Asphalt Concrete Overlay Design of Fractured JPCP

An Asphalt Concrete Overlay of fractured JPCP is a rehabilitation option considered in PMED.

For this AC overlay design type, the pre-overlay activity is fracturing existing PCC slabs. The objective of fracturing existing PCC slabs prior to AC overlay placement is to eliminate reflection of distresses such as cracking in the existing PCC into the AC overlay. This is done by fracturing the PCC slab in place into small fragments, while retaining good interlock between the fractured particles. In effect the integrity of the existing PCC slab is destroyed and replaced with a strong high-quality interlocked non-stabilized material.

PMED considers the effect of pre-overlay fracturing of the existing PCC slab through the selection of appropriate fractured PCC properties. PMED can be used to design and evaluate AC Overlays of Fractured JPCP.

General Design Inputs

An AC Overlay of Fractured JPCP pavement is a fractured JPCP pavement rehabilitated with a new AC surface.

The following options allow you to establish the basic parameters of your project.

Ways to Access this Interface

Open a new pavement project. The General Information area appears at the top-left corner of the Project Tab.

Figure 446: General Information

Populating the Inputs for this Interface

• Design type: Select Overlay

• Pavement type: Select AC over JPCP (fractured)

In addition to selecting Design and Pavement type, select values for the following basic design parameters:

• Design life (years): This control allows you to select from a list the period of time in years from AC overlay placement where the rehabilitated pavement is expected to perform adequately without significant loss of functional and structural integrity. Pavement performance is predicted over the design life beginning from the month the rehabilitated pavement is open to traffic.

• Base construction: This control allows you to select the month and year when the construction of existing JPCP was completed.

• Pavement construction: This control allows you to select the month and year when the AC overlay is scheduled to be placed.

• Traffic opening: This control allows you to select the month and year the rehabilitated pavement is scheduled to be open to traffic. PMED predicts pavement performance beginning from this month and year.

Performance Criteria

Performance verification forms the basis of the acceptance or rejection of a trial design evaluated using PMED. The design procedure is based on pavement performance, and therefore, the critical levels of pavement distresses that can be tolerated by the agency at the selected level of reliability needs to be specified by the user. If the simulation process shows the trial design produces excessive amount of distresses, then the trial design must be modified accordingly to produce a feasible design in the future trials.

The distress types considered in the design of an AC overlay of fractured pavement are total rutting (all layers and subgrade), AC rutting, load-related top-down cracking (longitudinal cracking in the wheel path) and bottom-up fatigue cracking (alligator cracking), and thermal cracking (transverse cracking). In addition, pavement smoothness is considered for performance verification and is characterized using the International Roughness Index (IRI).

Figure 447: Performance Criteria

Populating the Inputs in this Interface

This table allows you to define the limits of critical distresses and smoothness that can be tolerated by the agency at the specified reliability levels. This table has three columns:

• Performance Criteria: This column provides a list of performance indicators required to ensure that a pavement design will perform satisfactorily over its design life.

• Limit: This column allows you to define the threshold values of these performance indicators to evaluate the adequacy of a design.

• Reliability: This column allows you to define the probability at which the predicted distresses and smoothness will be less than the limits over the design period.

Note:
You can override the program defaults to enter project-specific threshold limits and reliability values representing agency policies. Refer to Chapter 8 of the AASHTO Manual of Practice for more guidance on selecting design criteria and reliability level.

• Initial IRI (in./mile): he limit control allows you to define the expected smoothness immediately after new pavement construction (expressed in terms of IRI). Initial IRI is a very important input as the time from initial construction to attaining threshold IRI value is very much dependent on the initial IRI obtained at the time of construction. Thus, the initial IRI value provided must be what is typically attained in the field. You can override the PMED default value of 63 in./mi to reflect agency policy and guidelines.

• Terminal IRI (in./mile): The limit and reliability controls for this criterion allow you to define the not-to-exceed limit for IRI at the end of the rehabilitation design life at a specified reliability level.

• AC top-down fatigue cracking (% lane area): The limit and reliability controls for this criterion allow you to define the not-to-exceed limit for surface initiated fatigue cracking at the end of the rehabilitation design life at a specified reliability level.

• AC bottom-up fatigue cracking (percent): The limit and reliability controls for this criterion controls allow you to define the not-to-exceed limit for bottom-initiated fatigue cracking at the end of the rehabilitation design life at a specified reliability level.

• AC thermal cracking (ft./mile): The limit and reliability controls for this criterion allow you to define the not-to-exceed limit for non-load related transverse cracking at the end of the rehabilitation design life at a specified reliability level.

• Permanent deformation - total pavement (in.): The limit and reliability controls for this criterion allow you to define the not-to-exceed limit for total rutting at the end of the rehabilitation design life at a specified reliability level. Total permanent deformation at the surface is the accumulation of the permanent deformation in all of the asphalt and unbound layers in the pavement system.

• Permanent deformation - AC only (in.): The limit and reliability controls for this criterion allow you to define the not-to-exceed limit for rutting contributed by the AC layers at the end of the rehabilitation design life at a specified reliability level.

Pavement Structure

This section explains adding additional layers to a pavement, editing the properties of those layers, and working with the pavement structure as a whole.

Asphalt Concrete

In PMED, the material types that fall under the following general definitions can be defined as an asphalt layer:

• Hot Mix Asphalt (HMA)
• Dense Graded
• Open Graded Asphalt
• Asphalt Stabilized Base Mixes
• Sand Asphalt Mixtures
• Stone Matrix Asphalt (SMA)
• Cold Mix Asphalt
• Central Plant Processed
• Cold In-Place Recycling

If a small portion of asphalt and/or emulsion is added to granular base materials, and can be produced at a plant or mixed in-place, this material should not be considered as an AC layer. If needed, it should be combined with the crushed stone base materials or considered as an unbound aggregate mixture.

