A framework for a coarse aggregate classification system

Abstract

Coarse aggregates are the major constituents of concrete or asphalt mixtures and are widely used in various construction purposes. A classification system for these aggregates would provide a systematic means of aggregate identification which could be used in the selection of aggregates for different construction activities. The objectives of this research were: (1) to characterize the aggregates based on their properties (2) to develop a framework for an Aggregate Classification System (3) to provide basis for implementation of the classification system and (4) to recommend and list test procedures and equipment needed to carry out the tests on aggregates. Extensive field and laboratory investigations have been carried to study the performance of pavements made with different types of coarse aggregates and the properties which affected the performance have been incorporated in the aggregate classification system. The framework for the classification system is developed based on various physical, chemical, mechanical and thermal properties of aggregates. The classification system is developed in two stages: (1) A comprehensive system of aggregate classification incorporating all significant aggregate properties affecting performance and (2) A simplified version is arrived at from the first stage classification system. The classification system is recommended for implementation at three levels. The first level of implementation consists of aggregate identification and the second level provides detailed aggregate evaluation. The third level is aimed at supplementing the findings of the first two levels by providing a detailed evaluation of aggregates as needed. The basic tests recommended for aggregate evaluation are discussed and the required equipment for these tests are also listed. Aggregate properties and respective performance indicators are tabulated. Various areas of further research are identified and recommendations are made for implementation of the proposed classification system.