Concrete aggregates are composed of geological materials such as gravel, sand and crushed rock. The particle size determines whether it is a coarse-grained aggregate (e.g., gravel) or a fine aggregate (e.g., the resulting concrete can be used in its natural state or crushed, according to its use and application. Email address required Invalid email address Invalid email address ACI Resource Center Southern California Midwest The page may have been updated, moved or deleted. Also be sure to check your spelling.
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A track record of good performance of a local aggregate also provides an indication of the performance of the material in service. Recycled concrete will have a higher absorption and a lower specific gravity than conventional aggregates. Concrete Mix Design and Control, Portland Cement Association (see Chapter 5, Aggregates for Concrete). Recycled aggregates are also used as a partial substitute for natural aggregates in composite materials.
The fundamental relationship between the water-cement ratio and strength begins with the correction of the contribution or absorption of moisture by aggregates. The aggregate comprises large chunks of material in a composite, commonly coarse-grained gravel or crushed rocks and fine materials. OD monitors the moisture content of coarse-grained and fine aggregates on a regular basis to promote consistency and uniformity from batch to batch. If there is a deficiency in a locally available fine aggregate, concrete may benefit from the addition of air entrainment, additional cement, or a supplemental cementitious material (SCM) to address these deficiencies.
Aggregates must be solid, clean, hard, durable, and free of excessive fines or contaminants that could affect cement hydration or alter the paste-aggregate bond. Make sure your concrete producer purchases good quality aggregates, as verified by regular aggregate test results in accordance with ASTM C 33, Standard Specifications for Concrete Aggregates. Leveling limits and maximum aggregate size are specified because these properties affect the amount of aggregate used, as well as cement and water requirements, workability, pumpability, and concrete durability. This is a summary of the most important factors to consider when selecting and dosing concrete aggregate.
As a natural material, the aggregate will sometimes include worn or unstable particles in the supplied product. But a closer look reveals the primary role and influence that aggregate plays on the properties of fresh and hardened concrete. Once processed, aggregates are handled and stored to minimize segregation and degradation and prevent contamination. Aggregate refers to the constituent of a composite material that resists compressive load and provides bulk to the composite material.
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