Laboratory Performance Characteristics of Sulfur-Modified Warm-Mix Asphalt

Abstract

The objective of this study was to compare the laboratory mechanistic properties of sulfur-modified warm-mix asphalt (WMA) with conventional asphalt mixtures. Three mixtures, two hot-mix asphalt (HMA) and one WMA, were prepared. Mixture One used an unmodified asphalt binder classified as PG 64-22, Mixture Two used a styrene-butadiene-styrene elastomeric modified binder classified as PG 70-22, and Mixture Three was a WMA that incorporated a sulfur-based mix additive and a PG 64-22 binder. A suite of tests was performed to evaluate the rutting performance, moisture resistance, fatigue endurance, fracture resistance, and thermal cracking resistance of the three mixtures. Results of the experimental program showed that the rutting performance of sulfur-modified WMA was comparable or superior to conventional mixes prepared with polymer-modified and unmodified asphalt binders. Results of the modified Lottman test showed that the moisture resistance of the sulfur-modified mixture was comparable to conventional mixes. Results of the fracture tests showed that sulfur-modified WMA is more susceptible to cracking than conventional mixes, given its stiff characteristics. However, given these stiff properties, the higher modulus of sulfur-modified mixtures will reduce the magnitude of strain induced in the pavement. Thermal stress restrained specimen test results showed that the sulfur-modified WMA had greater fracture stress than the polymer-modified mixture. However, there was no statistical significance between the average fracture temperatures for the mixes tested.