Assessing Rheological Behavior of Modified Paving Asphalt Cement

The Asphalt cement is produced as by-product from oil industry in Iraq; the asphalt must practice further processing to control the percentage of its different ingredients so that it will be suitable for paving process. If such processing is not conducted, then another alternative of modifying the asphalt cement properties with additives could be implemented. The objective of this work is to prepare different types of modified Asphalt cement using locally available additives, and subjecting the prepared modified Asphalt cement to testing procedures usually adopted for Asphalt cement, and evaluates the suitability of modified asphalt cement for paving process requirements. An attempt was made to prepare the modified Asphalt cement for pavement construction in the laboratory by digesting each of the two penetration grade Asphalt cement (40-50 and 60-70)with sulfur, fly ash, fumed silica, crumb rubber and Phospho gypsum. Three different percentages of each of the above mentioned additives have been tried using continuous stirring and heating at 150- 160 o C for 30 minutes .The prepared modified Asphalt specimens were subjected to physical properties determination; such as (Cone penetration, Softening point, Resilience, Cold bond adhesion) to investigate its quality. Rheological properties such as Creep stiffness, Penetration index, Stiffness modulus and Penetration viscosity number were also investigated and compared. It was concluded that Sulfur additive provides the lowest creep stiffness at all of the loading periods and for both asphalt grades, while crumb rubber additive shows the highest creep stiffness. The softer asphalt 60-70 experience increases in the magnitude of m-60 by 84 percent when compared to harder asphalt of 40-50. Sulfur, Phospho gypsum, and fly ash increase the temperature susceptibility of both grades of asphalt cement, while Rubber and sulfur, improved the elastic properties of both grades of asphalt.