The key materials inputs required for asphalt concrete layers are:

• Dynamic modulus of asphalt mixtures
• Rheological properties of asphalt binder (e.g. viscosity, penetration, complex modulus and phase angles)
• Creep compliance and indirect tensile strength
• Mix related and other properties (e.g. effective binder content, air voids, heat capacity, thermal conductivity)
• These inputs are required for predicting pavement responses, climatic analysis, asphalt aging as well as pavement performance.

Note:
For non-conventional mixtures, such as the Stone Matrix Asphalt or polymer-modified asphalt mixtures, it is recommended that you use laboratory-tested material properties. Levels 2 and 3 options for estimating dynamic modulus, indirect tensile strength and creep compliance properties provide reasonable results only for conventional Hot Mix Asphalt mixtures.

Interface

Figure 448: Asphalt Layer User Interface

Methods to Populate Inputs

There are two methods for entering data for the Asphalt Concrete layer:

• Manual entry
• Import from workspace library

Inputs

General Inputs

Thickness (inch, mm): This control allows you to define the thickness, in inches or millimeters, of the selected layer.

Mixture Volumetrics

• Unit weight (\(lb/ft^3\), \(kg/m^3\)): This control allows you to define the weight of the selected material in pounds per cubic foot.
• Effective binder content (%): This control allows you to define the effective binder content of the asphalt concrete mixture.
• Air Voids (%): This control allows you to define the percent volume of air voids in the as-constructed asphalt concrete pavement layer.
• Percent asphalt content by weight of mix (%): This control allows you to define the percent asphalt content by weight of mix (only used in the top-down cracking model). This input is only visible for the first asphalt layer in the user defined structure.
• Aggregate Gradation:: This control allows you to enter the asphalt mixture gradation and calculates the aggregate parameter for the top-down cracking model. A user defined aggregate gradation parameter can also be entered.The required aggregate gradation inputs are:
  • 3/4 inch (19 mm) sieve: This control allows you to define the cumulative amount of aggregate material (used in the asphalt mixture) that is passing on the 3/4 inch (19 mm) sieve.
  • 3/8 inch (9.5 mm) sieve: This control allows you to define the cumulative amount of aggregate material (used in the asphalt mixture) that is passing on the 3/8 inch (9.5 mm) sieve.
  • No. 4 (4.75 mm) sieve: This control allows you to define the cumulative amount of aggregate material (used in the asphalt mixture) that is passing on the #4 (4.75 mm) sieve.
  • No. 200 (0.075 mm) sieve: This control allows you to define the amount of aggregate material (used in the asphalt mixture) that is passing on the #200 (0.075 mm) inch sieve.
• Poisson’s ratio: This control allows you to define the Poisson’s ratio of the material in two ways: a constant value (Level 3) or calculate as a function of dynamic modulus (Level 2). Clicking the plus sign (+) to the left of this control presents the following options:
  • Is Poisson’s ratio calculated?: Select True to calculate Poisson’s ratio as a function of dynamic modulus. Select False to use a constant value.
  • Poisson’s ratio: This control allows you to define a constant value of Poisson’s ratio .This control is disabled when you select True.
  • Poisson’s ratio Parameter A: This control allows you to define the parameter A of the Poisson’s ratio model. You can override the default value of -1.63 to enter mixture-specific values. This control is disabled when you select False.
  • Poisson’s ratio Parameter B: This control allows you to define the parameter B of the Poisson’s ratio model. You can override the default value of 3.84E-06 to enter mixture-specific values. This control is disabled when you select False.

Note:
Parameters A and B are the empirical coefficients of the predictive model that defines Poisson’s ratio as a function of dynamic modulus, as described in the AASHTO Manual of Practice.

Mechanical Properties

Dynamic Modulus

Dynamic modulus input level: This control allows you to define the level of inputs for dynamic modulus of asphalt concrete material. Select one of the following options from the drop down menu:

Level 1: Selecting 1 gives you the option to input directly the laboratory tested dynamic modulus properties of the asphalt concrete mixture and laboratory tested asphalt binder properties.

Figure 449: Dynamic Modulus Level 1

• Select temperature level: This control allows you to define the number of test temperatures at which the dynamic modulus values is provided for a given mixture.
• Select frequency level: This control allows you to define the number of test frequencies at which the dynamic modulus values is provided for a given mixture.

Note:
PMED allows a minimum of 3 and a maximum of 8 temperature levels. It also allows a minimum of 3 and a maximum of 6 frequency levels. Inputs at 5 temperature and 4 frequency levels are recommended.

• Temperature (\(^\circ F\), \(^\circ C\)): This control allows you to define the temperature at which the dynamic modulus values were measured for a given mixture. You should enter at least one input value less than \(30^\circ F\) (\(-1^\circ C\)), another in the range of \(40\) to \(100^\circ F\) (\(4.44\) to \(37.78^\circ C\)), and the third input value higher than \(125^\circ F\) (\(51.67^\circ C\)).
• Frequency (Hz): This control defines the test frequency at which the dynamic modulus values were measured for a given mixture. You should enter at least one input value less than 1 Hz, two in the range of 1-10 Hz and the fourth input value higher than 10 Hz.

You can populate the cells within the dynamic modulus table provided with corresponding dynamic modulus values for the user-defined temperature and frequency levels.

PMED provides the following default temperatures and frequencies:

• US customary
  • 14, 40, 70, 100 and 130 \(^\circ F\)
  • 0.1, 1, 10 and 25 Hz.
• SI
  • -10, 4.44, 21.11, 37.78 and 54.54 \(^\circ C\)
  • 0.1, 1, 10 and 25 Hz.

Level 2: Selecting 2 gives you the option to derive dynamic modulus properties from laboratory tested asphalt binder properties and the aggregate gradation of the asphalt concrete mixture.

Level 3: Selecting 3 gives you the option to derive dynamic modulus properties from typical rheological properties of the asphalt binder grade you select and the aggregate gradation of the asphalt concrete mixture.

Figure 450: Dynamic Modulus Level 2 and 3

Note:
The model for determining frequency adjusted viscosity is research grade and not nationally calibrated, while the simple conversion model is nationally calibrated. This option is applicable only for Superpave binders at input levels 1 and 2.

