Study of the mechanical and microstructural properties of stone mastic asphalt containing Algerian date palm fibers: influence of the manufacturing process

摘要

This study investigated the use of date palm fibers (DPF) extracted from Algerian trees to improve the mechanical performance of wearing courses. For this purpose, fiber-based stone mastic asphalt (SMA) mixtures (0.3 wt% fibers) were prepared by wet and dry processes. Their flow properties, binder drainage, compactability, water sensitivity and rutting resistance were assessed and compared with those of a reference formula (without fibers). Moreover, the tridimensional fiber distribution inside the mixtures was determined using X-ray computed tomography. Marshall test results showed an increase in stability of approximately 23% after fiber addition for both wet and dry fabrication methods. Moreover, gyratory shear compaction experiments demonstrated that the incorporation of fibers resulted in a slight decrease in void content. Owing to the ability of the fibers to absorb bitumen, the wet process was found to be the most effective in reducing the draindown effect (approximately 50%). Moisture susceptibility tests highlighted that palm fibers imply an increase in water sensitivity at 40 degrees C, probably due to their hydrophilic nature. The introduction of fibers could improve rutting resistance of the mixtures at medium to long-term service life; in particular, using = 1 mm length fibers following the dry process provided the lowest permanent deformation. Macrostructure analyses revealed that palm fibers kept their shape, did not melt in asphalt mixtures and created a 3D networking mechanism without any agglomeration. Therefore, DPF can be promoted in SMA mixtures for the upper layers of asphalt pavements at hot climates.