Performance evaluation and adaptability optimization of hot mix asphalt reinforced by mixed lengths basalt fibers

Abstract Fiber length could well affect the properties of hot mix asphalt (HMA) modified by basalt fiber (BF). To investigate the effect of mixed lengths BF on the performance of HMA, and to explore the adaptability of the optimum mixed lengths to the morphological parameters of mixture, BF with different lengths (3, 6, 9, 12 and 15 mm) were selected, and HMA samples were fabricated with mixed lengths BF. The macro-performance tests including indirect tensile asphalt crack (IDEAL-CT) test, four-point bending fatigue test, wheel tracking test, uniaxial penetration test, freeze–thaw splitting test and low temperature bending beam test were employed, besides morphological parameters of the mortar in HMA samples were quantitatively analyzed by Imaging System. The results showed that compared with single length, BF with mixed lengths can further improve the comprehensive performance of HMA to a great extent, especially for the crack resistance related ones. Specifically, when the mass ratio of mixed basalt fiber lengths of 3 mm:6 mm:9 mm = 1:1:1, Superpave-13 can obtain the best enhancement, similarly, mixed lengths of 6 mm:9 mm:12 mm = 1:2:2 and 9 mm:12 mm:15 mm = 2:2:1 are recommended for Superpave-20 and Superpave-25, respectively, furthermore, the result of optimum mixed lengths is strongly in connection with the size of the axis (major) distribution of asphalt mortar, which depends on the skeleton structure of gradation. These findings provide a significant guidance for the better application of basalt fibers for road engineering.