Engineering properties and air void characteristics of cold recycled mixtures with different compaction methods

Abstract

Cold recycled mixtures (CRM) offer advantages in terms of resource conservation and reduced CO2 emissions. This paper utilizes the vertical vibration testing method (VVTM), Marshall compaction (MC), Superpave Gyratory Compactor (SGC), and field core samples to analyze the effects of different compaction methods on the engineering properties of CRM. The study begins by discussing the volumetric and mechanical parameters of CRM with different compaction methods, followed by an analysis of fatigue performance. Additionally, CT scanning technology is used to study the effect of different compaction methods on the void characteristics of CRM. The results demonstrate that VVTM specimens offer better mechanical properties compared to MC and SGC specimens. Furthermore, the RT (splitting tensile strength), MS (dry-wet tensile strength ratio), and TSR (freeze-thaw splitting strength ratio) of VVTM specimens exhibit the highest correlation with field core samples, reaching 97%, 97%, and 95%, respectively. The VVTM specimens also exhibit the biggest fatigue, which is similar to that of the field core sample. The Weibull distribution model is utilized to predict the fatigue life of CRM with different compaction methods, with the fatigue equation indicating that VVTM specimens have better fatigue performance. In addition, the number of voids, diameter of voids, and fractal dimension of VVTM specimens along the longitudinal direction are closer to those of field cores. The fractal dimension of CRM specimens with different compaction methods is between 1.2 and 1.4, indicating that the complex shape of voids may alter stress concentration and impact the performance of CRM.