Dynamic Modulus Predictive Model

Select HMA Estar predictive model: This control provides you the option for accounting the effects of loading frequencies when binder G* values are converted to viscosity values. Select True for frequency-adjusted viscosity estimates or False for simple conversion without frequency adjustments.

Reference Temperature

Reference temperature (\(^\circ F\), \(^\circ C\)): This control allows you to define a baseline temperature, in degrees Fahrenheit, for use in deriving the dynamic modulus mastercurve. The suggested value is \(70^\circ F\) (\(21.1^\circ C\).

Asphalt Binder Selection

Asphalt Binder: This control allows you to define the inputs of asphalt binder properties of asphalt concrete material. The controls in the drop down menu vary with the dynamic modulus input level you selected.

Note:
Once the dynamic modulus input level is selected, the program automatically defines the same input level for asphalt binder properties. Thus, a Level 1 dynamic modulus input selection will result in a Level 1 input selection for asphalt binder properties. Asphalt binder input level cannot be changed independent of the dynamic modulus input level.

Level 1:

SuperPave Performance Grade

Figure 451: Level 1 SuperPave Performance

• Temperature (\(^\circ F\), \(^\circ C\)): This control allows you to define the temperature at which the binder dynamic complex modulus, G*, and phase angle were measured for a given binder.
• Binder G (Pascal):* This control allows you to define the complex shear modulus of the asphalt binder, measured at the test temperature given in the above control.
• Phase angle (degree): This control allows you to define the phase angle measured at the given test temperature. You should enter at least three values in the above controls, though five is recommended.

Penetration or Viscosity Grade

Figure 452: Level 1 Penetration and Viscosity

• Softening point temperature at a viscosity of 13000 Poise: This control allows you to define the softening point temperature of the asphalt binder at a viscosity of 13000 Poise.
• Absolute viscosity of the binder at 140 F: This control allows you to define the absolute viscosity of the asphalt binder at a temperature of 140°F.
• Kinematic viscosity at 275 F in centistokes: This control allows you to define the kinematic viscosity of the asphalt binder at a temperature of 275°F.
• Specific gravity of asphalt binder at 77 F: This control allows you to define the specific gravity of the asphalt binder at a temperature of 77°F.
• Penetration (both temp and penetration value): This control allows you to define the both the temperature, in degrees Fahrenheit, and the corresponding penetration value of the asphalt binder.
• Brookfield viscosity (both temp and viscosity): This control allows you to define the both the temperature, in degrees Fahrenheit, and the corresponding viscosity value of the asphalt binder.

You must enter values for the softening point, specific gravity, absolute viscosity, and kinematic viscosity of the asphalt binder as a minimum. In addition, you may choose to provide either binder penetration or Brookfield viscosity properties or both. PMED allows you to enter penetration or viscosity values for up to six test temperatures.

Level 3:

The user first selects a binder grading system (radio buttons) and then selects a binder grade from the dropdown menu. (Once a binder grade is selected, the program assumes and displays the typical values of A-VTS parameters for that binder grade).

Figure 453: Level 3 SuperPave

Figure 454: Level 3 Penetration

Figure 455: Level 3 Viscosity

• Binder Grade Selection: This control allows you to define the binder grade type. Select one of the following options
  • Superpave Performance Grade: This control allows you to select an appropriate PG binder from the options provided by the binder type dropdown menu.
  • Viscosity Grade: This control allows you to select an appropriate viscosity- graded binder from the options provided by the binder type dropdown menu.
  • Penetration Grade: This control allows you to select an appropriate penetration-graded binder from the options provided by the binder type dropdown menu.
  • A: This control displays the intercept of the ASTM D2493 A-VTS relationship of the binder.
  • VTS: This control displays the slope of the ASTM D2493 A-VTS relationship of the binder.

Indirect tensile strength at 14 deg F: Indirect tensile strength at -10 deg C: This control allows you to define the indirect tensile strength of the asphalt concrete mixture at a temperature of -10˚C. You can enter a laboratory measured value (Levels 1 and 2) or allow the program to calculate a typical value (Level 3) based on statistical relationships with other AC inputs.

Figure 456: Level 1 IDT

Figure 457: Level 2 IDT

Figure 458: Level 3 IDT

Thermal

Figure 459: Asphalt Thermal

• Thermal conductivity (BTU/hr-ft-deg F): This control allows you to define the thermal conductivity of the asphalt concrete material. PMED provides a default value of 0.67.

• Heat capacity (BTU/lb-deg F): This control allows you to define the heat capacity of the asphalt concrete material. PMED provides a default value of 0.23.

• Thermal contraction: This control allows you to define the coefficient of thermal contraction of the AC mix in two ways: a direct entry of the coefficient or allow the program to compute as a function of thermal contraction coefficient of the aggregates. Clicking the sign () to the left of this control presents the following options:

• Is thermal contraction calculated?: Select True to calculate the mix contraction coefficient as a function of the aggregate contraction coefficient. Select False to directly enter the mix contraction coefficient.

• Mix coefficient of thermal contraction: This control allows you to directly enter the coefficient of thermal contraction of the AC mix. PMED provides a default value of 1.3E-05 in./in./˚F.

• Aggregate coefficient of thermal contraction: This control allows you to directly input the coefficient of thermal contraction of the aggregates. PMED provides a default value of 5.0 E-06 in./in./˚F.

Fractured PCC Layer

PMED considers three methods of fracturing existing pavement PCC as defined below:

• Rubblization: Applicable to all PCC slabs. Used for fracturing existing PCC slabs into pieces less than 12 inches reducing the existing PCC slab to a high-strength non-stabilized material. Rubblization is commonly applied to PCC layers with extensive deterioration (severe mid-slab cracks, faulting, spalling at cracks and joints, D-cracking, etc.).
• Crack and Seat: Applicable to PCC slabs. Used for fracturing the PCC slabs into pieces typically one to three feet in size.
• Break and Seat: Applicable to jointed reinforced concrete pavement (JRCP) slabs. Used for rupturing the reinforcing steel in JRCP across each crack and breaking its bond with the PCC.

