Using the NCAT Online Asphalt Mix Design Program

Individual using the NCAT Online Asphalt Mix Design Program

The Superpave mix design procedure has been adopted by transportation agencies across the United States for designing dense-graded asphalt mixtures. Many highway agencies have developed customized mix design spreadsheets to use in designing and approving asphalt mix designs.

With advancements in computer programing languages, NCAT engineers have developed the NCAT Testing Tool, a web-based Superpave mix design program. The tool is freely accessible on the Internet, which makes it easy to store data online. It can be updated with changes in AASHTO specifications, providing users immediate access to the latest version without downloading and re-installing software. Data saved by a user, such as stockpile data, is securely stored on the Auburn server so that only the single user ID can access it.

The program can be accessed at: https://cwstest.auburn.edu/ncat. Users without an Auburn University account will be able to register for a guest account on the main page.

After logging in, users can create a new mix design, share, remove, or copy an existing mix design, or download the user manual by clicking on the corresponding buttons. Users cannot share, remove, or copy a mix design until one has been created.

An asphalt mix design can be created using the following 10 steps.

Step 1: Setup. The user inputs basic mix design information, binder information, consensus and specific gravity test results, and the number of trial aggregate blends (at least one) to be evaluated.

Step 2: Aggregate Gradations and Consensus Properties. The user inputs the aggregate gradations and consensus properties.

Step 3: Gmm & Gmb Results for Trial Blend(s). The user inputs the maximum theoretical specific gravity (Gmm) and bulk specific gravity (Gmb) for each trial blend.

Step 4: Volumetric Results for Trial Blend(s). Once the required information is entered, the volumetric properties for trial blends are calculated and the optimum binder contents are estimated. The user can review the volumetric properties of each trial aggregate blend and select the blend that best meets the mix design requirements. The user also selects an estimated optimum binder content for further evaluation.

Step 5: Selected Design Aggregate Structure. The design aggregate gradation and its combined aggregate properties are summarized.

Step 6: Gmm & Gmb Results for Three Asphalt Contents. The user enters Gmm and Gmb test results and sample heights at Nini and Ndes for three trial asphalt contents (optimum and optimum ± 0.5%).

Step 7: Volumetric Results for Three Asphalt Contents. The volumetric properties are automatically calculated and plotted for the three trial asphalt contents. The detailed volumetric properties are also included on this page. Based on the volumetric results, the user can select the optimum asphalt content and determine other volumetric properties for the design aggregate blend.

Step 8: Gmm & Gmb Results at Optimum Asphalt Content Compacted to Nmax (Optional). If testing is also conducted on samples mixed at the optimum asphalt content and compacted to the Nmax, the Gmm and Gmb test results as well as specimen heights at Nini, Ndes, and Nmax can be entered on this page. This step is not required in some state agencies’ specifications.

Step 9: Moisture Susceptibility (TSR) Inputs. The user enters tensile strength ratio (TSR) test data, which are then used to calculate the indirect tensile strengths and tensile strength ratio for reporting moisture susceptibility.

Step 10: Job Mix Formula Report. All of the mix design information and test results are summarized on this page. This includes general information, design gradation, optimum binder content, and other volumetric properties for the final mix design.