Survey of hard rock aggregate resource and performance-related problems in New Zealand

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Coote, T.P.; Hancox, G.T.; Perrin, N.D.; Read, S.A.L. 1994 Survey of hard rock aggregate resource and performance-related problems in New Zealand. Lower Hutt: Institute of Geological & Nuclear Sciences Institute of Geological & Nuclear Sciences science report 94/10 52 p.

Abstract: A nationwide survey of hard rock aggregate producers and users has been undertaken to assess resource and performance-related problems, and to identify appropriate directions and priorities for future hard rock aggregate research in New Zealand. This report presents a detailed analysis of the results of the nationwide survey, and investigates whether or not studies of aggregate mineralogical and geotechnical properties will enhance our understanding of the causes of aggregate performance-related problems. New Zealand hard rock aggregates are used mainly for road construction, concrete aggregate, general rockfill and rip rap applications. Crushed alluvial and quarried greywacke are the most common rock types used for aggregate production in NZ due to their abundance, wide distribution, and durability characteristics. The most frequently quarried volcanic rock types are also favourable for aggregate production. Aggregate instability (material breakdown) is the main performance-related problem resulting in a reduction of the effective lifespan of the aggregate. Volcanic and limestone aggregates are prone to material breakdown due to inherent adverse rock material properties. The presence of clays and other deleterious minerals can also significantly impair aggregate performance. Aggregate production is constrained by achieving the correct fines content proportion, which is a general problem nationwide for all types of alluvial and quarry aggregates. (auth)