Aggregates

Aggregates are one of the major constituents of concrete and their properties greatly influence the basic properties of concrete. In this experiment, the moisture content and grading of aggregates are the main issues to be concerned.

The fineness modulus of fine aggregates is an index number which represents the mean size of the particles found in a sand. It is calculated by performing a sieve analysis with standard sieves according to AS 1141.11.1-2009. The cumulative percentage retained on each sieve is added before being subtracted by 100, which gives the value of fine aggregate. Importantly there is no need to determine the finesse modulus of coarse aggregate.

The fineness modulus of fine aggregates varies from 2.0 to 3.5mm. Fine aggregates with fineness modulus more than 3.2 should not be considered as fine aggregates for concrete. Various values of fineness modulus for different sands are detailed in the table below. The size and shape of particles in the fine aggregate alter the workability of concrete. For example, the use of a very fine sand requires more water to be added to achieve the workability that a coarser sand would provide.

Table: Fineness modulus range