Pavement Management
Services
Pavement Testing & Consultancy Est 1981
Subgrade Lime Stabilisation
A Pragmatic Investigation into
Pavement Design, Field Performance
& Construction Quality Control.
Presentation Rundown
•
Introduction/Background
•
Stabilisation
–What is it?
•
Design
–How do we do it?
•
Investigation
–How we observed?
•
Results - What did we learn?
•
Conclusions
–For The Future…
Wirtgen-Group.com.au
Introduction/Background
•
2019 ICC commission the Rehabilitation design of Briggs Road, Ipswich (430m).
•
Industrial Collector Road Servicing Surrounding Industry and Sports Precinct.
•
Complete Urban Awarded the Contract &
PMS Subcontracted for Pavement Design.
•
Geotechnical Investigation & Lab Testing of pavement materials provided by council.
The Project…
The Pavement…
•
Pavement Failures, Rutting, Cracking, Extensive Patching, No Kerb & Channel or Pedestrian Facilities.
•
Subgrade:
•
Reasonable CBR
•
Reasonable DCP with Indication of Low strength
•
High/Very High Expansive Nature
•
High Moisture and In a Plastic State
•
Design for Low CBR and Highly Expansive
•
Existing Pavement Variable
–Low Quality Base
Introduction/Background
Stabilisation
What is it?
•
A Means of
Strengthening&
ModifyPavement Materials Properties.
• The simple act of Working or Kneading the Materials e.g. Compaction .
• Mechanical – Mixing Aggregates to Modify Grading Structure & Particle Interaction.
• Additives–
• Cement, Cement Blends
• Bituminous
• Lime
• Proprietary Products
• Plant orInsituMixed
Design
How Do We Do It?
Design
How Do We Do It?
Design Requirement Austroads method A Austroads method B DTMR Method Lime Content To Satisfy Lime Demand and
Achieve Target UCS
To Satisfy Lime Demand and Achieve Design CBR
To Satisfy Lime Demand and Achieve Target UCS Target Lab Strength UCS >1.0 - 2MPa (28 Day) CBR Satisfy Design CBR UCS 1.5MPa (28 Day)
Layer Mechanistic
Design Not Specific Modulus Subgrade
Dependent
Assigned vertical modulus at top of layer
Max Strength Not Specific 150MPa / 15% CBR 200MPa
Nominal Thickness Not Specific 200 - 300mm 250mm - 300mm (300mm
preferable)
• Austroads calculates the maximum vertical modulus based on the subgrade support given by:
• Method B and TMR both Sublayer into equi-thick layers
• TMR Adopt a Nominal 200MPa
Mechanistic Design Parameters
Investigation
How We Observed?
• PrimarilyFWDand Secondary DCPtesting for Comparison
• FWD Conducted at 5m Intervals staggered– DCP Every 10m
• Backcalculated & Used for Construction QA– Provisions for Deficiencies
• Tested Various Stages of Construction and Over Time*
• Included an Assessment of Different Amelioration Periods (ref paper)
X
Results
What Did we learn?
Layer modulus increased by factors between 2.8 and 4.1, after 48 hrsof Stabilisation (lowest 10thpercentile results)
The Austroads sublayer methodology was confirmed appropriate
*
The DTMR modulus (200MPa_) was readily Achievable, even with the Austorads Mix Design.
An unexplained reduction in modulus was noted on day 14
The removal of a 12hr Amelioration Period had Little Effect (54MPa) The FWD results of the natural subgrade correlated Very Well with theCBRResults and was Effective as a Quality Control Measure.
DCP Results Were Highly Variable
Conclusion
For the Future…
Austroads Design Modulus is Applicable (when using the Austroads Mix Design)
- The Average Can be Expected to be Higher (Safety Factor, Inconsistencies with Insitu Mixing) Caution using the CBR as an Indicator of Strength/Performance for Mix Design
- Subgrade50MPa(tested) = 200MPa (cap to 150MPa) therefore,
a CBR of15%would be required, results were90%at mix design phase - A CBR 6 times that of the design,to achievethe designmodulus
CBR x 10Correlation isInvalidfor Lime Stabilised Subgrades (As Is Granular Materials) AssestheUCSas well as CBR for AustroadsMethod B
Ameliorationperiod may be relievedfor Method B
Trent McDonald
tmcdonald@pavement.com.au Ph: (07) 5357 9841
M: (0403) 240 725
THANK YOU
Further Investigations? We’d like to hear from you…
• Very Poor Subgrades (CBR <2%)
• Hybrid Stabilisation - Different Blends
• Geogrid Vs. Stabilisation Vs. Replacement
• Foamed Bitumen
• Constriction QA
• Performance Monitoring
