Theory

The elongation index of the aggregate is defined as the percentage by weight of the particles of aggregate whose greatest dimension is greater than 1.8 times their mean dimensions. It assesses the percentage by weight of particles in an aggregate sample that are elongated or have a length significantly greater than their width. The elongation index provides information about the surface texture of the aggregate particles.

The elongated particles may result in cracks in the pavement since they get broken down easily upon being subjected to heavy loads. Also, the elongated particles have a high ratio of surface area to volume. It may lead to difficulties in achieving a well-compacted mix and can result in increased voids, affecting the overall performance of the construction material. Therefore, it is important to determine the elongation index value of aggregates before using them at the site.

Monitoring the elongation index is part of quality control procedures in the production of concrete. It helps ensure that the aggregates used in construction projects have the desired shape characteristics for optimal performance. The elongation index of course aggregates for pavement should not exceed 15%.

   Elongation index= (Weight of aggregate passing through elongation gauge)/(Total weight of sample taken) ×100 
          

The elongation index of course aggregates for pavement should not exceed 15% .