Therefore, the difference in the depth of material that influences each detector and mathematical modeling allow the gauge to determine the density of only the top, newly placed lift (Troxler, 2002). The detector further from the source is more likely to detect gamma rays scattered by the material below the paved mat. Nuclear density gauges advertised as “thin lift” gauges account for this by using two Geiger-Mueller detectors, one closer to the source than the other. Nuclear gauge operation schematic.When operated in backscatter on relatively thin mats (less than 75 to 100 mm (3 to 4 inches)) gamma rays from the source will not only interact with electrons from the newly paved mat, they will also interact with electrons from material below the paved mat. Therefore, the detector count is proportional to pavement density.Ī calibration factor is used to relate gamma count to actual pavement density. The more dense the pavement, the higher the probability that a gamma ray will be redirected towards the detector. Gamma rays that are scattered towards the detector are counted. The source emits gamma rays, which then interact with electrons in the material and lose energy and/or are redirected (scattered). The retractable rod is lowered so that it is even with the detector but still within the instrument. A calibration factor is used to relate gamma count to actual pavement density. Therefore, the detector count is inversely proportional to pavement density. The more dense the pavement, the higher the probability of interaction and the lower the detector count. Gamma rays that lose sufficient energy or are scattered away from the detector are not counted. The retractable rod is lowered into the mat through a pre-drilled hole (this hole can be formed by pounding a steel rod with a similar diameter to that of the gauge’s retractable rod). Nuclear density gauges are typically operated in one of two modes, each of which uses a different correlation to determine pavement density (Figure 2): Pavement density is then correlated to the number of gamma rays received by the detector. #Manual densimetro troxler 3440 manuals#I found the manuals for my Teac A-3440 without any. The new TEAC A-3440 represents another advancement on an already widely accepted. Easy to operate, easy to power and easy to service. Humboldt’s HS-5001EZ Moisture/Density Gauge is just that - easy. A Geiger-Mueller detector (situated in the gauge opposite from the handle) counts gamma rays that reach it from the source. Gamma rays are emitted from the source and interact with electrons in the pavement through absorption, Compton scattering, and the photoelectric effect. Gauges usually contain a small gamma source (about 10 mCi) such as Cesium-137 on the end of a retractable rod. A nuclear density gauge measures in-place HMA density using gamma radiation.
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