Los Angeles abrasion test
Los Angeles abrasion test conducted to measure the resistance of aggregates to deterioration by impact, abrasion and grinding. The deterioration due to impact, abrasion, and grinding determined by measuring the percentage of wear due to relative rubbing action between aggregates and steel balls inside a drum rotating at a specific speed.
the test apparatus includes balance, sieves (80, 63, 50, 40, 25, 20, 12.5, 10, 6.3, 4.75 (as per gradation of aggregate) and 1.7 mm), Los Angeles abrasion machine and abrasion charges.
· the grade of aggregates will be determined by the sieving of the aggregate sample. The table no:1 shows the different grades of aggregate according to gradation.
· The test sample shall be clean and dried in an oven at 105 to 110 c˚. The grading of the aggregate shall conform to one of the grading shown in table no:1. The grading of aggregates shall be similar to the grading of aggregates used at work.
· The samples and charges shall be placed inside the Los Angeles abrasion machine. The machine rotates at a speed of 30 to 33 rev/min. the machine shall rotate 500 revolutions for aggregates with grading A, B, C and D. for grading E, F and G, the machine shall rotate 100 revolutions. The table no:2 showing the grading and the corresponding number of charges (steel balls) to be used.
· After the completion of the required number of revolutions. The aggregates shall be discharged from the Los Angeles abrasion machine. The aggregates sample shall be sieved on sieve 1.70 mm. material coarser than 1.70 mm shall be washed and dried at oven at 105 to 110 c˚ until the weight of this material becomes constant.
· Aggregate abrasion value determined by measuring the difference in weight of the original sample and the final weight of the sample expressed as a percentage of the original sample.
Aggregate abrasion value=((A-B)/A)%
A = weight in gm of the oven-dried sample.
B = weight in gm of fraction retained on 1.70 mm Sieve after washing and oven-dried up to constant weight.