‘Characterisation of Granular Materials Rut Resistance’ Austroads project TT1819 Pavement Technology Program Andrew Papacostas (VicRoads) Austroads Project

‘Characterisation of Granular Materials Rut Resistance’

Austroads project TT1819Pavement Technology Program

Andrew Papacostas (VicRoads) Austroads Project Manager

Austroads workshop – Wellington– 4th December 2014

www.arrb.com.au Trusted advisor to road authorities for technical input and solutions2

Project objective

– The purpose of the project is to maximise the use of available materials in road base construction, and reduce road agency costs, by developing effective methods for evaluating the performance of unbound granular materials.

– Propose improved laboratory testing for rut resistance characterisation

– Identify key material performance parameters to further develop material specifications


Project TT1163 ‘Better basis for bases’ (Optimum Use of Granular Bases)

Project background


Development of a wheel-tracker for laboratory characterisation

Report AP-R360-10 (Austroads 2010)

Project background


Project backgroundProject TT1611 ‘Improved rut resistance characterisation’ (Austroads 2012)


Project background

Development of the wheel tracking

testing procedures specimen

preparation and sealing


TT1819 - Two Main Research Components

Laboratory Characterisation

– Wheel-tracking (WT)

– Repeated Load Triaxial Tests (RLT)

Accelerated Pavement

Austroads 2014 – Report AP-T267-14


Accelerated Pavement Testing Component

• Test site: Dandenong South – VIC• Indoor facility

• Experiments focused on granular base deformation


Pavements structure

Unbound granular base

Stiff & not deforming support

Cement treated crushed rock

Unbound granular base

300 mm

150 mm

Natural clay subgrade

Re-used granular materials

Stabilised clay including drainage

layer

150 mm

Sprayed seal


Base Characteristics

Material Sample No.

PI (wet prep.)

OMC* (%)

MDD* (t/m3)

Granite standard 2514 9 - 5 6.6 2.22

Hornfels standard 2515 6 – 2 5.6 2.30

Granite increased plasticity 2516 12 - 6 5.5 2.29

Hornfels increased plasticity 2517 9 - 8 6.6 2.30

* modified proctor compaction (AS 1289.5.2.1)


Pavements layout

• 4 lanes x 3 (12 m long test sites)

Lane no.

Material (20mm well-graded crushed rock)

1granite, low-plasticity

2hornfels, low-plasticity

3granite, increased plasticity

4hornfels increased plasticity


ALF trafficking program

• Forecast 1.5 years of pavement trafficking, this equates to about 2½ million loading cycles– 8,000 cycles per day– 5 days per week– 40 weeks operational per year

• 12 pavements– 4 materials– 3 replicates or different conditions

• Allows about 200,000 trafficking cycles per pavement


ALF loading conditions

Objective: compare WT lab performance vs ALF performance

– WT tests (average contact stress ≈ 600 kPa)

– ALF: dual-tyre loads (11 R22.5)

Applied loading conditions:

• dual wheel (11R22.5 truck tyre) under 40kN

• Load wandering ± 0.5 m according to a pseudo normal distribution


Wheel-tracking test for UGM• Data processing

5 profiles along the wheel-path

Number cycles

(-150, -75, 0, +75, +150 mm)


WT data: mean deformation & rut depth

Mean profile deformation (Calculated across the tyre nominal width)

Maximum rut depth(Mathematical data processing)


• Crushed hornfels (example)

Mean deformation

Maximum rut depth

Test terminated before 40,000 cycles


Moisture sensitivity: TT1163 materials

RhyoliteHornfelsLimestoneTuff


WT .vs. ALF performance comparison

• ALF performance data (load = 60 kN on dual-wheel)


WT .vs. ALF performance comparison

• ALF .vs. WT moisture conditions

HornfelsLimestone

Rhyolite

Tuff


Trafficking results

3600 Lane 1

Lane 2

Lane 3

Lane 4

3602


Effect of moisture on pavement deformation

4.7%

4.2%

3.5%

MC + 0.5%

MC – 0.7%

MC

~ 70% OMC

~ 60% OMC

~ 50% OMC


Laboratory Characterisation Component


– Main focus: Wheel-tracking

– Repeated Load Triaxial Tests


WT testing program

• Testing conditions– 4 ALF materials– For each material

• DD = ALF pavmt DD• MC = three levels (ALF MC)

• Similar program is planned under triaxial conditions – RLT (AGPT033)– Shear strength testing


Moisture sensitivity data

• Preliminary results


RLT preparation conditions

• Data collected – Australian & NZ context– International practice– Summary

– Definition of the preparation conditions • Compaction (modified proctor hammer)• Compaction moisture content

– MC < OMC vs OMC + dry-back

• Loading conditions– AGPT033 – Drained (undrained)


Overall objective (principle)


Wheel-tracking (WT)

Accelerated Pavement

Documents

‘Characterisation of Granular Materials Rut Resistance’ Austroads project TT1819 Pavement Technology Program Andrew Papacostas (VicRoads) Austroads Project