The effects of lime and amines on the aging of asphalts and recycling agents

Abstract

This research was aimed at determining the effects of additives on the aging of asphalt cements and rejuvenated asphalt cements. This was accomplished by performing two experiments. The first experiment was to determine the effects of various amounts of quick lime (CaO) and hydrated lime (Ca(OH),) on SHRP AAA-I and SHRP AAF-1. The second experiment was to determine the effects of three different amines and various amounts of CaO on aged SHRP AAA-I and SHRP AAF-I rejuvenated with ABM-F2, YBF-F2, and AAF-F3. The experiments were designed and performed to study the oxidation rates, the hardening rates, the hardening susceptibilities, and if possible, the prediction of the critical times for pavement failure due to the hardening of the asphalt cements. The results from the first experiment showed that Ca(OH), was a better lime additive than CaO. CaO accelerated the oxidation rates although it improved the hardening susceptibilities. Ca(OH)2 improved the hardening susceptibilities as well but also slowed the oxidation rates. 4-(3-Phenylpropyl)-Pyridine and N-Phenyl-1-Naphthylamine from the second experiment increased the oxidation rates, dropped the initial viscosities, and decreased the critical times while the 2-Aminophenol improved the oxidation rates, had only a slight drop in initial viscosities, and greatly increased the critical times. Except for the health hazards, the 2-Aminophenol would be considered a good additive if it were determined to be cost effective. The second experiment also showed that CaO at the higher concentrations always improved the hardening susceptibilities of the rejuvenated asphalts and increased the critical times. Both positive and negative effects occurred at random to the oxidation rates of the rejuvenated asphalt cements.