DESCRIBE THE PROPERTIES OF ( FINE AND COARSE ) AGGREGATES ?
Aggregates are defined as a combination of distinct parts gathered into a mass or a whole. They can increase stability of a structure and protect it from bad weather. In addition, aggregates can also increase quality and reduce price of the cements beacause of their greater volume stability and filling function. Therefore, it is important for civil engineers to understand properties of aggregates. Aggregates’ properties are the characteristics of both the individual paticles and the characteristics of the combined material.The followings are main properties: * Particle Shape and Surface Texture :
* Particle shape determines how the material will pack into a dense configuration and the mobility of stones within a mix. * Aggregate particles with angular shape creates bulk materials with better stability than rounded ones. However, angular shape makes particles slide difficultly across each other so this creates the disadvantage in work with angularity and flakiness. * Rough texture improves bonding and increases interparticle friction but there is a diificulty to compact rough aggregates into a dense configuration than smooth aggregates. * Rounded and smooth aggregate particles improve the workability of fresh concrete during mixing so they are good for preparing portland cement concrete. * Angular and rough particles are good for asphalt concrete and base courses because they increase increase the stability of the materials in the field and reduce rutting. * Flaky and elongated aggregates are difficult to compact during construction and are easy to break so they are should not be used for asphal concrete. * Soundness and Durability:
* Soundness or Durability is the ability of aggregate to withstand weathering. * The soundness by freeze thaw (AASHTO T103) and potential expansion from hydrated reactions (ASTM D4792) are alternative screening tests for...
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