What test is used to check the gradation of composite aggregates in an asphalt mix?

The extraction test is specifically designed to determine the gradation and characteristics of composite aggregates within an asphalt mix. This test involves extracting the asphalt cement from the mixture, allowing for a clear assessment of the aggregate sizes and distributions. By analyzing the extracted aggregate, engineers can evaluate how well the components meet specified gradation requirements, which is crucial for ensuring optimal performance of the asphalt mixture.

Other tests mentioned do not focus specifically on the gradation of aggregates. The compression test evaluates the strength of materials under compression but does not provide information on aggregate size distribution. The drainage test assesses the permeability of asphalt concrete, which relates to water movement, rather than gradation. The cohesion test measures the internal strength of a material but does not directly address the distribution or size of the aggregates in an asphalt mix. Thus, the extraction test is the most relevant method for evaluating the gradation of composite aggregates used in asphalt.