Fatigue of cold recycled cement-treated pavement layers : experimental and modeling study

Abstract

Fatigue is the main design criterion for cold recycled cement-treated mixtures (CRCTMs). However, the literature shows that the fatigue behavior of such mixtures is still not well known. For example, the effect of increasing reclaimed asphalt pavement (RAP) contents is yet a topic of discussion. This experimental and modeling study helps fill knowledge gaps on CRCTM fatigue behavior using long-term curing fatigue tests and three design methods currently being used in different countries. The objectives of this study were: (1) to characterize the mechanical and fatigue behavior of mixtures of RAP, aggregates and cement; (2) to evaluate the fatigue life of pavements with base and subbase layers of such mixtures using the novel Brazilian design method (MeDiNa); and (3) to compare the results with those obtained using the South African Pavement Engineering Manual (SAPEM) transfer functions and the American Association of State Highway and Transportation Officials AASHTOWare Pavement Mechanistic-Empirical Design (PMED) software. The mixtures were tested in the laboratory using flexural static and cyclic tests, and the required parameters to use the methods were obtained. Experimental results and modeling demonstrated a superior fatigue behavior of recycled layers with higher RAP contents. On the other side, layers with lower RAP contents abruptly lost stiffness in short periods, making thicker structures necessary. Therefore, using high RAP contents is not only a sustainable practice, but also a technical benefit. The equivalent single axle loads obtained using the SAPEM were higher than those obtained using MeDiNa, while the PMED ones were higher than both previous methods. Despite the inherent differences, this suggests that MeDiNa is more conservative. It also highlights the importance of calibration based on long-term pavement performance data.