Large-size aggregates for road construction – a review of standard specifications and test methods

Abstract

Construction aggregates are essential structural components in road structures, whether in unbound form or combined with cement or bitumen. Specifications and test methods for aggregates are standardised, but current standards are limited concerning the maximal aggregate size for which they apply. This paper deals with standard specifications and test methods for large-size road construction aggregates, reviewing a new Norwegian national standard for large-size aggregates. The standard test methods and their validity and applicability for use on large-size aggregates for road construction are evaluated. The differentiation between requirements regarding the rock material (single rocks) and the aggregate product is specifically discussed, as is the specific challenges related to the use of all-in aggregates. Current standards for construction aggregates do not cover all challenges related to description and quality assessment of construction aggregates. Quality assessment is particularly challenging for large-size aggregates, and this topic needs a better description by international standards. Field methods and digital image processing are introduced as solutions for some of the practical challenges related to sampling for large-size aggregates. The new Norwegian standard could be the first step towards a European standard for large-size aggregates.