Interface

Figure 460: PCC Fractured

Methods to Populate Inputs

There are two methods for entering data for the Portland Cement Concrete layer:

• Manual entry
• Import from workspace library

Inputs

General Inputs

• Layer thickness (in.): This control allows you to define the thickness of the fractured PCC layer.
• Unit weight (pcf): This control allows you to define the weight per unit volume of the fractured PCC material. PMED provides a default value of 150 pcf.
• Poisson’s ratio: This control allows you to define the Poisson’s ratio of the fractured PCC material. PMED provides a default value of 0.2.

Strength

• Elastic/resilient modulus (psi): This control allows you to define the required elastic/ resilient modulus value of fractured PCC materials. One method commonly used to estimate the elastic modulus of the fractured PCC pavement is to perform FWD deflection tests and backcalculate fractured PCC layer modulus from the deflection basins measured. This is mostly done on several similar projects to estimate typical values. Typical moduli values range from 150,000 to 1,000,000 psi for crack/seat and break/seat and 50,000 to 150,000 psi for rubblized PCC.

Thermal

• Thermal conductivity (BTU/hr-ft-deg F): This control allows you to define the thermal conductivity of the fractured PCC material. PMED provides a default value of 1.25 Btu/(ft)(hr)(˚F).
• Heat capacity (BTU/lb-deg F): This control allows you to define the heat capacity of the fractured PCC material. PMED provides a default value of 0.28 Btu/(lb)(˚F).

Chemically Stabilized Layer

The required inputs for a chemically stabilized layer can be broadly classified as general, strength, and thermal properties. Note that the strength properties required by PMED are different for flexible and rigid pavements.

The chemically stabilized materials include lean concrete, cement stabilized, open graded cement stabilized, soil cement, lime-cement-flyash, and lime treated materials.

You can use the following guidance to decide when a level of material stabilization is adequate to be considered as a chemically stabilized layer or not:

• Chemically stabilized materials that are “engineered” to provide long-term strength and durability should be considered as a chemically stabilized layer (e.g. cement treated, lean concrete, pozzolonic treated). Typically such layers are placed directly under the lowest asphalt layer.
• Lime and/or lime-fly ash stabilized soils could be considered a chemically stabilized layer, if these layers are engineered to provide structural support and have a sufficient amount of stabilizer mixed in with the soil.
• Lime and/or lime-fly ash stabilized soils could be also considered as a material layer that is insensitive to moisture and the resilient modulus or stiffness of these layers can be held constant over time.
• Aggregate or granular base materials treated with small amounts of chemical stabilizers to enhance constructability (e.g. lower the plasticity index, improve the strength) should not be considered as a chemically stabilized layer. They should be considered as an unbound material, and combined with those unbound layers, if necessary (e.g. soil cement). Typically such layers are placed deeper in the pavement structure.

Interface

Figure 461: Chemically Stabilized Layer

Methods to Populate Inputs

There are three methods for entering data for the Stabilized (Flexible) layer:

• Manual entry
• Import from workspace library

Inputs

General Inputs

• Layer thickness (inch,mm): This control allows you to define the thickness of the stabilized base layer.
• Poisson’s ratio: This control allows you to define the Poisson’s ratio of the chemically stabilized material. Values between 0.15 and 0.35 are typical for chemically stabilized materials.
• Unit weight (\(lb/ft^3\), \(kg/m^3\)): This control allows you to define the weight per unit volume of the stabilized base material. PMED provides a default value of 150 pcf.

Strength Properties

• Elastic/resilient modulus (psi): This control allows you to define the required elastic/ resilient modulus value of chemically stabilized materials.
• Minimum elastic/resilient modulus (psi): This control allows you to define the minimum modulus of chemically stabilized material that represents deteriorated condition under increased levels of fatigue damage. This input is required only for flexible pavements with a chemically stabilized layer placed directly under the AC layer. PMED will not display this control for other pavement types.
• Modulus of Rupture (psi): This control allows you to define the modulus of rupture of chemically stabilized material. The 28-day value is used for design. This input is required only for flexible pavements with a chemically stabilized layer placed directly under the AC layer. PMED will not display this control for other pavement types.

Note:
These inputs can be determined either through laboratory testing, correlations, or based on agency experience and historical records for levels 1, 2 and 3, respectively.

Thermal Properties

• Thermal conductivity (BTU/hr-ft-deg F): This control allows you to define the thermal conductivity of the chemically stabilized material. PMED provides a default value of 1.25 Btu/(ft)(hr)(˚F).
• Heat capacity (BTU/lb-deg F): This control allows you to define the heat capacity of the chemically stabilized material. PMED provides a default value of 0.28 Btu/(lb)(˚F).

Non-stabilized unbound base

Non-stabilized materials include AASHTO soil classes A-1 through A-3, as well as those commonly defined in practice as crushed stone, crushed gravel, river gravel, permeable aggregate, and cold recycled asphalt material (includes millings and in-place pulverized material).

Inputs required for non-stabilized materials include physical and engineering properties such as dry density, moisture content, hydraulic conductivity, specific gravity, soil-water characteristic curve (SWCC) parameters, classification properties, and the resilient modulus.

Interface

Figure 462: Unbound

Methods to Populate Inputs

There are two methods for entering data: - Manual entry - Import from workspace library

Inputs

General Inputs

• Layer thickness (in, mm): This control allows you to define the thickness of the selected layer.
• Poisson’s ratio: This control allows you to define the Poisson’s ratio of the unbound material. PMED provides a default value of 0.35.
• Coefficient of lateral earth pressure (k0): This control allows you to define the pressure that the unbound material exerts in the horizontal plane. PMED provides a default value of 0.5.

Resilient Modulus

Resilient Modulus (psi, MPa): This control allows you to define the level of inputs for resilient modulus of the unbound material. This control also allows you to define the resilient modulus or the other material properties that correlate with the resilient modulus. PMED displays the default value (Level 3) for the selected material class. Click on the Resilient Modulus control to modify the default value and/or input level.

