The aggregate base is less sensitive to moisture than the subgrade and it separates the pavement further from the subgrade. Regardless of the SN required, a buildup that includes an aggregate base (Item 304) will generally provide better performance than an asphalt-on-subgrade buildup. 403 Typical Section and Buildup Considerations 403.1 Typical Section Design More common is to use the same thickness as the mainline or reduce the mainline thickness by 1 inch (25 mm). If traffic and soils data is available, ramps, collector-distributor lanes, directional roadways, etc., may be designed individually. An example flexible pavement design is provided in Figure 402-1. Structural number (SN) is determined using the nomographs found in Figures 402-2 and 402-3.
402 Structural Number DeterminationĪll of the design input information is required prior to determination of design thickness. Structural coefficients for ODOT asphalt concrete material specifications are found in Figure 401-1. Structural coefficient is the only new parameter. Serviceability, traffic loading (ESAL), subgrade stiffness (Mr), reliability and overall standard deviation have all been discussed in Section 200. 401 Design Parametersįlexible pavement design is based on relatively few input parameters. The Construction Administration Manual of Procedures published by the Office of Construction Administration contains additional information on flexible pavement and proper construction practices. Alterations to ODOT's Construction and Material Specifications (C&MS) for asphalt concrete may require adjustments to the procedures described herein.
Once the structural number is determined, the flexible buildup is determined by using the appropriate structural coefficient for ODOT specification materials. Flexible pavements can be constructed with Marshall mix designs, Superpave mix designs, stone ma trix mixes, or legacy ODOT mixes however, regardless of the mix design method used, the ODOT/AASHTO method of pavement design calculates the same required structural number. The structural number is a regression coefficient expressing the structural strength of a pavement required for given combinations of soil support (Mr), traffic loading, and terminal serviceability. Published: Janu400 Flexible Pavement Design 400.1 Introductionįlexible pavement design is based on the concept of structural number.
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