The objective of this paper is to evaluate the use of the SSDetect in determining the specific gravities and water absorption of fine aggregates. A number of researchers have evaluated the SSDetect in determining the specific gravities of fine aggregate. American Association of State Highway and Transportation Officials (AASHTO) T-84 is the current standard test method for measuring the fine aggregate specific gravity and absorption used by most owner/agencies in the United States. In the test, a cone and tamp rod are used to find the saturated surface-dry (SSD) state of the fine aggregate after 15 hours of soaking in water. In addition to its time consuming nature, the procedure does not work well when identifying the SSD condition of angular and rough fine aggregate because they do not readily slump. A proposed test in lieu of AASHTO T-84 uses an automated device called the SSDetect, which utilizes a laser system to detect the SSD condition of the fine aggregate sample. The SSDetect relies on the principle of the transition of light rays from the laser being reflected to being refracted, a condition which depends on the moisture coating on the aggregate surface. A total of 17 different fine aggregate; 7 at different gradations, and the remaining 10 as received blends were tested by AASHTO T-84 and an SSDetect device. Natural sand, manufactured sand, limestone, gravel and steel slag were tested at different gradations whiles the as received fine aggregates were typical of those used for Hot Mix Asphalt (HMA) mixtures in Michigan. Results from this research study indicate that the SSDetect is reliable and accurate for determining the dry and SSD specific gravity, and can replace the existing AASHTO T-84 method.
Abstract