COnstruction with UnboundRoadAGgregates in Europe

OVERVIEW

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• Objectives of COURAGE

• Participation in the project

• Work Package Activities

• Key Findings of Technical Work Packages

Work Package 2 - Mechanical Characterisation of UGMs

Work Package 3 - Variability of In-situ Condition

Work Package 4 - Modelling of Pavement Structures

Work Package 5 - Dissemination

COURAGE project aims to:

• extend the understanding of the mechanical behaviour of unbound granular materials used in pavements.

• characterise material behaviour in a manner suitable for application in pavement design for performance prediction (data for mechanistic design, develop appropriate models).

• attempt to validate laboratory data with measured pavement performance data (using lab. test data in computer model of pavement ---> check strains determined from analysis with those measured in field).

• apply knowledge to develop better materials and methods of use.

• findings for European pavement design and maintenance personnel.2

COURAGE OBJECTIVES

The partners and associate partners in COURAGE are:

3ie, 12 participants from 9 EU countries, ECU532,000 (approx. £373,000)

COURAGE PARTICIPANTS

Coordinator

WORK PACKAGE ACTIVITIES

4

The activities of COURAGE:

• WP1 - project management and co-ordination.

• WP2 - laboratory testing with some larger scale testing. simple testing - conventional and unconventional (eg. shape tests and

attrition by gyratory compaction). fundamental testing - more complex (eg. repeated load triaxial). simulative testing (eg. wheel tracking on a small-scale pavement).

• WP3 - collection, comprehension & prediction of in-situ conditions

study in-situ variability in pavements due to climate, topography, etc

The activities of the COURAGE:

• WP4 - material behaviour patterns model and classify materials. conduct full-scale pavement tests (use modelled material lab. test data in

pavement analysis computer models to predict performance - strains).

• WP5 - liaison & dissemination with technical experts outside of the project (e.g. AMADEUS, COST 337) technical evaluation and dissemination of the whole project's work.

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WORK PACKAGE ACTIVITIES (cont) ….

of the Technical Work Packages …….

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KEY FINDINGS

Aim:• to define tests and “standardise” test procedures for determining key

performance properties of unbound granular materials.• compare the results of these “complex” tests (eg. RLT) with those

of simpler tests (Static TXL test).• assess a number of granular materials, representative of those used

in different European countries. Rank these materials.

Why do we need to know this?• to adopt a systematic approach to determining key properties.• to obtain data for:

material performance comparisons (durability and modulus or strain with conditions ….. density, MC, geology and grading)

interpretation using material models use in full-scale pavement analysis / modelling in WP4

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Work Package 2

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In the past anticipated granular material performance has relied heavily upon a product's conformance with standard classification tests, eg:

• Particle Size Distribution (Grading) • Plasticity Limits (PI, LL, Linear Shrinkage)• Los Angeles Value

Perhaps other supplementary tests have also been used:• Washington Degradation• Texas Ball Mill• 10% Fines

Pavement field control tests used, eg. field dry density, moisture content

a number of pavement failures have resulted over the years

Background for WP2

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However, it is recognised that pavement performance is strongly controlled by the following conditions / factors:

• Stresses generated in the pavement due to traffic loadings• Material state of density, moisture content (or degree of saturation) -----------------------------------------------------------------------------------• Stiffness of materials under dynamic loading• Permanent strain of the materials under dynamic loading• Bearing strength of the materials under static loading• Durability of the materials• Permeability of the materials

3. - 7. are Material Properties which affect the ability of a material to perform in the pavement under the state conditions of 1. and 2.

Background for WP2

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Characterising these mechanisms has lead to the development of specialised testing systems (eg, repeated load triaxial, RLT) and procedures to better understand material performance by simulating the action of pavement loading.

Asphalt

Basecourse 1

Subgrade

Basecourse 2

Subbase

Surface Wheel Load

STRESSES APPLIED TO A MATERIAL ELEMENT IN THE PAVEMENT

E1

E2

E3

E4

E5

E6

Simple tests• The simple, empirically-based classification tests were

found to aid in material quality assessment, but failed to clearly indicate overall material quality.

Repeated Load Triaxial (RLT) test• Unbound Granular Materials (UGMs) were very sensitive to

changes in moisture content for a particular grading …...

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Findings …….

