Estimate your potential savings when using geosynthetics for new or existing flexible pavement applications
Select Your Application
In flexible pavement design, a structural number can be assigned to dense graded asphalt, aggregate base, subgrade, and geosynthetics such as geogrid, each contributing to the overall performance and expected design life of the pavement.
Input your project's region and size to determine optimal cross sections for unreinforced and geogrid-reinforced solutions when considering a heavy duty pavement application.
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Design parameters
Required ESALs = 700,000+
HMA Layer 1
Coefficient = 0.44
HMA Layer 2
Coefficient = 0.42
Aggregate Base
Coefficient = 0.14
Drainage Factor = 1
Subgrade
Resilient modulus = 5000 psi (stiff)
Reliability = 95%
Standard deviation = .45
Serviceability Initial = 4.2
Terminal = 2
Solve for the estimated amount of asphalt required to rehabilitate a typical principal arterial section.
Rehabilitation is a necessary treatment that any pavement structure has to experience periodically during its structural life. A road agency on average typically gets 15 years of life from their overlays on Principal Arterials. Experience has shown that there are four design conditions that if present on a project each of which will incrementally reduce the expected overlay life. Typically if two or more of these conditions exist on a project, the use of an interlayer becomes a cost effectve solution to not only achieve the desired overlay life, but in many cases helps exceed it.
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Agencies typically perform 1.5 to 2" thick mill and overlays as standard rehabilitation best practice. All paving fabrics, paving mats and composite grids can be installed on the milled surface prior to the new overlay, without needing to increase the mill and overlay thickness, allowing the agency to keep to best practice. A 2" minimum thickness was selected, according to best practice, ensuring enough asphalt to mill and replace 1.5" without disrupting the previously installed interlayer or base material upon the following rehabilitation cycle.
See references below for asphalt equivalent thickness calculations relative to additional performance by design condition selected:
Poor Draining Subgrade: FHWA, Geosynthetic Design & Construction Guidelines, NHI Course No. 132013, FHWA, FHWA NHI-07-092, August 2008
High Truck Count (> 5 %): A Simplified Computer Model for Grid Reinforced Asphalt Overlays, NH Thom, University of Nottingham, UK, 2007
No Crack Sealing is Performed Annually: FHWA, Geosynthetic Design & Construction Guidelines, NHI Course No. 132013, FHWA, FHWA NHI-07-092, Agust 2008
Structural Distresses are Present: A Simplified Computer Model for Grid Reinforced Asphalt Overlays, NH Thom, University of Nottingham, UK, 2007
Select All Design Conditions That Apply
Low permeability soils such as clays, that are water sensitive
Where the truck traffic makes up more than 5% of the AADT
If no crack sealing has been performed on the existing pavement, then it is unlikley to be crack filled in the future
If there are patches, aligator cracking (fatigue), or wide subsoil cracks, then structural distress is considered to be present
Unreinforced
2 layers of dense graded HMA with a total thickness of 5", furnished and placed over 12" of aggregate base on stabilized subgrade.
Dense Graded Asphalt
$11.30/SY-in
Aggregate Base
$11.30/SY-in
Total Installed Cost
$6,610
Service Life
704,100 ESALs
Unreinforced:
$0 Saved
0% Savings
Reinforced
2.5" of dense graded HMA furnished and placed over a mechanically stabilized layer (MSL) consisting of 12” of aggregate base and NX750 geogrid on stabilized subgrade.
Dense Graded Asphalt
$11.30/SY-in
Aggregate Base
$11.30/SY-in
Geogrid
$11.30/SY
Total Installed Cost
6,610
Service Life
862,800 ESALs
Reinforced:
$790 Saved
45% Savings
Based on your design condition selections, interlayers may not be required to achieve your maximum desired design life for your overlay. This being the case, we recommend reaching out to a GEO Pro to verify the conclusion. Explore other potential cost saving solutions, such as paving fabrics, and request a free project evaluation.
Take the next steps by getting in touch with one of our GEO Pros. We are excited to understand how we can help you. Send us a request, and we will be with you shortly.