Comparison of 9.5 mm SuperPave and Marshall Wearing I Mixes in ...

11mix design was developed to design asphalt pavement mixtures consisting of aggregates with anominal maximum size less than 19mm. Because of this, a relatively small mold was selectedfor the compaction of test samples. This mold was 102mm in diameter and accommodated amaximum aggregate size of 25mm. The weight of sample compacted in this mold isapproximately 1200g.Prior to compaction, the aggregates, asphalt cement and all equipment, which come in contactwith the mix are heated to the mixing temperature. The asphalt cement supplier generallyidentifies the mixing temperature based on the viscosity temperature characteristics of thebinder.When the mix is at the correct temperature, it is placed in the mold and the compaction begins.Both the mold, including top and bottom plates, and the head of the drop hammer are heatedto the compaction temperature prior to compacting the samples. Once compacted, the sampleis allowed to cool and extracted from the mold. The sample is then cooled to room temperatureprior to obtaining the weights required for determining the bulk specific gravity.Bulk specific gravity is measured in accordance with AASHTO T 166-00 as soon as the compactedspecimens have cooled to room temperature. Method A of the above standard is describedsince it is the procedure used in this research. First, the sample weight is measured andrecorded. The sample is then submerged in water at 77 F for 4 1 minutes and that weight isrecorded. The sample was then removed from the water, quickly blotted dry with a damp toweland weighed as the saturated dry condition. Bulk specific gravity is computed as:AG mb[2.3]B CWhere,G mb = bulk specific gravityA = mass of sample in air (g)B = mass of surface-dry specimen in air (g)C = mass of sample in water (g).Once the bulk specific gravity of the specimen is determined, stability and flow tests areconducted in accordance with AASHTO T 245-97. The sample is brought to a temperature of140 F by immersion in a water bath for 30 to 40 minutes. It is then removed from the bath,blotted dry and placed in the loading head of the Marshall testing machine. Load is then appliedto the test specimen at a rate of 2 in/min. The load and deformation data are recorded on an x–y plotter.