Fine Aggregate: Definition, Size, Density and Properties

Things You Should Know About Fine Aggregate

Aggregate is the granular material used to produce concrete or mortar and when the particles of the granular material are so fine that they pass through a 4.75mm sieve, it is called fine aggregate. It is widely used in the construction industry to increase the volume of concrete, thus it is a cost saving material and you should know everything about the fine aggregate size, its density and grading zone to find the best material.

Definition of Fine Aggregate

Fine aggregate is the essential ingredient in concrete that consists of natural sand or crushed stone. The quality and fine aggregate density strongly influence the hardened properties of the concrete.

The concrete or mortar mixture can be made more durable, stronger and cheaper if you made the selection of fine aggregate on basis of grading zone, particle shape and surface texture, abrasion and skid resistance and absorption and surface moisture.

Role of Fine Aggregate in Concrete Mix

Fine aggregates are the structural filler that occupies most of the volume of the concrete mix formulas. Depending on composition, shape, size and other properties of fine aggregate you can have a significant impact on the output. The role of fine aggregate can be described in few points:

• Fine aggregates provide dimensional stability to the mixture
• The elastic modulus and abrasion resistance of the concrete can be influenced with fine aggregate
• Fine aggregates quality also influence the mixture proportions and hardening properties
• The properties of fine aggregates also have a significant impact on the shrinkage of the concrete.

Also read: Beginners Guide to Coarse Aggregate

Properties of Fine Aggregates

While making the selection for appropriate aggregate to be used in particular concrete mix, few properties needs to be considered, such as:

• Void content: How much amount of cement paste will be required for the mix eventually depends on the empty spaces between the aggregate particles. Always keep in mind that angular aggregates increase the void content, whereas well-graded aggregate and improved grading decreases the void content.
• Shape and texture: Size and shape greatly influence the quality of the concrete mix. For the preparation of economical concrete mix, you should know that rough-textured, angular, and elongated particles require more water for the formula. However, you will need less water to produce workable concrete when the aggregates are smooth, rounded compact aggregate.
• Absorption and surface moisture: The fine aggregate density depends on the inside solid material and void content, thus you need to measure the absorption rate prior to ensure how much water will be required in the concrete mixture.
• Abrasion and skid resistance: In order to minimize the wear in high traffic areas, such as heavy duty floors and pavements you can consider the relative measure when the fine aggregate is rotated in a cylinder along with some abrasive charge.

Grading Zone of Fine Aggregate

A good concrete mix must include aggregates that are clean, hard, strong and free of absorbed chemicals or coatings of clay and other fine materials. Ignorance of these characteristics can cause the deterioration of concrete, thus regulatory authorities have decided grading zone of fine aggregate, where each zone defines the percentage of fine aggregate passed from the 600 microns sieve size:

1. Zone I: 15% to 34%
2. Zone II: 34% to 59%
3. Zone III: 60% to 79%
4. Zone IV: 80% to 100%

You can assess the quality of fine aggregate with help of the grading zones. However, for precise assessment, you can seek help from experts who are well versed in performing tests for bulk density, bulkage, and specific gravity to find the best in class material.

You may also like to read: Difference between Coarse Aggregate and Fine Aggregate