Development of Routine Resilient Modulus Testing: New Devices and Procedures

PROBLEM STATEMENT When designing and evaluating asphalt pavements, engineers must have an understanding of how the pavement materials will react to the stresses and strains of vehicle loads at varying temperatures. When a load is applied to asphalt concrete at a certain temperature, to what degree will the pavement "bounce back" to its original height? Pavement designers predict this spring-like behavior by obtaining the resilient modulus of the material a single number that describes the stress-strain relationship. If a pavement has a high resilient modulus, then we can indirectly assume it will have better performance and less permanent deformation. The 1986 AASHTO (American Association of State Highway Transportation Officials) Guide for Design of Pavement Structures incorporates resilient modulus testing of pavements into the design and evaluation procedure, and the Asphalt Aggregate Mixture Analysis System (AAMAS, NCHRP Report 338) uses resilient modulus to measure engineering properties (fatigue and thermal cracking, moisture damage, and rutting predictions) of mixtures and then judge the potential of these mixtures to function in pavement layers. The Texas Department of Transportation (TxDOT) has not routinely performed resilient modulus tests in the past. Additionally, the most common existing laboratory and nondestructive field tests (NDTs) for Resilient Modulus have shown limitations such as instrumentation problems, deviation of the actual procedure from the theory upon which it is based, and wave propagation anomalies.