Aggregates, both coarse and fine, are frequently utilized to make concrete. The performance of the concrete is affected by the aggregate properties. Also, concrete performance and quality are influenced by aggregate characteristics, aggregate testing procedures, and sample collection methods.
Sieve analysis is a
standard test method used to determine the particle size distribution of
aggregates for concrete and other construction materials. The test involves
passing a sample of aggregate through a series of sieves with different opening
sizes. The amount of aggregate that passes through each sieve is then weighed
and expressed as a percentage of the total sample weight.
In sieve analysis, the
sieve opening is the clear space between adjacent wires in the sieve mesh. The
size of the sieve opening is typically expressed in millimeters (mm) or
micrometers (µm). Sieve openings are standardized by various organizations,
such as the American Society for Testing and Materials (ASTM) and the
International Organization for Standardization (ISO).
Standards developed by
ASTM International (ASTM) are frequently cited. ASTM-officially adopted test
procedures, definitions, and suggested practices, classifications, and
specifications. ASTM C 33 is a common consensus specification for fine and
coarse aggregate for concrete.
Table: Sieves commonly used for sieve analysis of concrete aggregates (ASTM C33)
Coarse sieves
|
Standard sieve designation (ASTM E 11) |
Nominal sieve opening |
||
|
Standard |
Alternate |
mm |
in. |
|
75.0 mm |
3 in. |
75.0 |
3 |
|
63.0 mm |
2-1/2 in. |
63.0 |
2.5 |
|
50.0 mm |
2 in. |
50.0 |
2 |
|
37.5 mm |
1-1/2 in. |
37.5 |
1.5 |
|
25.0 mm |
1 in. |
25.0 |
1 |
|
19.0 mm |
3/4 in. |
19.0 |
0.75 |
|
12.5 mm |
1/2 in. |
12.5 |
0.5 |
|
9.5 mm |
3/8 in. |
9.5 |
0.375 |
Fine sieves
|
Standard sieve designation (ASTM E 11) |
Nominal sieve opening |
||
|
Standard |
Alternate |
mm |
in. |
|
4.75 mm |
No. 4 |
4.75 |
0.1870 |
|
2.36 mm |
No. 8 |
2.36 |
0.0937 |
|
1.18 mm |
No. 16 |
1.18 |
0.0469 |
|
600 μm* |
No. 30 |
0.60 |
0.0234 |
|
300 μm |
No. 50 |
0.30 |
0.0117 |
|
150 μm |
No. 100 |
0.15 |
0.0059 |
Finest sieve normally used for aggregates
|
Standard sieve designation (ASTM E 11) |
Nominal sieve opening |
||
|
Standard |
Alternate |
mm |
in. |
|
75 μm |
No. 200 |
0.075 |
0.0029 |
*1000
µm (micro-meters) = 1 mm.
Sieve openings are
typically measured in millimeters or inches. For example, a sieve with a 2 mm
opening will allow particles that are 2 mm or smaller to pass through, while
particles that are larger than 2 mm will be retained on the sieve.
The size of the sieve
openings is determined by the sieve number. The higher the sieve number, the
smaller the sieve openings. For example, a No. 200 sieve has openings that are
75 micrometers in size, while a No. 4 sieve has openings that are 4.75 mm in
size. The specific sieves used will depend on the size and gradation of the
aggregate being tested.
The sieves should be
clean and free of any damage or debris. They should also be stacked in order of
decreasing opening size, with the largest sieve at the top and the smallest
sieve at the bottom. A pan should be placed at the bottom of the stack to collect
any material that passes through the smallest sieve.
The results of the sieve
analysis are used to determine the gradation of the aggregate. The gradation is
a measure of the distribution of particle sizes in the aggregate. A well-graded
aggregate will have a uniform distribution of particle sizes, which is
important for producing a strong and durable concrete or asphalt mixture.