بهبود عملکرد مخلوط آسفالت با ماکرو فیبر شیشه ای Improvement of asphalt mixture performance with glass macro-fibers

1. Introduction Fibers have been used for centuries to reinforce brittle materials and influence the cracking process by increasing toughness, tensile strength and durability. As an example, Fiber Reinforced Concrete (FRC) has been developed. Although asphalt concrete has a viscous elastic behavior at medium to high pavement temperatures, it performs as a brittle material at low temperatures. In the pavements field, fibers have not been extensively used to reinforce asphalt concretes. Cellulose fibers with a large specific area are commonly used in mixtures like stone mastic asphalt (SMA) or porous asphalts to add a major percentage of asphalt that these mixtures require without binder drain down during the mixing and placement process [1–3]. Mahrez et al. [4] studied an SMA with glass microfibers finding improvements in dynamic modulus and fatigue behavior; they also found improvements in the rutting behavior of the mixture. The benefits of fibers in rutting improvement can be due to increases in the consistency of the mastic and lock mechanism between aggregates [5]. An interesting phenomenon was observed by Kutey et al. [6] while performing the Accelerated Loading Facility test. Asphalt concretes with polyester microfibers showed the presence of microcracks, but they do not progress or increase to a level of alligator crack patterns. In this case, as well as in FRC, fibers act like a bridge transferring stresses and limiting the growth of cracks. Many investigations have reported improvements in behavior of Fiber Reinforced Asphalt Concretes (FRAC) [7–17]. However, all mentioned works refer to short fibers (length <25 mm). To the author’s knowledge, no studies incorporating macrofibers (length >35 mm) are available. Additionally, it was observed that no design method exists for this type of FRAC mixture. The fibers are normally used in mortars and Portland cement concretes to control cracking and obtain residual load capacity in cracked states. The action mechanism and improvements of macrofibers in the field of asphalt concrete mixtures are still very much unknown. This work analyses the effects of fiber incorporation on the performance of asphalt mixtures regarding fracture response at low temperatures and rutting at high pavement service temperatures. Results from asphalt mixtures incorporating both micro and macro glass fibers are compared with those obtained on control asphalt concretes without fibers.