Warm-Mix Asphalt-Rubber Compactability Metrics: Optimization of Production and Compaction Temperatures

Description

Warm-Mix Asphalt-Rubber Compactability Metrics: Optimization of Production and Compaction Temperatures

Sri Gangadhar Mattaparthi

Doctoral Research Scholar, Department of Civil & Environmental Engineering, Indian Institute of Technology Tirupati, Andhra Pradesh 517 619, India, ce22d510@iittp.ac.in

Krishna Prapoorna Biligiri

Corresponding Author, Professor, Department of Civil & Environmental Engineering, Indian Institute of Technology Tirupati, Andhra Pradesh 517 619, India, Tel: +91-877-2503157; Fax: +91-877-2503004, bkp@iittp.ac.in

ABSTRACT. The major objective of this study was to evaluate the effectiveness of asphalt mix compactability metrics of warm-mix asphalt-rubber (WMAR) mixtures prepared with two warm-mix asphalt (WMA) additives: (i) an indigenously developed fly ash-based foaming additive using alkali-fusion hydrothermal method, which contained approximately 16% water content in the crystal structure (hereinafter referred to as FAZ), and (ii) a commercial foaming WMA additive, which was a fine granulated synthetic zeolite with 21% water content, followed by the determination of both production and compaction temperatures, chiefly to compare the reduction potential of WMA additives. The scope of the effort involved preparation of asphalt rubber (AR) binders, conduct of mix design to determine optimum asphalt content for mixture preparation, and determination of reduced mixing and compaction temperatures of WMAR mixtures through asphalt mix compactability test. The standard equiviscous approach adopted for estimating laboratory mixing and compaction temperatures significantly overestimated the respective temperatures for AR modified binders, highlighting the necessity to adopt mixture-based approaches for AR mixtures. The FAZ additive achieved a temperature reduction of 13 and 11 °C for AR15 and AR20 mixtures, respectively, whereas the commercial additive demonstrated about 23 and 17 °C reduction in the compaction temperatures of AR15 and AR20 mixtures. Nonetheless, FAZ still demonstrated perceptible temperature reduction capabilities, underscoring its potential as a sustainable WMAR additive aligned with the principles of circular economy through the valorization of fly ash wastes. Importantly, the temperature reductions observed using the asphalt mix compactability method aligned more closely with the supplier recommendations and reported field performance and hence can be adopted for assessing WMAR. However, future studies should explore the effect of different WMA additives, additive dosages and moisture retention on compactability characteristics to further refine the asphalt mix compactability method for wider adoption.

KEYWORDS: Warm-mix asphalt-rubber, Sustainable production and compaction temperatures, Compactability test, Sustainable pavement technology.