Impact of Asphalt Additives on Rutting Resistance of Asphalt Concrete

Abstract

Rutting is considered as one of the major pavement distresses of flexible pavement in Iraq. The hot weather duration for five months with 40-50 ⁰C has negative impact on the rutting resistance of asphalt concrete pavement. It was felt that modification of asphalt cement may be a possible solution to overcome such issue. In this paper, two penetration grade asphalt cement (40-50 and 60-70) have been modified in the laboratory by digestion with five types of locally available additives (fly ash; crumb rubber; fumed silica, sulfur; and Phospho-gypsum). Asphalt concrete mixture usually used for wearing course construction in Iraq as per SCRB specifications of 19 mm nominal size was considered in this investigation. Specimens were prepared using both of conventional asphalt cement and modified asphalt cement. The prepared modified asphalt concrete mixtures were evaluated by using Marshall Tests, resilient modulus determination (MR) and resistance to permanent deformation under repeated loads test, and then compared with the conventional mixture. The asphalt concrete mixtures modified by 10% fly ash by weight of asphalt cement (60-70) exhibit high resistance to permanent deformation as compared with the control mixture, while the mixture modified by 3% sulfur by weight of asphalt cement (60-70) generally showed lower resistance to permanent deformation as compared to the other tested mixtures. On the other hand, 1% of Phospho- gypsum by weight of asphalt cement (40-50) exhibit an improvement in rutting resistance. Sulfur and fly ash showed negative impact on rutting resistance for the range of load repetition studied.