Tribology-Based Specifications for Assessing the Production Temperatures of Asphalt Binder

Abstract

The success of warm mix asphalt (WMA) technology and polymer-modified binders (PMB) depends on the accurate determination of the production temperatures. To date, no standard protocol has been developed to determine the production temperatures of the WMA technology. Recent studies have shown that the production temperature is related to the friction between the aggregate and asphalt binder, which can be explored using tribology. This study attempted to develop a tribology-based approach to evaluate the production temperature of WMA-modified binder and PMB. The ball-on-the-three-plate test was performed using different normal loads (1N, 3N, 5N, and 10N) and sliding speeds (0.05 m/s, 0.1 m/s, and 0.3 m/s). The test results were compared with the equi-viscous (EQ) method. Production temperatures obtained from the EQ method were inappropriate for WMA and PMB. Results of the tribology study showed that the normal load of 1N and 0.3 m/s was found suitable for evaluating the production temperatures. Adding WMA additives resulted in a lower coefficient of friction (CoF), whereas PMB showed higher CoF than viscosity grade binder (V8, which is used for WMA modification). The addition of WMA additive reduced the production temperatures of V8, and reduction was a function of the WMA additive type. Temperature ranges corresponding to the CoF of 0.26 ± 0.021 and 0.33 ± 0.023 were proposed for assessing the mixing and compaction temperatures, respectively.