Zeolite-Like Warm-Mix Asphalt Additive: Dosage Optimization Based on Asphalt Binder Characterization

The major objective of this research was to augment the temperature reduction characteristics of the recently developed sodium aluminate tetraethyl ammonium hydroxide montmorillonite (STEAM) warm-mix asphalt (WMA) additive by optimizing 8 dosages of 20 STEAM variants mixed with one viscosity graded-30 base asphalt binder. As the first step in the optimization process, a series of molar combinations of sodium aluminate and tetraethyl ammonium hydroxide were blended with constant concentrations of weights of montmorillonite (MMT) and water. The Fourier transform infrared (FTIR) spectroscopy test was performed on all the 20 STEAM variants to derive the hydroxyl functional groups and understand if they have potential in reducing the mixing and compaction temperatures of the STEAM-modified asphalt binder. The FTIR results indeed indicated that hydroxyl bonds increased with increasing MMT content, as a consequence of MMT releasing itself when mixed with the base asphalt binder. Next, the STEAM additives were mixed with the base binder at 8 dosages with 2 molar ratios covering 20 STEAM-modified asphalt binders on which penetration, softening point, and rotational viscosity tests were performed mainly to establish the ASTM A(i)-VTSi relationships. Depending on the combination of molar ratio and dosages, the STEAM-modified asphalt binders demonstrated a decrease of about 3 degrees C-8 degrees C of mixing and compaction temperatures. Furthermore, the STEAM additive that exhibited highest reduction in mixing temperature was blended with dense-graded aggregate gradation to produce a STEAM-modified asphalt mix, which reduced the production temperature by 10 degrees C based on the equivalent mixture performance criterion while also demonstrating stiffness performance similar to that of a control mix. Overall, the optimized indigenous STEAM WMA additives proved to be water-containing, zeolite-like products that have immense capacity in minimizing the working temperatures, albeit further studies should focus on tapping the full potentiality of several STEAM combinations to render the products as globally acceptable "green" paving materials.