Classifying Aggregates: A Comprehensive Guide

Aggregates are an essential component of any concrete construction project. Knowing the different classifications of aggregates is a great starting point when planning a project. Aggregates can be classified according to shape into rounded, irregular or partially rounded, angular, flaky, and elongated aggregates. Depending on grain size, aggregates are further divided into fine and coarse-grained aggregates.

Rounded aggregates have a completely natural shape and are available in the form of coastal gravel. This aggregate allows for minimum void percentages (32— 33%), making it more workable. Partially rounded aggregates are available in the form of pit sands and gravel and can have about 35 to 37% voids. Irregularly shaped aggregate offers lower workability compared to rounded aggregates.

It has a slightly better bond strength than rounded aggregate, but not as much as is required for high-strength concrete. Angular aggregates provide a high specific area compared to rounded aggregates. With a larger surface area, they show a greater bond strength than rounded aggregates. In addition, the angular aggregate shows a better interlocking property in the concrete that contributes to the strength of the concrete.

Flaky and elongated aggregates are those whose length is greater than its width and the width is greater than its thickness. Aggregates can also be classified based on their source into natural and manufactured aggregates. In this, aggregates are classified based on bulk specific gravity into lightweight, normal weight, and heavy weight aggregates.

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