Chang’an University in Xian (ShaanxiProvince)

• Ordered a HVS Mk VI• Expected delivery Jan 2008

Objectives and Benefits of HVS testing

• Long-term

• Improvement of current Pavement Design practices• Development of Structural design methods for new

technologies• General development of skills in the fundamental

understanding of material behaviour• Puts us in the fore-front of pavement design technology

• Short-term

• Optimization of a material design• Performance evaluation of a particular pavement structure• Comparative testing evaluating various alternatives• Proof testing of new technologies (Cost avoidance)• Fit-for-purpose designs

Objectives and Benefits of HVS testing

Reduction of pavement costs by reducing unnecessary pavement thickness, or by improving the structural balance of the designAvoidance of failure caused by the use of unproven designs or by abnormally heavy trafficImproving pavement design methods including both new and rehabilitation methodsGreater knowledge and understanding of pavement and materials behaviourRapid evaluation and comparison of rehabilitation measures for flexible, semi-flexible (stabilised) and rigid pavements

Objectives and Benefits of HVS TestingGauteng, national & SADC pavement design standards and guidelinesMaterial specifications and guidelinesDevelopment of human resourcesCapacity building in industryInnovative products and designs

Objectives and Benefits of HVS testing

SA pavement design and analysis:

• Structural design manual (TRH4)• Rehabilitation design manual (TRH12)• SA mechanistic design and analysis method• Calibration of the DCP rehabilitation method• Calibration of cncPave for Concrete pavement designs

SA materials characterization

• Asphalt mix design manual (TRH8)• Materials classification and selection (TRH14)• Sabita manuals, Foam and emulsion mixes, large

aggregate mixes for bases (LAMBS)

Breadth of benefits

Materials/methodsdevelopment of a new large-stone mix design method; use of modified binders in mixes; in situ recycling of materials (using cement, lime, foamed bitumen and bitumen emulsion); block paving (masonry and concrete); coarse power station generator ash; roller compacted concrete; slag; bitumen-rubber; waterboundmacadam; recycled asphalt base; upgrading of gravel roads; marginal natural aggregates with various additives; high quality granular bases; evaluation of drainage layers as structural layers; lime-stabilized sand subbases under bitumen; design and rehabilitation procedures for concrete roads; lightly-cemented base pavements; identification and evaluation of cost-effective rehabilitation techniques; evaluation of labour-intensive construction methods; testing various asphalt base pavements and improving the design, analysis and understanding of the behaviour of such pavement types; porous asphalt

Breadth of benefits

Materials/methods development of a new large-stone mix design method; use of modified binders in mixes; in situ recycling of materials (using cement, lime, foamed bitumen and bitumen emulsion); block paving (masonry and concrete); coarse power station generator ash; roller compacted concrete; slag; bitumen-rubber; waterbound macadam; recycled asphalt base; upgrading of gravel roads; marginal natural aggregates with various additives; high quality granular bases; evaluation of drainage layers as structural layers; lime-stabilized sand subbases under bitumen; design and rehabilitation procedures for concrete roads; lightly-cemented base pavements; identification and evaluation of cost-effective rehabilitation techniques; evaluation of labour-intensive construction methods; testing various asphalt base pavements and improving the design, analysis and understanding of the behaviour of such pavement types; porous asphalt

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Ben

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Gautrans & SANRAL Combined

Breadth of benefitsMaterials/methodsdevelopment of a new large-

stone mix design method; use of modified binders in mixes; in situ recycling of materials (using cement, lime, foamed bitumen and bitumen emulsion); block paving (masonry and concrete); coarse power station generator ash; roller compacted concrete; slag; bitumen-rubber; waterboundmacadam; recycled asphalt base; upgrading of gravel roads; marginal natural aggregates with various additives; high quality granular bases; evaluation of drainage layers as structural layers; lime-stabilized sand subbases under bitumen; design and rehabilitation procedures for concrete roads; lightly-cemented base pavements; identification and evaluation of cost-effective rehabilitation techniques; evaluation of labour-intensive construction methods; testing various asphalt base pavements and improving the design, analysis and understanding of the behaviour of such pavement types; porous asphalt

