EVALUATION OF THE HOT MIX ASPHALT COMPACTABILITY UTILIZING THE IMPACT COMPACTION METHOD

This study investigates possibility of utilizing an accelerometer to evaluate compactability of Hot Mix Asphalt compacted with an impact hammer. For over 50 years Marshall Asphalt Mix Design has been the principal choice for asphalt mix designers around the world. Although the United States has almost entirely moved to Superpave Mix Design, the rest of the world nations still choose the Marshall Method. The investigation was conducted with the accelerometer placed on the falling mass of the Marshall Hammer and acceleration data was stored and analyzed. Data obtained from the accelerometer was filtered and the asphalt mix response after each blow was analyzed. Results from the study showed that during impact compaction, a so-called locking point exists. This point is defined as the first blow when peak acceleration and impact time become stable. When this point is reached, further compaction has a noticeably lower effect on decreasing air void content. A Superpave Gyratory Compactor was used to confirm the results obtained with the impact hammer, and a correlation was established.