• Input Level: This control allows you to define the level of inputs for the non-stabilized material. You can select one of the following options:
  • Level 1: PMED does not provide Level 1 inputs option for resilient modulus of non-stabilized materials.
  • Level 2: This option allows you to define the resilient modulus directly or using its correlations with soil index and strength properties. This level of input is considered as Level 2 in the AASHTO Manual of Practice.
  • Level 3: This option allows you to override the default resilient modulus value (Level 3) of the non-stabilized material.
• Analysis Types: These controls allow you to define how PMED accounts for seasonal variations (freezing, thawing and moisture) in the resilient modulus calculations. Select one of the following options:
  • Modify input values by temperature/moisture: This option allows you to define a single resilient modulus value. You can also input a single value of the selected soil index or strength property that is converted by PMED into a resilient modulus value. PMED incorporates the effects of seasonal variations on the single resilient modulus value you define.
  • Monthly representative values: This option allows you to define the resilient modulus throughout the year. You can input a single value of resilient modulus (or the selected soil index or strength property) for each month of a year. By selecting this option, you make PMED use the inputs you provide directly for seasonal variations without making internal adjustments. This option is available only for Level 2 inputs.
  • Annual representative values: This option allows you to define a fixed resilient modulus for an entire year. You can input a single value of resilient modulus (or the selected soil index or strength property) that is representative for an entire year. PMED does not incorporate the effects of seasonal variations on the single resilient modulus value you define.
• Correlation Methods to estimate Resilient Modulus: This control allows you to select how to estimate the resilient modulus using one of the following options:
  • Resilient modulus (psi, MPa)
  • California Bearing Ratio (CBR) (percent) R-value
  • Layer Coefficient-ai
  • Dynamic Cone Penetrometer (DCP) Penetration (in./blow, mm/blow)
  • Plasticity Index (PI) and Gradation (i.e., Percent Passing No. 200 (0.075mm) sieve)
• Input Entry Table: This control allows you to define the values for resilient modulus or the selected soil index and strength property.

Aggregate Gradation and other engineering properties

The aggregate gradation dialog box allows you to define the particle size distribution, Atterberg limits, specific gravity, water content, maximum dry density, saturated hydraulic conductivity and the SWCC parameters of non-stabilized materials. A description of the available inputs are summarized below.

• Sieve Size Table: This table allows you to define the percentage of non-stabilized material passing a variety of sieve sizes.
  • Sieve Opening Size (in, mm): This column lists the applicable sieve sizes.
  • Percent Passing: This column allows you to define the percentage of non-stabilized material passing a given sieve size. You are not required to define the percent passing for each sieve size. However, you are required to enter values for a minimum of 3 sieve sizes including No. 200 sieve.
  • Liquid Limit This control allows you to define the liquid limit of the non-stabilized material.
  • Plasticity Index: This control allows you to define the plasticity index for non-stabilized material.
  • Is Layer Compacted?: Enable this control to indicate that the layer is compacted. Typically non-stabilized materials used in the base and subbase layers are compacted in place during construction. Disable this control to indicate that the layer is not compacted.
  • Maximum dry unit weight (\(lb/ft^3\), \(kg/m^3\)): PMED internally computes the maximum dry unit weight of the non-stabilized material. This control allows you to override the internally computed value by enabling the check box. Click the check box to enable/disable this control.
  • Saturated hydraulic conductivity (ft/hr, m/hr): PMED internally computes the saturated hydraulic conductivity of the non-stabilized material. This control allows you to override the internally computed value by enabling the check box. Click the check box to enable/disable this control.
  • Specific gravity of solids: PMED internally computes the specific gravity of the non-stabilized material. This control allows you to override the internally computed value by enabling the check box. Click the check box to enable/disable this control.
  • Optimum gravimetric water content (%): PMED internally computes the moisture content of the non-stabilized material at which maximum dry density is achieved. This control allows you to override the internally computed value by enabling the check box. Click the check box to enable/disable this control.
  • User-defined Soil Water Characteristic Curve (SWCC): PMED internally computes the coefficients (af, bf, cf, and hr) of the soil water characteristic curve. This control allows you to override the internally computed value by enabling the check box. Click the check box to enable/disable this control.

Note:
PMED internally computes the values of the following properties based on the inputs for Gradation, Liquid Limit, Plasticity Index and Is Layer Compacted. The computed values are based on the defaults initially displayed on the input screen. However, if you choose to modify the default values, you are required to click outside the input screen for the program to update the internally computed values.

Note:
Input compatibility: It is essential that the values entered for water content, maximum dry unit weight are compatible. If the value water content entered represents optimium conditions, then the maximum dry unit weight at optimum conditions should also be entered.

Subgrade

Subgrade materials include AASHTO soil classes A-1 through A-3, as well as those commonly defined in practice as crushed stone, crushed gravel, river gravel, permeable aggregate, and cold recycled asphalt material (includes millings and in-place pulverized material).

Inputs required for subgrade materials include physical and engineering properties such as dry density, moisture content, hydraulic conductivity, specific gravity, soil-water characteristic curve (SWCC) parameters, classification properties, and the resilient modulus.

Interface

Figure 463: Subgrade

Methods to Populate Inputs

There are two methods for entering data: - Manual entry - Import from workspace library

Inputs

General Inputs

• Layer thickness (in, mm): This control allows you to define the thickness of the selected layer.
• Poisson’s ratio: This control allows you to define the Poisson’s ratio of the subgrade material. PMED provides a default value of 0.35.
• Coefficient of lateral earth pressure (k0): This control allows you to define the pressure that the unbound material exerts in the horizontal plane. PMED provides a default value of 0.5.

Figure 464: Subgrade Unbound

Resilient Modulus

Resilient Modulus (psi, MPa): This control allows you to define the level of inputs for resilient modulus of the unbound material. This control also allows you to define the resilient modulus or the other material properties that correlate with the resilient modulus. PMED displays the default value (Level 3) for the selected material class. Click on the Resilient Modulus control to modify the default value and/or input level.

