UnPavedRoad

Instructions

Understand and accept the disclaimer on the home page. You must click on the “Accept” button to accept the disclaimer before you can start the using the material design tool. You will need to accept the disclaimer each time you access the tool.
Have your field investigation datasheets and laboratory test results (grading analysis, plasticity index or preferably bar linear shrinkage, and California Bearing Ratio [CBR]) available for each layer that you sampled in the road as well as for any supplementary materials that you plan to use to increase the thickness or blend to improve material properties. These values should not be guessed or be based only on previous experience.
If you have used the tool before and remember the ID number that was issued to you when you clicked the “Save” button, enter it in the UserID box and then click the “Login” button. Your last design and supplementary materials library will be displayed. If you are a first time user, proceed to the “Project ID” entry.
Type in the road number or road name as well as a short project description. Note that only the characters visible on the screen will be seen on printouts.
Select the known number of layers in the existing road using measurements from your nvestigation (don’t guess!). The subgrade is considered as a layer. Depending on the number of layers that you choose, a data input table with the selected number of layers will be shown. The bottom layer will automatically be selected as the subgrade with an infinite depth.
For Layer #1 (i.e., the road surface), choose a layer description from the drop down menu. Choices are asphalt concrete, bituminous surface treatment (e.g., chip seal, Otta seal, microsurfacing), unpaved wearing course, aggregate base, and aggregate subbase.
Enter the layer thickness.
If you selected “asphalt concrete” as Layer #1, default values will be automatically assigned for the percent passing the 1 in., #4, #8, #40, and #200 sieves and for the plasticity index/bar linear shrinkage. These are typical values for milled asphalt concrete. Click the “Edit” button on the right side of the table if you prefer to enter actual or different values for this layer. If you selected a material type other than asphalt concrete, enter the percent passing the relevant sieves from your laboratory test results.
Repeat Steps 5 through 7 for the other layers. You will need to enter data in each of the columns for these layers. An error message will show in the box below the table if inappropriate data is entered (e.g., the percent passing the #8 sieve is greater than that passing the #4 sieve). Note that subgrade layer thickness is automatically set to infinite and cannot be edited.
Enter the thickness design of the road (i.e., total thickness of the layers above the subgrade). If you are uncertain of what the thickness design should be for the expected truck traffic and subgrade shear strength (California Bearing Ratio), click on the “Thickness Design” button to see the thickness design table from the FHWA Gravel Roads Construction and Maintenance Guide and select an appropriate thickness. Note that selecting a thinner than recommended thickness could result in rutting and/or impassable conditions during wet weather.

Enter your anticipated recycling depth up to a maximum of 12 in. Note that recycling depths deeper than 12 in. cannot be satisfactorily compacted, which will lead to a densification and likely rutting under traffic as well as a higher than desirable rate of gravel loss.
Click on the “Predict Performance” button. The expected performance of the new wearing course layer for different recycling depths up to that entered will be shown on the performance chart. If the plot meets your requirements (i.e., well within the “Good” area of the chart, and the minimum design thickness and CBR value for the combined material are satisfied), select this recycling depth and skip to Step 17 to print the results and save your design and Supplementary Materials Library. Note that the design will need to be validated by testing the blended material and checking that the results plot as predicted by the tool. Enter the results into the Validation Test Results Table and then click on the “Plot Validation” button to confirm that satisfactory performance of the blend is likely.
If the required performance cannot be achieved (i.e., the predicted performance plots in an area outside the “Good” area, or the design thickness or CBR is not satisfied) for the anticipated recycling depth, adjust the recycling depth or consider adding supplemental materials (which will need to be spread on top of the road prior to recycling).
To add supplemental materials, first add them to the Supplemental Materials Library. Click on the “Add Material” button. Enter a description (e.g., “RAP”, “Aggregate Base”, “Fines”, “Clay”, or the name of the source that the material will be obtained from) and the material properties from the laboratory test results. Click the “Add Material” button to add another material.
Enter the thickness and type of supplemental material. Note that in most instances, only one supplemental material will be required. Exceptions are when the primary supplemental material that will be used to increase thickness does not plot in the “Good” area of the chart after blending with the existing materials. If clay fines are required to increase the shrinkage product, the thickness will typically be low (e.g., less than 0.5 in.).
Repeat Steps 12 through 15 until a combination of the supplemental material and the recycling depth that provides satisfactory performance is determined. Remember that the properties of the calculated blend will need to be validated with laboratory tests and the results plotted on the chart to confirm that the blend will perform as predicted.
Click on the “Print” button to print the screen. Note that you will need to make appropriate settings on your printer setup page. A landscape format is recommended.
Click on the “Save” button at the top of the page to get a User ID that will allow you to recall and edit this design and your Supplemental Materials Library and to allow entering the validation test results after this testing has been completed.
If applicable, click on the “Chemical Selection Tool” button to short cut to this tool to select an appropriate chemical treatment for this wearing course blend. Use the validation test results for the material properties in the chemical selection tool.