LABORATORY INVESTIGATION ON PROPERTIES OF ASPHALT-UBBER BINDERS USED IN ASPHALTIC CONCRETE MIXTURES

Author: Khaled Khamaiseh

Supervisor: Dr. Taisir Khedaywi

Date of Defense: 1991

ABSTRACT

The objective of this study was four folds: First, to investigate the effect of rubber concentration on the physical properties of asphalt cement; Second, to study the effect of rubber particle size on the properties of asphalt cement; Third, to study the effect of an organic solvent on properties of asphalt-rubber mixtures; Fourth, to investigate the effect of rubber concentration on properties of asphalt-rubber concrete mixtures.

In order to study the effect of rubber material on the physical properties of asphalt cement. Asphalt-rubber blends were prepared by adding 5, 10, 15, and 20 percent of rubber, 0, 1, 1.5 and 2 percent of organic solvent and three sizes of particles to 80/100 grade asphalt cement. Asphalt-rubber blends were also used in preparing Marshall specimens to investigate the effect of rubber concentration on properties of asphalt-rubber concrete mixtures.

In both phases of the investigation, ASTM standard tests and MS-2 procedure were utilized in the laboratory preparing and testing. Graphical presentation and illustration were used where necessary. Test results and date analysis followed the experimental work.

In the first phase of investigation, three sizes of rubber particles (R1= No.16-No.20,R2=No.20-No.50,R3=No.50-No.500), four different rubber concentrations and four different solvent concentrations were utilized in preparing asphalt-rubber blends. The experimental work involved one grade of asphalt cement. Penetration, ductility, softening point, flash point and specific gravity of the binders were investigated. The results showed hat the penetration, ductility, flash point and specific gravity of the binders were inversely proportional with the increased amount of rubber in the binders for the three sizes of rubber particles being used. The softening point was directly proportional to the increase in percent of rubber and inversely proportional to the increase in percent of organic solvent. The data collected from the experimental work were used to study the effect of additives on the properties of asphalt cement by graphical method.

The second phase of the study was concentrated to study the effect of binders having different percents of rubber additives on general properties of asphalt concrete mixtures. Eleven binders having different percents and size of rubber were incorporated in asphalt-rubber concrete mixtures and their properties were also studied. The experimental work involved one type of aggregate.

The objective of this phase was to investigate the effect of rubber concentration and rubber particle size on the properties of asphaltic concrete mixtures. The data collected from the experiments was studied graphically.

The results show that asphalt-rubber concrete mixtures have lower stabilities than asphaltic concrete mixtures. Rubber particles size affects the properties of paving mixtures. Flow of asphalt-rubber concrete mixtures is higher than that of conventional asphalt concrete mixtures. The optimum binder content which satisfied the requirements of Ministry of Puplic Works and Housing (MPWH) is 6.0 percent accomplished when using 20 percent of No.20-No.50 rubber particles. This optimum binder content contains 4.8% asphalt and 1.2% rubber which means that there is a saving of 0.4% in asphalt knowing that optimum asphalt content is 5.2% (contrl mix).