Efficacy of Acid-Activated Bentonite-Derived Zeolite as a Foaming Warm-Mix Asphalt Additive: Synthesis, Dosage Optimization, and Performance Assessment in Asphalt Mixtures

The major objective of this research was to assess the efficacy of acid-activated zeolite synthesized in the form of a foaming warm-mix asphalt (WMA) additive using bentonite as the base raw material through dosage optimization and performance evaluation of the indigenously developed zeolite-based-WMA mixtures. The overall process essentially involved synthesizing of a zeolite with bentonite, hydrochloric acid, and sodium hydroxide as reagents, hereinafter called zeolite derived from acid-activated bentonite (Zeo-AB). The scope of the effort encompassed: pretreatment of bentonite to form acid-activated bentonite, synthesis of nine different zeolites from bentonite and acid-activated bentonite, thermogravimetric analysis on synthesized zeolites to select Zeo-AB, production of control and Zeo-AB-modified asphalt mixtures for dosage optimization of Zeo-AB additive and determination of reduction in the production temperature, and performance assessment of Zeo-AB-modified WMA mixtures. The acid-activated bentonite was found as a potential precursor for synthesizing foaming WMA zeolites in comparison with bentonite. Zeo-AB additive exhibited 21.48% water content and demonstrated that 0.8% addition of Zeo-AB additive by weight of the asphalt mix would aid in achieving a remarkable reduction of about 18°C during mixing and compaction of asphalt mixtures. The Zeo-AB-modified WMA mixtures displayed 25% better low-temperature thermal cracking resistance than the control asphalt mixtures but similar rutting resistance. Interestingly, the moisture susceptibility of Zeo-AB-modified WMA mixtures were higher than the control asphalt mixtures, indicating that future research must focus on understanding the physicochemical interaction of the Zeo-AB-WMA additive, asphalt binder, and aggregates in the complex asphalt mix matrix.