• Input Level: This control allows you to define the level of inputs for the subgrade material. You can select one of the following options:
  • Level 1: PMED does not provide Level 1 inputs option for resilient modulus of subgrade materials.
  • Level 2: This option allows you to define the resilient modulus directly or using its correlations with soil index and strength properties. This level of input is considered as Level 2 in the AASHTO Manual of Practice.
  • Level 3: This option allows you to override the default resilient modulus value (Level 3) of the subgrade material.
• Analysis Types: These controls allow you to define how PMED accounts for seasonal variations (freezing, thawing and moisture) in the resilient modulus calculations. Select one of the following options: -Modify input values by temperature/moisture: This option allows you to define a single resilient modulus value. You can also input a single value of the selected soil index or strength property that is converted by PMED into a resilient modulus value. PMED incorporates the effects of seasonal variations on the single resilient modulus value you define. -Monthly representative values: This option allows you to define the resilient modulus throughout the year. You can input a single value of resilient modulus (or the selected soil index or strength property) for each month of a year. By selecting this option, you make PMED use the inputs you provide directly for seasonal variations without making internal adjustments. This option is available only for Level 2 inputs. -Annual representative values: This option allows you to define a fixed resilient modulus for an entire year. You can input a single value of resilient modulus (or the selected soil index or strength property) that is representative for an entire year. PMED does not incorporate the effects of seasonal variations on the single resilient modulus value you define.
• Correlation Methods to estimate Resilient Modulus: This control allows you to select how to estimate the resilient modulus using one of the following options:
  • Resilient modulus (psi, MPa)
  • California Bearing Ratio (CBR) (percent) R-value
  • Layer Coefficient-ai
  • Dynamic Cone Penetrometer (DCP) Penetration (in./blow, mm/blow)
  • Plasticity Index (PI) and Gradation (i.e., Percent Passing No. 200 (0.075mm) sieve)
• Input Entry Table: This control allows you to define the values for resilient modulus or the selected soil index and strength property.

Figure 465: Subgrade Modulus

Aggregate Gradation and other engineering properties

The aggregate gradation dialog box allows you to define the particle size distribution, Atterberg limits, specific gravity, water content, maximum dry density, saturated hydraulic conductivity and the SWCC parameters of subgrade materials. A description of the available inputs are summarized below.

• Sieve Size Table: This table allows you to define the percentage of subgrade material passing a variety of sieve sizes.
  • Sieve Opening Size (in, mm): This column lists the applicable sieve sizes.
  • Percent Passing: This column allows you to define the percentage of subgrade material passing a given sieve size. You are not required to define the percent passing for each sieve size. However, you are required to enter values for a minimum of 3 sieve sizes including No. 200 sieve.
  • Liquid Limit This control allows you to define the liquid limit of the subgrade material.
  • Plasticity Index: This control allows you to define the plasticity index for subgrade material.
  • Is Layer Compacted?: Enable this control to indicate that the layer is compacted. Typically subgrade materials used in the base and subbase layers are compacted in place during construction. Disable this control to indicate that the layer is not compacted.
  • Maximum dry unit weight (\(lb/ft^3\), \(kg/m^3\)): PMED internally computes the maximum dry unit weight of the subgrade material. This control allows you to override the internally computed value by enabling the check box. Click the check box to enable/disable this control.
  • Saturated hydraulic conductivity (ft/hr, m/hr): PMED internally computes the saturated hydraulic conductivity of the subgrade material. This control allows you to override the internally computed value by enabling the check box. Click the check box to enable/disable this control.
  • Specific gravity of solids: PMED internally computes the specific gravity of the subgrade material. This control allows you to override the internally computed value by enabling the check box. Click the check box to enable/disable this control.
  • Optimum gravimetric water content (%): PMED internally computes the moisture content of the subgrade material at which maximum dry density is achieved. This control allows you to override the internally computed value by enabling the check box. Click the check box to enable/disable this control.
  • User-defined Soil Water Characteristic Curve (SWCC): PMED internally computes the coefficients (af, bf, cf, and hr) of the soil water characteristic curve. This control allows you to override the internally computed value by enabling the check box. Click the check box to enable/disable this control.

Figure 466: Subgrade Sieve

Note:
PMED internally computes the values of the following properties based on the inputs for Gradation, Liquid Limit, Plasticity Index and Is Layer Compacted. The computed values are based on the defaults initially displayed on the input screen. However, if you choose to modify the default values, you are required to click outside the input screen for the program to update the internally computed values.

Note:
Input compatibility: It is essential that the values entered for water content, maximum dry unit weight are compatible. If the value water content entered represents optimium conditions, then the maximum dry unit weight at optimum conditions should also be entered.

Bedrock

A bedrock layer, if present under an alignment, could have a significant impact on the pavement’s mechanistic responses and therefore need to be fully accounted for in design. This is especially true if backcalculation of layer moduli is adopted in rehabilitation design to characterize pavement materials. While the precise measure of the stiffness is seldom, if ever, warranted, any bedrock layer must be incorporated into the analysis.

Interface

Figure 467: Bedrock

Methods to Populate Inputs

• Manual entry
• Import from workspace library

Inputs

Bedrock

• Layer thickness (in.): The program automatically defines the thickness of the bedrock layer as semi-infinite.
• Poisson’s ratio: This control allows you to define the Poisson’s ratio of the bedrock material. PMED provides a default value of 0.15 for solid, massive and continuous bedrock material and 0.30 for highly fractured, weathered bedrock material.
• Unit weight (pcf): This control allows you to define the weight per unit volume of the bedrock material. PMED uses a default value of 140 pcf.

Strength

• Elastic/resilient Modulus (psi): This control allows you to define the modulus of the bedrock layer. PMED provides a default value of 750,000 psi for solid, massive and continuous bedrock material and 500,000 psi for highly fractured, weathered bedrock material.

Figure 468: Bedrock Strength

Design and Layer Properties

New Flexible Design Properties

AC Layer Design Properties

To access this component, create a design with the top layer having an AC layer, and select “Design Properties”.