Breadth of benefits

Materials/methodsdevelopment of a new large-stone mix design method; use of modified binders in mixes; in situ recycling of materials (using cement, lime, foamed bitumen and bitumen emulsion); block paving (masonry and concrete); coarse power station generator ash; roller compacted concrete; slag; bitumen-rubber; waterboundmacadam; recycled asphalt base; upgrading of gravel roads; marginal natural aggregates with various additives; high quality granular bases; evaluation of drainage layers as structural layers; lime-stabilized sand subbases under bitumen; design and rehabilitation procedures for concrete roads; lightly-cemented base pavements; identification and evaluation of cost-effective rehabilitation techniques; evaluation of labour-intensive construction methods; testing various asphalt base pavements and improving the design, analysis and understanding of the behaviour of such pavement types

Breadth of benefits

Materials/methodsdevelopment of a new large-stone mix design method; use of modified binders in mixes; in situ recycling of materials (using cement, lime, foamed bitumen and bitumen emulsion); block paving (masonry and concrete); coarse power station generator ash; roller compacted concrete; slag; bitumen-rubber; waterboundmacadam; recycled asphalt base; upgrading of gravel roads; marginal natural aggregates with various additives; high quality granular bases; evaluation of drainage layers as structural layers; lime-stabilized sand subbases under bitumen; design and rehabilitation procedures for concrete roads; lightly-cemented base pavements; identification and evaluation of cost-effective rehabilitation techniques; evaluation of labour-intensive construction methods; testing various asphalt base pavements and improving the design, analysis and understanding of the behaviour of such pavement types

Benefits (in a nutshell)• Better understanding and modeling:

• minimizes under design• pre-mature failures prevented

• minimizes over design• most cost-effective solution

- Fill the important gap between lab designs and true field pavement behaviour

• Allows better (optimal) use of funds and natural resources

Limitations of HVS Testing

• Difficult to simulate the effect of the environment on a pavement structure • Rainfall patterns• Seasonal temperature variations• Radiation

• Difficult to measure the long-term impact of changing water tables, rainfall run-off, freeze & thaw cycles in a short period of time

• The rate at which asphalt age with time

• Moisture sensitively

In summary its difficult to simulate 20 years ofenvironmental damage during a short period ofTime (+ - 3 months)

Limitations of HVS Testing

Loading

• Dynamic effects of true traffic at speed

• Axle hop• time of loading (speed) • rest periods (axle configurations and density of

traffic)

• Shear forces

• Steep downhill travel• Sharp turning movements• Stopping and acceleration at intersections)

HVS test planningEach test is designed to address theTesting objectives of that particular test

Examples:

• Determine fatigue behaviour• Test at ambient or lower than normal temperatures

• Determine rutting resistance• Test at elevated temperatures

• Determine effectiveness of prevention of water penetration

• Spray water on surface during testing

• Comparison between 2 alternativepavement structures• Duplicate testing plan

with no variation

HVS test planningTo evaluate the performance of pavement structuresthere are may variables to look at

• Loading regime• Standard axle load or higher

• Temperature• Ambient, cooler or hotter

• Wet or Dry testing• Local conditions, adding water, watering

schedule (how much and frequency)

• HVS related variables• Uni- or Bi-directional trafficking• Wheel speed• Wandering or Channelised trafficking• Constant or dynamic loading• Tyre pressure & wheel types

HVS test planningInstrumentation

• Delfections• Surface, in-depth, FWD, LWD

• Permanent Deformation• Rutting & in-depth

• Crack detection and visual surveys• Bottom-up, Top-down, reflective, etc• Surface distress

• Joint faulting, pumping

• Temperatures• Air, surface & in depth

• Environment• Rain, wind, radiation, temperatures

Conclusions• HVS is used in verifying laboratory and empirical derived designs

•Bridge the gap between laboratory & computer designs and real life pavement behaviour

•Quick assessment of various alternatives to pick most cost-effective one

•Assessment of in material behaviour in a composite true life structure under loading