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PERMANENT AXIAL STRAIN RESULTSGRANITE MATERIAL WITH 10% FINES

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0 2500 5000 7500 10000 12500 15000 17500 20000

CYCLES

1p

-

1p

(1

00

) x 1

0-4

DDR=96.8%, RMC=43.9%

DDR=97%, RMC=70.9%

DDR=97%, RMC=75.3%

HIGH STRAIN SUSCEPTIBILITY

MODERATE STRAIN SUSCEPTIBILITY

LOW STRAIN SUSCEPTIBILITY

Example ….

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Repeated Load Triaxial (RLT) test• Permanent deformation characteristics of different UGMs

found in the wheel tracking tests were comparable with those determined by RLT testing ……..

• Marginal-type materials could not support the high stress loadings applied in the present draft of the CEN RLT Method A. Only, high quality basecourse-type materials will be able to be assessed at the preconditioning and resilient modulus stress stage paths currently presented in the CEN procedure.

Wheel Tracking (WT) test• For a very thinly surfaced unbound granular pavement, the

wheel tracking tests showed between 73 to 95% of the total layer permanent deformation resulted in the upper half of the basecourse layer

Findings …….

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PERMANENT STRAIN RATE RESULTS

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RELATIVE MOISTURE CONTENT (% of OMC)

PE

RM

AN

EN

T S

TR

AIN

RA

TE

PA

RA

ME

TE

R

d p

/dN

x 1

0-5

(%

/cyc

le)

Gneiss, Control GradingGranite, Control GradingLimestone, Control GradingUK RCC&A Supply GradingGneiss, WT testGranite, WT testLimestone, WT test

measured at 3000 cycles

FAILED

HIGH STRAIN SUSCEPTIBILITY

LOW STRAIN SUSCEPTIBILITY

Aim:to study variability of in-situ conditions in pavements (surveya number of trial pavements in various countries), in particular:• key aspects are temperature, rainfall, moisture changes within

pavement• aspects depend on climate, topography, etc

Why do we need to know this?• To investigate seasonal and transient variations in moisture within

pavement layers in time.

• to perform a sensitivity analysis on pavements to determine effect of material moisture changes (resilient modulus --> strains).

• in order that the results from WP2 (lab.testing) may be interpreted correctly as part of WP4 (modelling of pavements). 15

Work Package 3

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Seasonal Moisture VariabilityDifficulties were encountered in the installation and operation of TDR proves on some sites.

The evidence from the experimental sites suggests that more work is needed to develop equipment which can confidently monitor low moisture contents (<4%) in granular materials.

However, generally the measurement of moisture content using this method was very effective at the Test Sites……..

Findings …….

a) Measurement of Layer Thickness b) Sub-base TDR and Compaction Equipment

c) Measurement of Depth to TDR Probe d) Installation of TDR Probe in BasecourseLayer

(e) Datalogger and Solar Cell Mast and f) Compaction of Surface DressingInstrumented Layer Pit after Compaction of Unbound Layers

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TDR

INSTALLATION

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Seasonal Moisture VariabilityIn all European countries in which pavements were monitored for seasonal moisture changes it was observed that:

• the variation in all structural layers followed clearly defined seasonal variations, with the moisture content being the highest in autumn and spring ……..

Findings …….

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J J A S O N D J F M A M J J A

Gra

vim

etri

c m

oist

ure

con

t. [

%]

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Pre

cip

itat

ion

[m

m]

precipitation

Base course 2, D =15 cm

Subbase 1, D = 25 cm

Subbase 2, D = 45 cm

Lighter Rainfall period

Start of freeze/thew

Probe location depth

Gravimetric moisture content in a road in Iceland plotted along with the daily precipitation

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Heavy rainfall period

End of freeze/thaw

Freeze - Thaw Measurements in Icelandic road

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10'98 11'98 12'98 1'99 2'99 3'99 4'99 5'99

Month

Dep

th (

cm)

Frost ThawFrost

Seasonal Moisture VariabilityIn all European countries in which pavements were monitored for seasonal moisture changes it was observed that:

• moisture variations between 40% to 90%+ of mod. Proctor OMC could occur in different pavement layers during the course of a year, viz:• Finland, Site FI.1• base 1 layer, RMC = 42% to 81%• base 2 layer, RMC = 35% to 98%• sub-base layer, RMC = 122% to 151%

• France, (test track)• base layer, RMC = 42% to 98%

• Iceland, Sites IS.1-3• base 2 layer, RMC = 67% to 133% stand. Proctor OMC• sub-base 1 layer, RMC = 44% to 131% stand. Proctor OMC• sub-base 2 layer, RMC = 54% to 119% of standard Proctor OMC

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Findings …….

