1. Tensar TriAx TX8 Geogrid
Full-Scale Accelerated Testing of Multi-axial Geogrid Stabilized Flexible Pavements Constructed over Very Stiff Soils
Research Organization
US Army Corps of Engineers
Engineer Research and Development Center
Sections Tested/Compared
4 inches (102 mm) HMA over 8 inches (203 mm) base (control)
3 inches (76 mm) HMA over 6 inches (152 mm) base over TX5
3 inches (76 mm) HMA over 6 inches (152 mm) base over TX8
Testing Conducted
Thickness Validation & Material Characterization
Instrumentation of sections
Pavement Characterization (post construction)
HVS-A Traffic testing, FWD analysis (811,200 ESALs)
Post trafficking forensics (in-field CBR, rutting of layers,…)
500,000 ESALs
45,971 dump trucks
81,928 buses
425,000,000 cars
811,200 ESALs
74,583 dump trucks
132,920 buses
689,520,000 cars
Key Findings
After 800,000+ ESALs, thinner TriAx stabilized sections, over stiff subgrade soils, had less than half as much rutting as the control.
Structural benefits of TriAx exceeded SP4Pro design values.
Estimates show TriAx provides ~16% savings in construction costs, ~19-25% improvement in performance (>60% improvement in this testing) and a savings in time of ~5.5 days per lane mile.
This slide presentation provides an overview of recent research conducted by the US Army Corps of Engineers at the US Army Engineering Research and Development Center. This testing is different from many previous studies on the use of geogrids in roadway applications. Most previous studies have been performed on unpaved sections over soft soils, or on paved section over soft soils. This recent testing was performed over stiff to very stiff subgrade soils. Additionally, trafficking for this study exceeded 800,000 ESALs.
Finding from this study showed that Tensar TX geogrids could reduce asphalt by 25%, and aggregate base thicknesses by 25% while still improving pavement performance over stiff soils by approximately 62% and reducing deformation by up to 44%. Values used within Tensar’s 3rd party reviewed design software were also shown to be conservative.
Control Section
Tensar TriAx TX8 Geogrid

2. Full-Scale Accelerated Testing of Multi-axial Geogrid Stabilized Flexible Pavements Constructed over Very Stiff Soils
US Army Corps of Engineers
Engineer Research and Development Center
Hanger 2

3. Full-Scale Accelerated Testing of Multi-axial Geogrid Stabilized Flexible Pavements Constructed over Very Stiff Soils
Objectives of Testing
Provide performance data of paved sections comparing Tensar TriAx geogrids to conventional methods over very stiff soils.
Compare a thicker asphalt pavement to thinner stabilized asphalt pavement with a TriAx stabilized base.
Record pavement response data in order to verify Tensar’s mechanistic models currently available on the market.
Verify SpectraPave4Pro design values.

4. Tensar TriAx TX5 Geogrid Tensar TriAx TX8 Geogrid
Full-Scale Accelerated Testing of Multi-axial Geogrid Stabilized Flexible Pavements Constructed over Very Stiff Soils
Scope
Construction, instrumentation and trafficking of test sections with TriAx stabilized bases and compare them to a control section.
Testing to be conducted using highly controlled and monitored Accelerated Pavement Testing (APT) to gather response data, limit the risk of variability and ensure proper comparisons.
Control Section
(Unstabilized)
Tensar TriAx TX5 Geogrid
Tensar TriAx TX8 Geogrid

5. Tensar TriAx TX5 Geogrid Tensar TriAx TX8 Geogrid
Full-Scale Accelerated Testing of Multi-axial Geogrid Stabilized Flexible Pavements Constructed over Very Stiff Soils
TriAx Products
Standard Aperture (Opening) Size
Smaller Aperture Size Designed for D50<= 22mm
Tensar TriAx TX5 Geogrid
Tensar TriAx TX8 Geogrid

6. Test Section Development
Full-Scale Accelerated Testing of Multi-axial Geogrid Stabilized Flexible Pavements Constructed over Very Stiff Soils
Test Section Development
Test sections were 10’ wide by 50’ long.
Sections were developed following guidelines outlined by NCHRP Report 512 – with high Quality Assurance and Quality Control for subgrade prep, base placement, instrumentation, climatic monitoring.
Testing of these section included the construction, instrumentation and trafficking of TriAx stabilized bases and compare them to a control section. Testing was conducted using highly controlled and monitored Accelerated Pavement Testing (APT) to gather response data, limit the risk of variability and ensure proper comparisons. APT testing is much more accurate than field testing, and procedures for this type are testing are outlined by the NCHRP in report APT evaluation requires significant oversight and adherence to proper tolerances. Much more detailed information on this testing, the NCHRP guidelines and quality controls, can be found in the NCHRP document.
To monitor TriAx benefits over more competent subgrade soils, this testing utilized moderate subgrade soils with a CBR of 6%.

