Abstract
It is well known that the performance of hot mix asphalt (HMA) in service life is closely related to a proper aggregate gradation. A laboratory study was conducted to investigate the effects of nominal maximum aggregate size (NMAS) on the performance of stone matrix asphalt (SMA). The volumetric characteristics and performance properties obtained from wheel tracking tests, permeability test, beam bending test, contabro test are compared for SMA mixes with different NMAS. The results indicated that voids in mineral aggregate (VMA) and voids filled with asphalt (VFA) of SMA mixtures increased with a decrease of aggregate size in aggregate gradation. SMA30 had the lowest optimum asphalt content among all the mixtures. Increase of NMAS contributed to improvement of the rutting resistance of SMA mixtures. However, a decrease of NMAS showed better cracking and raveling resistance. Permeability rate of SMA was primarily affected by the air voids (AV) and break point sieve, but was also sensitive to aggregate gradation to some extent, with reduced NMAS corresponding to less permeability rate. Based on the test results, SMA5 and SMA13 are suggested to be used as a water-proof layer in bridge deck pavement, and SMA20 and SMA30 are suggested to be used as binder course in asphalt pavement, which needs to possess superior rutting resistance at high temperature.
Highlights
Stone matrix asphalt (SMA) has been used successfully in Europe for over 20 years
SMA is a type of hot mix asphalt (HMA) characterized by higher content of coarse aggregate and rich mastic, which is composed of relatively high contents of asphalt binder and mineral fillers, and small contents of fine aggregate and stabilized additives
The mix design results for four SMA mixtures are summarized in Table 6, in which optimum binder content, Air voids (AV), Voids in mineral aggregate (VMA), Voids filled with asphalt (VFA), Stability, flow value and retained stability are included
Summary
Stone matrix asphalt (SMA) has been used successfully in Europe for over 20 years. SMA was first used in Europe as a mixture to resist the wear of studded tires. Among all the elements in the composition of HMA, aggregate gradation is perhaps the most important one affecting the performance of asphalt mixture. The Bailey method has been promoted in recent years to select aggregate gradation in HMA and performed well in Illinois. For the HMA designed by Superpave mix design procedure, aggregate gradation is crucial to the volumetric properties, and an important determining factor in the performance of asphalt mixture. The aggregate gradation is known to affect the stiffness, stability, durability, permeability, workability, fatigue resistance, skid resistance and moisture sensitivity of asphalt mixture [8]. According to the results of an investigation by Ruth et al, a well-balanced, continuously graded mix provides the best rut resistance for Superpave mixtures [9]. The results are conducive to guide the design and application of SMA in actual projects
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