Characterization of asphalt mixtures produced with short Pulp Aramid fiber (PAF)

Use of additives and modifiers as an effective alternative to mitigate premature cracking of flexible pavements has been gaining popularity during the past three decades. Several studies have discussed the advantages and disadvantages of using various types of fibers in pavement industry. The objective of this study is to evaluate the impact of using Pulp Aramid Fiber (PAF) in Hot Mix Asphalt (HMA) in terms of mix design and performance. Aramid fibers or aromatic polyamide fibers were the first type of organic fibers found to have sufficient tensile strength and modulus to be used in advanced composites. Although studying the effect of additives on performance of HMA mixes has been the focus of several studies, the extent of work on the use of PAF in HMA mixes using a comprehensive methodology has been limited. A control mix and a PAF modified HMA mix were designed and evaluated with respect to their rutting resistance, fatigue cracking resistance, and low temperature cracking performance. The results indicate that mixes with PAF led to higher demand for bitumen content to achieve the same air void level as compared to the control mix. However, it was concluded that this additional binder content along with the presence of PAF resulted in an enhanced performance, especially with respect to fatigue cracking as well as improved ductility at cold temperatures. In spite of the additional binder content, the PAF modified mix exhibited satisfactory permanent deformation performance at high temperatures while considerably improving the fatigue and low temperature behavior of the mix. The results also indicate that PAF can delay cracking failure in long-term life of asphalt concrete mixes under repeated loading.