Abstract
The sampling of hot-mix asphalt (HMA) is an important part of the quality control testing process. The quality of the sample can have a significant effect on the test results. When a sample of HMA is taken, the technician's goal should be to obtain a sample that is representative of the mixture that will be placed on the pavement and is not segregated or contaminated by foreign materials. Several possible choices exist for sampling locations. Samples may be taken from the back of the haul truck at the plant with either a shovel or a robotic sampling device. Samples can be taken at the paving site directly behind the spreader after the mix has been released from the screed but before the first roller has passed over it. Samples can also be taken with cores being cut from the compacted roadway. Each of these methods has its advantages and disadvantages. For this study, samples of two mixes were taken at various locations (truck by shovel, truck by robotic device, behind the spreader, and cores) for a period of several days and tested for asphalt content, gradation, and percent air voids. The results were compared to determine what, if any, effect sampling location has. Overall, although there is little statistical difference in the laboratory properties due to sampling location (except for percent asphalt content), it does appear that segregation may be occurring in the samples obtained from the truck by using a shovel (finer gradation, higher asphalt content, and lower percent air voids). Use of the remote truck sampling device appears to result in properties that more closely match the properties of the mix sampled behind the spreader for Mix 2.
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