How many thickness measurements of HMA specimens are required to determine the average thickness?

To determine the average thickness of Hot Mix Asphalt (HMA) specimens, it is essential to take multiple measurements for accuracy and reliability. By conducting four thickness measurements, the inspector can account for any variations across the surface of the asphalt. This practice is vital because asphalt layers may not be entirely uniform due to factors such as equipment calibration, laying techniques, or material inconsistencies.

Taking a single measurement could lead to an inaccurate representation of the overall thickness, missing any localized variations. Two or three measurements might also not provide a comprehensive view. The use of four measurements allows for a more robust calculation of the average, reducing the impact of outliers or anomalies in any single reading. The average of these four measurements provides a solid foundation for assessing compliance with design specifications and ensuring that the paving meets necessary quality standards.