Correct option is B
Los angeles abrasion test is a preferred test for examination of hardness property of the aggregates
and has been standardized in India (IS 2386: Part IV). Abrasion resistance is the property of aggregates by virtue of which they resist surface wear and scratches caused due to rubbing action of another surface or material.
The hardness test is of the following type:
1) Los Angeles abrasion test
2) Devel abrasion test
3) Dorry abrasion test
Los Angeles Abrasion Test:-The principle of the Los Angeles Abrasion Test is to find the percentage wear due to relative rubbing action between the aggregate and steel balls used as an abrasive charge. Los Angeles machine consists of circular drum of internal diameter 700 mm and length 520 mm mounted on a horizontal axis enabling it to be rotated. An abrasive charge consisting of cast iron spherical balls of 48 mm diameters and weight 340-445g is placed in the cylinder along with the aggregates.
• The cylinder is then locked and rotated at the speed of 30-33 rpm for a total of 500-1000 revolutions depending upon the gradation of aggregates. After specified revolutions, the material is sieved through 1.7 mm sieve and passed fraction is expressed as percentage total Weight of the sample.
• This value is called the Los Angeles abrasion value. A maximum Value of 40 percent is allowed for WBM base course m Indian conditions. For Bituminous concrete, a maximum value of 35 percent is specified.
