Abstract
The action of high repeated trucks load associated with dramatically elevated ambient temperatures leads to the most harmful distress in asphalt pavements occurred in Iraq known as rutting. Essentially, it is produced from the accumulation of irrecoverable strains, which mainly occurred in the asphalt layers. That visually demonstrated as a longitudinal depression in the wheel paths as well as small upheavals to the sides. Poly Phosphoric Acid (PPA) has been used as a means of producing modified asphalt binders and the interest to use it has increased in recent years. The PPA provides modified asphalt binder, which is relatively cheaply produced compared to polymer-modified asphalt. In this paper, PPA was used by three-percentages 1, 2 and 3 % of the weight of asphalt binder. Two asphalt binder grades were used in this study, 40-50 and 60 -70. The evaluation process based on conducting Marshall Test, Compressive strength test and the Wheel Tracking test. The optimum asphalt content was determined for eight asphalt mixture. The results of the index of retained strength of modified asphalt were slightly increased compared with conventional mixtures. The rut depth was determined by using wheel tracking device at different temperature (45 and 55 ºC) for each asphalt mixture under 10000 cycles and the results showed that modified asphalt with PPA produced mixtures with more rutting resistance than conventional asphalt mixture. Moreover, the effect of PPA on rutting resistance for asphalt grade 60-70 was higher than asphalt grade 40-50.
Highlights
Asphalt pavement is a durable surface material laid down on the ground surface meant to sustain vehicular traffic loading
Few of the contributions are summarized as follows: According to studies Al-Shaybani (2018) [3], Zhang et al (2018) [4] and Jafari and Babazadeh (2016) [5], Phosphoric Acid (PPA) improves the high temperature performance grade (PG) of asphalt binders with only minor effects on their properties at low temperatures, while Jafari et al (2017) use a PPA to modify a performance graded binder (PG 58-22) and the experimental program included use of three PPA contents (0.5, 1, and 1.5%) by weight of the binder and use of ants tripping limestone aggregates, and the results showed that PPA significantly improved rutting resistance of asphalt mixture [6]
The results show that stability was increased by 4.82, 14.45 and 21.65 % compared with conventional mixture AC (40-50) when using modified asphalt AC (40-50) with 1, 2 and 3% PPA respectively
Summary
Asphalt pavement is a durable surface material laid down on the ground surface meant to sustain vehicular traffic loading. Flexible pavements are immensely adopted in Iraq as it provides ease in construction, operating and maintenance, the summer in Iraq is very hot where temperature raised to more than 50 oC. It persists for a long time, nearly for five to six months. All roads situated in this area suffer from the phenomenon of rutting, and absence of control of the higher axial loads in preceding years. To improve the quality of the binder, it is essential to identify the proper parameter of the asphalt that controls the rutting in the flexible pavement [1]
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