7. Full-Scale Accelerated Testing of Multi-axial Geogrid Stabilized Flexible Pavements Constructed over Very Stiff Soils
Embedded video and video link on what is Accelerated Pavement Testing (APT) and why APT research is more accurate than standard field testing.

8. Tensar Workshop: Stabilisation
June/July 2015
Full-Scale Accelerated Testing of Multi-axial Geogrid Stabilized Flexible Pavements Constructed over Very Stiff Soils
Control
Total Deformation/Rutting
Design of pavements and trafficked areas using mechanical stabilisationCopyright (c) Tensar International Limited 2015

9. Tensar Workshop: Stabilisation
June/July 2015
Full-Scale Accelerated Testing of Multi-axial Geogrid Stabilized Flexible Pavements Constructed over Very Stiff Soils
Control
TX5
Total Deformation/Rutting
Design of pavements and trafficked areas using mechanical stabilisationCopyright (c) Tensar International Limited 2015

10. Tensar Workshop: Stabilisation
June/July 2015
Full-Scale Accelerated Testing of Multi-axial Geogrid Stabilized Flexible Pavements Constructed over Very Stiff Soils
Control
TX5
TX8
Total Deformation/Rutting
Design of pavements and trafficked areas using mechanical stabilisationCopyright (c) Tensar International Limited 2015

11. Tensar TriAx TX5 Geogrid Tensar TriAx TX8 Geogrid
Full-Scale Accelerated Testing of Multi-axial Geogrid Stabilized Flexible Pavements Constructed over Very Stiff Soils
Based on 0.3 inches total surface deformation
220,000 ESALs
187,000,000 cars
36,048 buses
20,227 dump trucks
811,200 ESALs
689,520,000 cars
132,920 buses
74,583 dump trucks
1,050,000 ESALs
892,500,000 cars
172,048 buses
96,539 dump trucks
Tensar TriAx TX5 Geogrid
Tensar TriAx TX8 Geogrid
Control Section
* Values Extrapolated. TX8 section never reached 0.31 inches total deformation

12. Tensar TriAx TX5 Geogrid Tensar TriAx TX8 Geogrid
Full-Scale Accelerated Testing of Multi-axial Geogrid Stabilized Flexible Pavements Constructed over Very Stiff Soils
Asphalt
$65/ton
Base
$18/cy
Excavation
$5/cy
Cost/Value (SP4 Modeling)
Control Section
Tensar TriAx TX5 Geogrid
Tensar TriAx TX8 Geogrid
495 per lm
$23.31 per sy
281,000 ESALs
$19.48 per sy
371 per lm
266,000 ESALs
$19.63 per sy
371 per lm
224,000 ESALs
5.5 days/lm
5.5 days/lm
The newly updated SP4-Pro software utilizes this testing and allows for design with both TX5 and TX8. It allows a user to look at and compare options. Values used within SP4-Pro are conservative and provide values below what were found during this and other phase of APT testing. In comparing the three-section tested in this study, and making some assumptions on asphalt, base rock and excavation pricing, the following cost and associated values can be seen. There are some significant initial construction cost benefits, with savings from 15.8 – 16.4%. The number of trucks traveling over existing infrastructure to service a project can be reduced by 25%. The pavement life can be improved from 19-25%. And the amount of time to construct a project can be significantly decreased by approximately 5 days per lane mile. This translates into additional benefits and costs such as reduced safety concerns, user costs and environmental costs.
Dump trucks
Cost to Construct
Dump trucks
Cost to Construct
Life
Life
Time Savings
Cost to Construct
Dump trucks
Life
Time Savings
16.4% Reduction
25% Reduction
19% Increase
15.8% Reduction
25% Reduction
25% Increase

13. Full-Scale Accelerated Testing of Multi-axial Geogrid Stabilized Flexible Pavements Constructed over Very Stiff Soils
Summary of Testing
TriAx stabilized sections, constructed with 25% less asphalt and base rock, allowed for significantly greater traffic and less deformation than a thicker control section.
TriAx stabilized sections apply to pavements constructed over competent subgrades, not only in areas of soft soils.
Estimates show TriAx provides ~16% savings in construction costs, ~19-25% improvement in performance and a savings in time of ~5.5 days per lane mile.
“…incorporation of a multi-axial geogrid in a flexible pavement base course provides a significant structural benefit.”
-- Corps 2017

14. 800-TENSAR-1 TensarCorp.com