This test is used for determination of effect of impact to coarse aggregate. Generally in Roads and High ways, Often it happens that a very big amount of load act on a surface by impaction. So it is important to find if the aggregate has enough strength to resist against the abrasion and impact. Generally this method is used for aggregate smaller than 37.5 mm sizes.
1.Los Angeles Machine 2.Sieves 3.Balance 4. Pan 5. Standard Steel Sphere
Obtain the sample according to (Sampling Page), and try to reduce it mass to be desired weight with splitting and quartering.
Wash the reduced sample and oven dry at 110±5° Until it reach to constant mass ,separate the sample into fraction sizes described the Table No 1,and mix them to get the grading described in Table 1 .after recombining record the mass of sample to the nearest value of 0.1 Gr.
Table No 1 -Grading of test samples
| Sieve sizes (Square opening) | Mass of Indicated Sizes (Gr) | ||||
| Passing From sieve | Retaining on sieve | Grading | |||
| A | B | C | D | ||
| 37.5mm(1.5 in) | 25mm(1 in) | 1250±25 | ... | ... | ... |
| 25mm(1 in) | 19mm(3/4 in) | 1250±25 | ... | ... | ... |
| 19mm(3/4 in) | 12.5mm(1/2in) | 1250±25 | 2500±10 | ... | ... |
| 12.5mm(1/2in) | 9.5mm(3/8 in) | 1250±25 | 2500±10 | ... | ... |
| 9.5mm(3/8 in) | 6.3mm(3/4in) | ... | ... | 2500±10 | ... |
| 6.3mm(3/4in) | 4.75mm(No 4) | ... | ... | 2500±10 | 2500±10 |
| 4.75mm(No 4) | 2.36mm(No 8) | ... | ... | ... | 2500±10 |
| Total | 5000±10 | 5000±10 | 5000±10 | 5000±10 | |
The table Below is showing No of Spheres Using for test , depending on Grading of aggregate (sample), explained above.
Table No 2 -No of Spheres using the test depending to Grading of Sample
| Grading | Number of Spheres | Mass of Charge (sample) Gr. |
| A | 12 | 5000±25 |
| B | 11 | 4584±25 |
| C | 8 | 3330±20 |
| D | 6 | 2500±15 |
Place the sample and the specified Spheres in Los Angeles testing Machine, and rotate it at speed of 30-33 revelation per minute, for 500 cycles. After mentioned cycles remove the sample from machine and do a preliminary separation of particles sizes which retain on sieve 1.7 mm (No 12).then again sieve the materials finer than 1.7 mm (No120) and .then wash all materials retained on sieve No 12 ,carefully wash them and dry in 110±5° until reaching a constant mass. Then determine the mass of sample to the nearest 1 gr.( if the material using for test is free from dust it is not necessary to wash that after doing test, but it must not affect the amount more than 0.2% of total amount, other wise washing is obligatory.
the calculation is very simple, find deference between initial amount of sample and amount of sample after the test. divide the result by initial value of the aggregate. the final value represent the percentage of loss the aggregate by impaction. Here is a Photo Procedure of test
Report the result as follow:
1. identification the source of aggregate ,type of material and maximum nominal size.
2. Report the Grading designation of sample according to Table 1
3.And Finally the loss by abrasion and impact of sample expressed to the nearest 1% of total mass.
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