Asphalt Technology News

The National Center for Asphalt Technology (NCAT) completed a roundrobin study in March to determine the accuracy and precision of the NCAT asphalt content tester. The Center has conducted research since 1990 to develop this test method for determining asphalt content of hot mix asphalt (HMA) mixtures by ignition (See the fall, 1994, issue of Asphalt Technology News). In the ignition method, a sample of HMA mixture (about 1,200 grams) is subjected to 538°C ( 1000”F) in a furnace to ignite and burn the asphalt cement from the aggregate. NCAT’S work has resulted in a test procedure and equipment that automatically measures the asphalt content in 30-40 minutes. The gradation of the aggregate can then be determined using standard sieve analysis. A larger HMA sample size (2,400 grams) can also be tested. The HMA test sample is divided into two portions and placed in two stainless steel No. 8 mesh trays which are stacked on top of each other in the furnace of the NCAT asphalt content tester. The unit has a built-in scale with a digital readout underneath the furnace to weigh the HMA sample continuous y during ignition. A built-in printer prints the asphalt content on completion of the test. After equipment for the procedure was developed by Barnstead Thermolyne, 12 units of the NCAT asphalt content tester were purchased for round robin testing to determine the accuracy and precision of (Continued on page 2)