• AC Surface Shortwave Absorptivity: Defines the amount of available solar energy that is absorbed by the flexible pavement surface. PMED provides a default value of 0.85.

• Layer Interface: Opens a table that allows you to define the friction at the interface of adjacent layers in the pavement system.

  • Layer Name: Display name/ identifier you defined for the layer material type.
  • Layer Type: Layer material type associated with the layer name.
  • Interface Friction: Defines the friction of adjacent layers at their interface. Enter 0 for no friction (full slip condition), 1 for full friction (no slip), or between 0 and 1 for partial friction.

• Endurance limit: Define the threshold tensile strain value (endurance limit) in microstrain.

• Is endurance limit applied?: Determines whether or not you want to consider the endurance limit in the design analysis. Endurance limit is a threshold tensile strain value below which no load-related fatigue damage occurs in the AC layers. Select True to consider the endurance limit in the design analysis or False otherwise.

• Uses multi-layer rutting calibration: Enables or disables multi-layer rutting calibration factors in the design.

Figure 469: AC Layer Design Properties

Structural Response

PMED’s structural model analyzes pavement structure, accounts for discontinuities in that structure, and analyzes the effects of environment and traffic on that structure.

PMED produces the structure response outputs as intermediate files:

• Vertical compressive strain values are stored in the file “_VertStrain.txt”.

• Horizontal tensile strain values are stored in the file “_TensStrain.txt” The information contained in both files is as follows:

• Month

• SubMonth

• SubSeason

• Axle Number

• AC Modulus

• Load location

• Analysis location

• Strain (either vertical compression or horizontal tension) These files are located in the project folder where is the project file is stored.

PMED produces several intermediate files that contain a wide range of calculated output parameters. The contents of some of these files are described at http://www.me-design.com.

Calibration Factors

Calibration Factors for AC|Fractured JPCP include

AC Cracking-Bottom Up

• AC Cracking C1 Bottom: Asphalt concrete bottom-up cracking value for C1.
• AC Cracking C2 Bottom: The asphalt concrete bottom-up cracking value for C2 is provided for three different pavement thicknesses < 5in, 5in < thickness (hac) < 12in, and > 12in.
• AC Cracking C3 Bottom: Asphalt concrete bottom-up cracking value for C3.
• AC Cracking Bottom Standard Deviation: Dispersion from the average bottom-up cracking value for asphalt concrete.

Figure 470: AC Cracking Bottom-up

AC Cracking-Top Down

• AC Top-Down AC Cracking C1: Asphalt concrete top-down cracking value for C1.
• AC Top-Down AC Cracking C2: Asphalt concrete top-down cracking value for C2.
• AC Top-Down AC Cracking C3: Asphalt concrete top-down cracking value for C3.
• AC Top-Down AC Cracking kL1: Asphalt concrete top-down cracking value for kL1.
• AC Top-Down AC Cracking kL2: Asphalt concrete top-down cracking value for kL2.
• AC Top-Down AC Cracking kL3: Asphalt concrete top-down cracking value for kL3.
• AC Top-Down AC Cracking kL4: Asphalt concrete top-down cracking value for kL4.
• AC Top-Down AC Cracking kL5: Asphalt concrete top-down cracking value for kL5.
• AC Top-Down Cracking Standard Deviation: Dispersion from the average top-down cracking value for asphalt concrete.

Figure 471: AC Cracking Top-down

AC Fatigue

• AC Fatigue K1: Asphalt concrete repetitive-loading or fatigue damage value for K1.
• AC Fatigue K2: Asphalt concrete repetitive-loading or fatigue damage value for K2.
• AC Fatigue K3: Asphalt concrete repetitive-loading or fatigue damage value for K3.
• AC Fatigue BF1: The asphalt concrete repetitive-loading or fatigue damage value for BF1 is provided at three pavement thicknesses, < 5in, 5in < thickness (hac) < 12in, and > 12in.
• AC Fatigue BF2: Asphalt concrete repetitive-loading or fatigue damage value for BF2.
• AC Fatigue BF3: Asphalt concrete repetitive-loading or fatigue damage value for BF3.

Figure 472: AC Fatigue

AC Rutting

AC rutting calibration factors can be used in two ways:

Single-Layer AC Rutting Calibration You can assume the same set of calibration factors for all asphalt layers by setting Uses multi-layer rutting calibration under AC Layer Properties as “False”.

Figure 473: AC Layer Properties

AC rutting calibration factors include:

• AC Rutting BR1: Asphalt concrete longitudinal depression (wearing-away) value for BR1.
• AC Rutting BR2: Asphalt concrete longitudinal depression (wearing-away) value for BR2.
• AC Rutting BR3: Asphalt concrete longitudinal depression (wearing-away) value for BR3.
• AC Rutting K1: Asphalt concrete longitudinal depression (wearing-away) value for K1.
• AC Rutting K2: Asphalt concrete longitudinal depression (wearing-away) value for K2.
• AC Rutting K3: Asphalt concrete longitudinal depression (wearing-away) value for K3.
• AC Rutting Standard Deviation: Dispersion from the average longitudinal depression (wearing-away) value for asphalt concrete.

Multi-Layer AC Rutting Calibration You can assume different sets of calibration factors for each asphalt layer by setting Uses multi-layer rutting calibration under AC Layer Properties as “True”. You can add up to three asphalt layers for new flexible pavement; therefore, up to three sets of rutting calibration factors can be used.

Flexible IRI Calibration Factors

• IRI Flexible C1: Flexible pavement international roughness index (IRI) value for C1, which is the contribution from total rutting.
• IRI Flexible C2: Flexible pavement IRI value for C2, which is the contribution from fatigue cracking (both top-down and bottom-up).
• IRI Flexible C3: Flexible pavement IRI value for C3, which is the contribution from thermal cracking.
• IRI Flexible C4: Flexible pavement IRI value for C4, which is the contribution from site factor.
  

