Laboratory Secondary Forming Temperature of Cold Recycled Mixture by Simulating Field Secondary Thermal Compaction

Abstract:

In order to make the design of cold recycled mixture in the laboratory truly reflect the actual working conditions in the field， this paper measured the process of temperature variation in the cold recycled layer during the construction of the hot-mix asphalt（HMA） mixture above the cold recycled layer. Based on the measured temperature， the effect of the cold recycled layer thickness， the overlying hot-mix layer thickness， and construction seasons were analyzed. The temperature prediction equations in the cold recycled layer were established. Simultaneously， the volumetric parameters and mechanical strength of the core samples after the secondary thermal compaction of the cold recycled layer at different construction temperatures were tested. The results show that during the paving process of the HMA， the temperature change in the cold recycled layer is greatly affected by the construction environment. The void ratio， flexural tensile strength， shear strength， and fracture work of cold recycled mixture are significantly affected by the construction temperature and laboratory secondary forming temperature. Compared with 0 ℃， when the construction temperature is about 30 ℃， the void ratio is reduced by about 25%， while the flexural tensile strength， shear strength， and fracture work are increased by at least 45%， 66%， and 77% respectively. Compared with 40 ℃， when the laboratory secondary compaction temperature is 80 ℃， the void ratio decreases by about 20%， while the flexural tensile strength， shear strength， and fracture work increase by at least 42%， 35%， and 80% respectively. The influence of secondary forming temperature should be considered in the design of cold recycled mixture to simulate the effect of the cold recycled layer on the performance due to the change of internal temperature.