Aggregate Crushing Test

1) A brief description of the activity
The activity involved the testing of aggregates in a laboratory to determine whether they are suitable for use as aggregates for concrete. The tests involved the use of a Flakiness Index (FI) to define their shape, a grading and Fineness Modulus (FM) to determine their sizes and a 10% Final Aggregate Crushing Test (FACT) to determine their strength. During the laboratory tests the students were required to take notes of what was being said.
2) Importance of properties of aggregates
Aggregates make up about 70% of the volume of concrete (Owens, 2013). They do not react with cement and water; they are present to make a stronger more durable and workable cement mix and are used as filler in the concrete

It refers the proportion of flaky particles within a given sample. (Owens, 2013) The FI involves the use of a flakiness gauge, which is a flat piece of metal with rectangular gaps cut into it; each gap in the gauge represents a different size, measured in millimeters. It is calculated as the percentage of the mass of stone that will pass through gaps of a given width for the appropriate size of the aggregates. (Owens, 2013)Values of the Flakiness Index taken during the laboratory tests are shown in appendix
3.1.4) 10% Final aggregate crushing test (FACT)
The FACT is used to assess the resistance of an aggregate to mechanical degradation and to compare aggregates. These results do not necessarily relate to the compressive strength of concrete made with that aggregate (Afrisam, 2016). Once the crushing has taken place the material is placed into a sieve and the final material is the material that passes through a 2,8mm sieve. If the final material is not exactly 10% of the original mass of material then the test has to be redone until exactly 10% is reached.
All the groups’ results were put into a table and with these results a graph plotting a trend line could be produced. Using this trend line, the FACT results were calculated by solving for x in the trend line equation. This result came to be 367,5

Round aggregates are optimum aggregates to use because the load is distributed over the whole area of the aggregate. Elongated aggregates are weaker than round aggregates because the load is applied at a point of weakness on the aggregate. Aggregates have a FM as low as 0.5 (consists of very fine sand) and have a FM as high as 3.5 or more (consisting of very coarse sands). The medium range of FM lies between 2.4-2.9 thus means that there is a balance between fine and coarse sands