  Figure 474: IRI Flexible

IRI Flexible Over PCC

• IRI Flexible Over PCC C1: Flexible over PCC pavement IRI value for C1.
• IRI Flexible Over PCC C2: Flexible over PCC pavement IRI value for C2.
• IRI Flexible Over PCC C3: Flexible over PCC pavement IRI value for C3.
• IRI Flexible Over PCC C4: Flexible over PCC pavement IRI value for C4.
  

  Figure 475: IRI Flexible

Reflective Fatigue Cracking

• Reflective Fatigue Cracking AC C1: Reflective fatigue cracking C1
• Reflective Fatigue Cracking AC C2: Reflective fatigue cracking C2
• Reflective Fatigue Cracking AC C3: Reflective fatigue cracking C3
• Reflective Fatigue Cracking AC C4: Reflective fatigue cracking C4
• Reflective Fatigue Cracking AC C5: Reflective fatigue cracking C5
• Reflective Fatigue Cracking AC K1: Reflective fatigue cracking K1
• Reflective Fatigue Cracking AC K2: Reflective fatigue cracking K2
• Reflective Fatigue Cracking AC K3: Reflective fatigue cracking K3
• Reflective Fatigue Cracking AC Standard Deviation: Reflective fatigue cracking standard deviation equation
  

  Figure 476: Reflective Fatigue Cracking AC

Reflective Transverse Cracking

• Reflective Transverse Cracking AC C1: Reflective fatigue cracking C1
• Reflective Transverse Cracking AC C2: Reflective fatigue cracking C2
• Reflective Transverse Cracking AC C3: Reflective fatigue cracking C3
• Reflective Transverse Cracking AC C4: Reflective fatigue cracking C4
• Reflective Transverse Cracking AC C5: Reflective fatigue cracking C5
• Reflective Transverse Cracking AC K1: Reflective fatigue cracking K1
• Reflective Transverse Cracking AC K2: Reflective fatigue cracking K2
• Reflective Transverse Cracking AC K3: Reflective fatigue cracking K3
• Reflective Transverse Cracking AC Standard Deviation: Reflective fatigue cracking standard deviation equation
  

  Figure 477: Reflective Transverse Cracking AC

Subgrade Rutting

• Granular Base Rutting BS1: Subgrade longitudinal depression (wearing-away) value for BS1.
• Granular Base Rutting K1: Subgrade longitudinal depression (wearing-away) value for K1.
• Granular Base Rutting Standard Deviation: Dispersion from the average longitudinal depression (wearing-away) value for subgrade (Fine).
• Subgrade A-3 Rutting K1: Subgrade longitudinal depression (wearing-away) value for K1 and A-3 subgrade.
• Subgrade Coarse Grained Rutting K1: Subgrade (coarse) longitudinal depression (wearing-away) value for K1.
• Subgrade Fine Grained Rutting K1: Subgrade (fine) longitudinal depression (wearing-away) value for K1.
• Subgrade Rutting BS1: Granular base longitudinal depression (wearing-away) value for BS1.
• Subgrade Rutting Standard Deviation: Dispersion from the average longitudinal depression (wearing-away) value for granular base.
  

  Figure 478: Subgrade Rutting

PCC Cracking

• PCC Cracking C1: JPCP repetitive-loading or fatigue damage value for C1.
• PCC Cracking C2: JPCP repetitive-loading or fatigue damage value for C2.
• PCC Cracking C4: JPCP cracking value for C4.
• PCC Cracking C5: JPCP cracking value for C5.
• PCC Reliability Cracking Standard Deviation: Dispersion from the average cracking value for JPCP.

Figure 479: PCC Cracking

PCC Faulting

• PCC Faulting C1: Value for the elevation or depression of a C1 PCC slab in relation to an adjoining slab.
• PCC Faulting C2: Value for the elevation or depression of a C2 PCC slab in relation to an adjoining slab.
• PCC Faulting C3: Value for the elevation or depression of a C3 PCC slab in relation to an adjoining slab.
• PCC Faulting C4: Value for the elevation or depression of a C4 PCC slab in relation to an adjoining slab.
• PCC Faulting C5: Value for the elevation or depression of a C5 PCC slab in relation to an adjoining slab.
• PCC Faulting C6: Value for the elevation or depression of a C6 PCC slab in relation to an adjoining slab.
• PCC Faulting C7: Value for the elevation or depression of a C7 PCC slab in relation to an adjoining slab.
• PCC Faulting C8: Value for the elevation or depression of a C8 PCC slab in relation to an adjoining slab.
• PCC Reliability Faulting Standard Deviation: Dispersion from the average elevation/depression value of a PCC slab in relation to an adjoining slab.
  

  Figure 480: PCC IRI CRCP

PCC IRI-JPCP

• PCC IRI J1: JPCP IRI value for J1, which is the contribution from transverse cracking.
• PCC IRI J2: JPCP IRI value for J2, which is the contribution from joint spalling.
• PCC IRI J3: JPCP IR value for J3, which is the contribution from joint faulting.
• PCC IRI J4: JPCP IRI value for J4, which is the contribution from site factors.
• PCC IRI JPCP Std. Dev.: IRI standard deviation for J1 through J4.
  

  Figure 481: PCC IRI CRCP

PCC Punchout

• PCC CRCP C1: Broken area of a CRCP C1 slab bounded by closely spaced cracks (usually spaced less than 3 feet).
• PCC CRCP C2: Broken area of a CRCP C2 slab bounded by closely spaced cracks (usually spaced less than 3 feet).
• PCC CRCP C3: Broken area of a CRCP C3 slab bounded by closely spaced cracks (usually spaced less than 3 feet).
• PCC CRCP C4: Broken area of a CRCP C4 slab bounded by closely spaced cracks (usually spaced less than 3 feet).
• PCC CRCP C5: Broken area of a CRCP C5 slab bounded by closely spaced cracks (usually spaced less than 3 feet).
• PCC CRCP Crack: Broken area of a slab bounded by closely spaced cracks.
• PCC Reliability PO Standard Deviation: Dispersion from average of the broken area of a CRCP slab bounded by closely spaced cracks.
  

  Figure 482: PCC IRI CRCP