RoadMat not only manages the materials database where a lot of information on existing pavement materials can be found (browse the RoadMat database), it also directly works on Research & Development (R&D) projects on road materials. An example of recent R&D activity of RoadMat is described in this short note, with a study on binder specifications. Specifications are necessary to make sure the right materials are being used in a construction project, with the objective to build long-lasting infrastructure. It is therefore a key aspect of constructing sustainable pavements, since only the use of proper specifications will guarantee that durability requirements can be met.

As explained in RoadMat Note 02 on binder specifications, the current Performance Grading system for asphalt binders in the USA, determines limiting temperatures for appropriate binder use. The low limiting temperature is based on rheological measurements made using the Bending Beam Rheometer (BBR) and the values of the creep modulus and/or its slope vs loading time (in a log scale), are being used. Each criterion, stiffness or slope, allows determining a low limiting temperature (respectively Tc(S) and Tc(m)). The highest value is retained for specification purposes (AASHTO 320 – see RoadMat Note 02). Now, it has been proposed adding a new criterion, called ΔTc (also called delta Tc), defined as the difference between these two limiting temperatures:

ΔTc = Tc(S) - Tc(m)

Its ability to better predict thermal cracking is the subject of intense discussions.