DEVELOPMENT OF AN OPTIMIZED PERFORMANCE-GRADED (PG) ASPHALT BINDER FOR UZBEKISTAN'S ROAD-CLIMATIC CONDITIONS AND TRAFFIC LOADS: RHEOLOGICAL CHARACTERIZATION AND HYBRID POLYMER MODIFICATION

This study characterized a BND 50/70 paving-grade asphalt binder used in Uzbekistan and evaluated four polymer-modification strategies designed to achieve a PG 76-28 performance grade. The testing program included rotational viscosity, flash point, dynamic shear rheometer testing of unaged and rolling thin-film oven-aged binders, multiple stress creep recovery (MSCR), pressure aging vessel aging, and bending beam rheometer (BBR) testing. The modifiers were TITAN 7686 plastomer, LG501S styrene-butadiene-styrene elastomer, their hybrid combination, and a hybrid formulation containing 1.0% Reclamite® plasticizer. For base-binder measurements with available duplicates, means, sample standard deviations, and coefficients of variation were calculated. The base binder had a mean viscosity of 0.625 ± 0.038 Pa·s at 135 °C and a mean flash point of 270.0 ± 8.49 °C. Polymer modification increased the reported critical high temperature to 77.62 °C with TITAN 7686, 83.30 °C with 3.0% LG501S, 83.10 °C with the LG501S/TITAN hybrid, and 79.30 °C with the LG501S/TITAN/Reclamite® hybrid. The optimized formulation had an S(60) value of 170 MPa and an m-value of 0.305 at −18 °C, with a reported critical low temperature of approximately −29.1 °C. It was therefore classified as PG 76-28. Because replicate-level observations were unavailable for every modified formulation, inferential statistics were not applied. The results support hybrid elastomeric-plastomeric modification with controlled plasticization, while additional replicate MSCR and mixture-level validation remain necessary before field implementation.

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