Dynamic Modulus of Recycled Pavement Mixtures

Pavement recycling techniques have been shown to be effective for rehabilitating pavements by reducing environmental impacts, construction costs, and time. For various reasons, many highway agencies have not widely embraced these processes despite the demonstrated advantages. One such reason is that the mechanical properties of these materials have not been widely studied, resulting in a lack of consensus on proper design values, which causes concern for highway agencies. This study sought to determine the dynamic modulus of field-produced and field-cured recycled pavement materials from 24 projects constructed in the United States and Canada. The dynamic modulus is one of the primary material parameters for mechanistic empirical pavement design and performance prediction. On the basis of a statistical test and observation of the constructed master curves, this study found that the three pavement recycling processes studied (cold central-plant recycling, cold in-place recycling, and full depth reclamation) had a similar range of dynamic modulus values. In addition, cold central-plant recycling and cold in-place recycling showed greater stiffness temperature dependency than that of full-depth reclamation, suggesting that the binder from the existing reclaimed asphalt pavement may play a role in their stiffness properties. The master curves also showed that the use of chemical additives generally increased the stiffness and reduced the temperature dependency of the recycled materials. The master curves showed that dynamic modulus values were similar when emulsified asphalt and foamed asphalt were used as the stabilizing and recycling agents.