FACTORS AFFECTING THE DRY DENSITY OF MATERIALS USING NUCLEAR DENSITY GAUGES IN HIGHWAY CONSTRUCTION

Abstract

This research studied the factors affecting the dry density measurement read from nuclear density gauge in highway construction work. The pavement structure of this study included earth embankment, soil aggregate subbase, and crushed rock soil aggregate type base. This study also compared backscatter and direct transmission methods with sand replacement method. Both the backscatter and the direct transmission methods were read at 15 seconds, 1 minute, and 4 minutes from the nuclear density gauge. With a total of 180 test points, 60 test points were collected from each pavement material. According to the results, the dry density values measured from the nuclear density gauge were much higher than the obtained values from  the sand replacement method, which these results were found to be similar among the three pavement materials. The reading time did not affect the values which were measured from the nuclear density gauge. However, it was found that the dry density values varied with grain sizes. A linear relation and a good coefficient (R²) were found between the nuclear methods and the sand replacement method. These hence ensured, the accuracy of the instrument. From the present study, the nuclear method showed the advantages of speed and repeatability, which can serve the current constructions which require fast construction that come with high quality. Nonetheless, the nuclear gauge equipment, must be calibrated with a reliable method for the confidence of users.