Seasonal Moisture VariabilityIn all European countries in which pavements were monitored for seasonal moisture changes it was observed that:

• moisture variations in different pavement layers during the course of a year ….. continued, viz:• Ireland, Site EI.1-2• base layer, RMC = 43% to 68%• sub-base layer, RMC = 43% to 68%

•Portugal, Site PT.1• sub-base layer, RMC = 27% to 97%

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Findings …….

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Seasonal Moisture VariabilityThrough monitoring two road sections in Finland, it was found that:

• pavement structures through cuttings yield a moisture content slightly higher, but with a lower variation, compared to pavement structures founded on an embankment.

• for structures through cuttings, water has the opportunity to flow into the pavement layers particularly if deep side drains are not installed

Findings …….

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Seasonal Moisture VariabilityRoad construction aspects to be considered include the:

• provision of an adequate depth of impervious bituminous surfacing and a sufficiently wide "hard" shoulder, with the same surfacing as the carriageway, to reduce variations in moisture content in unbound base and sub-base layers ……..

• Formation and taping of the shoulder of the road to prevent “drainage channels” forming next to the seal ……..

Findings …….

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3m wide “hard” shoulder at Site E1.3 in Ireland

Inadequate shoulder formation at Site in Iceland …. “drainage channel” adjacent to seal

3m wide “hard” shoulder

Aim:to analyse Project data/outcomes, in particular:• material models for stress-strain behaviour (Boyce, Dresden)• examine data for instrumented full-scale pavements• compare strain predictions from computer modelled pavements (using

material models) with measured strains in the pavement• examine modelling in detail (validity, influence of MC, etc)

Outputs?• information regarding material/pavement performance from trials• evaluate some actual pavements using different model techniques (linear

elastic, non-linear elastic, FE) ---> suggest merit of different approaches

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Work Package 4

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Dep

th (c

m)

Direction of the truck mouvement (x-x)

Vertical displacement (strain) transducers, GM

Vertical displacement (strain) transducers, SG

Tensiometers (suction) in GM & SG

Vertical pressure transducer, SG

Long. & transv. strain gauges, BM

Thermocouples (temp), BM

Full-scale experiment: typical pavement structure and instrumentation

86mm

430mm

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Bituminous mat.

Unbound Granular mat.

Subgrade mat.

analytical approaches being used for modelling pavements:

(1) all materials are linear elastic

(2) bit. layer linear elastic, GM non-linear elastic (Boyce), SG linear elastic

(3) bit. layer linear elastic, GM non-linear elastic (Boyce), SG non-linear elastic (Boyce)

(4) bit. layer visco-elastic, GM non-linear elastic (Boyce), SG non-linear elastic (Boyce)

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Full-scale pavement loading experiment: the LCPC site

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Pavement ModellingAn intermediate thickness of the bituminous layer (85mm) indicates:

a "limited" non-linear, load-dependent response of the flexible pavement (which can be further limited by cold test conditions causing stiffening of the bituminous layer).

a strong strain measurement dependence on the loading speed for speeds up to 40km/h

A thick bituminous layer (295mm) ) indicates: a a very linear response of the pavement to different

levels of load a strain measurement dependence on the loading

speed for very low speeds up to 15km/h

Findings …….

Aim:to analyse Project data/outcomes, in particular:• analysis of all project information (broad picture, key findings)• cost-benefit analysis (factors include pavement material properties,

traffic loadings, pavement life [modelling], material costs)• links with other projects (eg. COST337, AMADEUS, ALT-MAT, etc)• strong dissemination mechanisms

Outputs?• present COURAGE findings (reports, seminar UNBAR, papers, etc).• WWW interface for dissemination.

http://www.civeng.nottingham.ac.uk/courage/• design procedure for prediction of pavement performance based on

laboratory data.• draft of design and practice guide for material usage in pavements. 30

Work Package 5