Comparison of practice for aggregate use in road construction — results from an international survey
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Conventional flexible pavement structures are constructed using aggregates, in a combination of unbound and bitumen bound materials. Crushed rock aggregates are fundamental for road construction in many countries. This paper presents the results of a survey examining differences in the use of aggregates for road construction in 18 countries. The purpose of the study is to gain knowledge about the varying practices for aggregate use and pavement design, to enable better interpretation of international research on this topic. The results confirm that crushed rock is the standard material used in road construction. The aggregate market is international; the aggregate industry in e.g. Norway produces aggregates for both export and domestic use. Pavement materials are regulated through international standards, provided by e.g. CEN and ASTM, in combination with national standards and requirements. The international standards do not set direct requirements; they provide a common system for classification of road materials. The comparison of typical flexible pavement structures in different countries shows that even though the materials overall meet equivalent standards; the practices for material use are divergent. There are considerable differences in both pavement thickness and aggregate size used in the studied countries. In the current situation, traditional physical quality tests dominate aggregate choice. Functional aggregate testing could increase aggregate utilization.