Effect of antistripping additives on environmental damage of bituminous mixtures

The main objective of this study was to investigate the effect of environmental damage (stripping) on the hot mix asphalt (HMA) creep behavior. To achieve this objective, 24 different HMA combinations using different mix parameters were evaluated for their resistance to static creep deformations. The mix parameters include: two types of asphalt cement, three types of aggregate gradation, and two types of antistripping additives (limestone dust and calcium stearate hydroxide). Marshall specimens were prepared at optimum asphalt contents and tested for static creep. Part of the prepared specimens were exposed to freezing–thawing conditioning according to AASHTO T283.The findings of this study indicated that conditioning of HMA specimens has a significant effect on the increase of creep deformation. This is especially true for open graded aggregate gradation mixes. For unconditioned mixes and conditioned mixes, prepared using mid and upper limits of ASTM specification for dense graded aggregate, the creep deformation of mixes prepared using 80/100 asphalt was less than that for mixes prepared using 60/70 asphalt. The opposite trend was noticed for conditioned specimens prepared using open graded aggregate gradation. Antistripping additives showed significant effect on reducing stripping and creep behavior. Mixes which used calcium stearate hydroxide additive showed less stripping and creep deformation than those which contained limestone dust additive.