Details:

Creators:
Wu, Zhong ; Gaspard, Kevin
Wu, Zhong ; Gaspard, Kevin Less -
Corporate Creators:
Louisiana Transportation Research Center
Corporate Contributors:
Louisiana. Dept. of Transportation and Development ; United States. Federal Highway Administration
Louisiana. Dept. of Transportation and Development ; United States. Federal Highway Administration Less -
Subject/TRT Terms:
[+]
Flexible Pavements Overlays (Pavements) Pavements, Flexible--Louisiana Pavements--Overlays Pavements--Testing
Publication/ Report Number:
FHWA/LA.08/454
Resource Type:
Tech Report
Geographical Coverage:
Louisiana
Edition:
Final report; Mar. 2006-Dec. 2008.
Corporate Publisher:
Louisiana Transportation Research Center
Abstract:
The current Louisiana Department of Transportation and Development (LADOTD) overlay thickness design method follows the “Component

Analysis” procedure provided in the 1993 AASHTO pavement design guide. Since neither field nor laboratory tests are required by LADOTD for

this method, pavement engineers usually rely on a pre-assigned parish-based typical subgrade resilient modulus value and a set of assumed layer

coefficients for determining the effective structural number of an existing pavement in an overlay thickness design. This may lead to significant errors

in the designed overlay thickness results because the selected design parameters do not represent actual field conditions.

The objective of this research was to develop an overlay design method/procedure that is used for a structural overlay thickness design of flexible

pavement in Louisiana based upon (1) in-situ pavement conditions and (2) non destructive test (NDT) methods, specifically the falling weight

deflectometer (FWD) and/or Dynaflect.

Fifteen overlay rehabilitation projects were selected for this study. These projects were strategically located throughout Louisiana with different

traffic levels. At each selected project, NDT deflection tests including the falling weight deflectometer (FWD) and Dynaflect were performed at a

0.1-mile interval. For some of the selected projects, detailed condition survey data including cracking, rut depth, International Roughness Index (IRI),

mid-depth temperature, and pavement thickness was also collected. Six NDT-based overlay design methods were selected and used in the overlay

thickness design analysis. Results indicated that the 1993 AASHTO NDT procedure generally over estimated the effective structural number for the

existing asphalt pavements in Louisiana, which would result in an under-designed overlay thickness. On the other hand, other NDT methods (i.e.,

ROADHOG, Asphalt Institute MS-17, Louisiana 1980 Deflection method, ELMOD5, and EVERPAVE) were found inapplicable to the Louisiana

pavement conditions because all those methods rely on locally calibrated design parameters. Since further calibration of those NDT methods requires

additional testing resources and is also considered very time-consuming, a modified FWD deflection based overlay thickness design method was

proposed in this study. This method, based upon the Louisiana Pavement Evaluation Chart (a relation between Dynaflect deflections and the

structural number of existing pavements) and in-situ subgrade modulus, is deemed able to directly represent Louisiana’s pavement condition. The

cost/benefit analysis revealed that, as compared to the current LADOTD component analysis method, the proposed NDT-based overlay design

method would potentially save millions of dollars in the flexible pavement rehabilitation in Louisiana. Therefore, before full implementation of the

new Mechanistic-Empirical (M-E) pavement design method, the proposed NDT-based overlay design method is recommended for implementation by

LADOTD.


Format:
PDF
Collection(s):
US Transportation Collection
Main Document Checksum:
[+]
urn:sha256:da64fe4d00a9d289714ddf6187c52cd27b3148af10904ae78c3c9f9c9fe38353
Download URL:
https://rosap.ntl.bts.gov/view/dot/18544/dot_18544_DS1.pdf
File Type:

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