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• ® FP"gMtNTAAN JUIV 201.r; <br /> 3WI C r Aft Rome.O.Bw 1teNia wwa T WngW Internatl W- Ltd. <br /> A$k or �W ComwaMla Road,P.O.Boot 12067,Reaaarah TrlrpN Park NC 27T06-USA <br /> The Leader in Constriction Testing Equipment <br /> TNaphorw 1.610.64i6661 T*Ww 1.6/6.6MOM YWO:keda b&eem <br /> Application Brief <br /> TROXLER MODEL 3"0 <br /> RoadreaderTM <br /> Nuclear Moisture Density Gauge <br /> September 2007 <br /> Introduction <br /> The Troxler Model 3440 RoadreaderTM'nuclear moisture/density gauge offers two test modes for <br /> measuring the density of soil, aggregate,concrete and asphalt materials. The direct <br /> transmission mode allows the source to be lowered below the surface in order to test a larger <br /> area of material and improve gauge precision. In backscatter mode the source is positioned <br /> near the surface of the test material and the top four inches of material are penetrated by <br /> gamma rays. Moisture content of the material is also tested in a manor similar to the backscatter <br /> mode. The Model 3440 provides many special functions and features in order to achieve the <br /> highest level of operator convenience. This gauge prompts the user through the steps of <br /> accessing and enabling all functions.This application brief will describe the operation, <br /> application and features of the Model 3440 RoadreaderTM'Surface Moisture/Density Gauge. <br /> Measurement Technology <br /> Surface nuclear gauges use the interaction of gamma radiation with matter to measure density <br /> through direct transmission or backscatter. In the direct transmission position the source rod <br /> extends through the base of the gauge into a preddW hole up to 30 cm(12 in.)deep in the <br /> material being tested. The gamma rays are transmitted from the density source,through the <br /> test material and are counted by detectors located within the gauge. The average density <br /> between the source and detectors is then determined. The backscatter mode is a rapid and <br /> nondestructive means of testing materials that are approximately 10 cm (4 in.) in depth. The <br /> gamma source and the detectors remain inside the gauge,which rests on the surface of the test <br /> material. Gamma rays from the density source enter the test material. Those that are scattered <br /> back toward the detectors are counted,determining the density count for the material. This <br /> means of testing is usually used on asphalt and concrete.The photons counted is in direct <br /> relation to the density of the material;the higher the counts the lower the density,and the lower <br /> the counts the higher the density. Calibration constants, acquired in the factory during <br /> calibration on blocks of known density or moisture content,are used by the gauge to convert the <br /> counts obtained in the field test to a density or moisture measurement <br /> Moisture content is also measured in a nondestructive test mode. Moisture is determined <br /> through the detection of thermalized neutrons("Fast"neutrons which have been sowed by the <br /> hydrogen present in the material, normally in the form of water). As the moisture level of the test <br /> material increases, neutrons are thermalized at a greater rate so the moisture count increases. <br /> AB3440-0 N2 1 <br /> 12 <br />