Evaluation of Dynamic Shear Rheometer Tests for Emulsions.

摘要

DSR-based rheological tests of 20 different asphalt emulsion residues were performed and relationships with elastic recovery (AASHTOT301) and force ductility (AASHTO T300) were investigated. In strain sweep test from 2% to 52%, it was observed that emulsions prepared of hard pen base asphalt have relatively lower strain tolerances. Using frequency sweep data, complex modulus master curves were constructed at 25°C to understand overall rheological behavior. Temperature sweep of phase angle from 52°C to 94°C showed that a maximum phase angle in the range of 75° to 85° may be used as a criterion for polymer identification. MSCR (AASHTO TP70) at 58°Chas been recommended to replace the elastic recovery test (AASHTO T301). At 0.1kPa creep stress, a minimum percent recovery of 25and at 3.2kPa, a minimum percent recovery of 9 are recommended to identify the presence of polymer replacing elastic recovery test(AASHTO T301). Also, percent recovery of MSCR and phase angle can be used to replace force ductility requirements (AASHTOT300). It is recommended that at 58°C, a maximum phase angle of 81° and a minimum MSCR percent recovery (at 0.1kPacreep stress) of 30 can be specified to replace the force ductility test (AASHTO T300). These criteria are applicable foremulsion residues prepared according to the low temperature evaporative method specified in ASTM D7497. However, a comparative study among ASTM D7497 (24 hr at 25°C and 24 hr at 60°C), ASTM D6934 (3 hr at 163°C), AASHTO TP 72Method B (6 hr at 60°C), vacuum dry method (6 hr at 60°C, a method developed in this study) and field curing have been performed in order to develop a low temperature low duration recovery method. It was observed that the MSCR test on residue prepared with the vacuum dried method can be used for polymer identification replacing elastic recovery and force ductility tests. Finally, the current specification viscosity range for low and high viscous emulsions using the saybolt furol viscometer to ensure quality control and quality assurance can also be replaced by the rotational viscometer. The ranges recommended are 220 - 730 cP and 5 – 90 cP (gives 98% probability) at 50 rpm and 30°C for high and low viscous emulsions, respectively.