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

36CHAPTER 3 EQUIPMENT3.1 INTRODUCTIONThis research required the use of various equipment and apparatus to develop the required mixdesigns and rut test results. All of the equipment that required calibration was calibrated beforetheir use. Proper use of all equipment was also learned and practiced. The following sectionspresent brief descriptions of the equipment used and an overview of the procedures for bothcalibration and use of this equipment. Equipment described includes the Marshall CompactionHammer, Marshall Testing Machine, Superpave Gyratory Compactor and the Asphalt PavementAnalyzer.3.2 MARSHALL COMPACTION HAMMERPine Instrument Company of Grove City, PA City manufactured the Marshall compactionhammer used for this research. It is comprised of a specimen mold, compaction hammer, liftingapparatus, and counter. For asphalt pavement mixtures containing aggregate up to 1-inchmaximum size, a mold with a diameter of 4 inch is used. Since the mixes for this research arewearing type mixtures, containing a nominal maximum aggregate size of 3/8 in., the 4 in. moldwas used. The compaction hammer is comprised of a hammer with a flat, circular tampingsurface with a diameter of 3 7/8 in. and has a sliding weight of 10 0.02 lb. The free fall drop ofthe hammer was 18 0.06 in. The lifting apparatus is basically a rotating chain that repeatedlylifts the compaction hammer to the proper height and releases to allow the hammer to free-fallto the sample. The counter automatically stops the compaction once a set number of drops isreached. For Marshall mix design this set number of blows varies with the traffic level of thepavement being designed. This research used 50 blows per side for the medium traffic mix and75 blows per side for the heavy traffic mix as per WVDOH specifications. The AASHTOprocedure for calibrating the hammer was not used, as it is not practiced in West Virginia. Moredetailed information on the Marshall Compaction Hammer can be found in AASHTO T 245-97.3.3 MARSHALL TESTING MACHINEThe Marshall Testing Machine is a device used to determine the resistance to plastic flow andstability of Marshall specimens compacted with the Marshall Compaction Hammer (AASHTO T245-97). The testing machine used for this research was a Pine Instruments AF850T MarshallTesting Machine. This apparatus is made up of a compression device, load head, load cell, x-yplotter and water bath.To properly test a Marshall sample for flow and stability the samples must first be conditioned ina water bath at 140 2 F for 30 to 40 minutes. This water bath has a resting surface for thesamples that is 2 in. above the bottom of the bath. After the samples have soaked for theproper time they are dried and placed into the load head that resembles a cradle-like surface.The load head is comprised of two pieces so the sample can be loaded onto the bottom half ofthe load head and then the top half can be put on top to enclose the sample. The load head and