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CONCRETE ABRASION TESTING MACHINE
 
 CONCRETE ABRASION TESTING MACHINE

(LOS ANGELES)

(ANALOGUE & DIGITAL MODEL)

i) To determine the Los Angeles abrasion value.

(ii) To find the suitability of aggregates for use in road construction.

IS : 2386 (PART IV ) ASTM : C 131

SPECIFICATION:

This machine is for determining are resistance to bear of small size Course Aggregate and Crushed rock the machine consistence of a hollow cylinder mounted one sturdy frame on ball bearings a detachable shelf which extends which stand through out the inside length of the drum catches the abrasive charge and dose not allow its two fall on the cover the drum is rotated at a speed of 30-33RPM by an electric motor through a heavy duty reduction gear motor is suitable for operation on 220Volts-50Hz, 1ph

Supplied complete with a tray for collection of the materials with abrasive charge

ABRASIVE CHARGE: Consists of set of 12 hardned steel ball of 48mm dia

THEORY:

The aggregate used in surface course of the highway pavements are subjected to wearing due to movement of traffic. When vehicles move on the road, the soil particles present between the pneumatic tyres and road surface cause abrasion of road aggregates. The steel reamed wheels of animal driven vehicles also cause considerable abrasion of the road surface. Therefore, the road aggregates should be hard enough to resist abrasion. Resistance to abrasion of aggregate is determined in laboratory by Los Angeles test machine. The principle of Los Angeles abrasion test is to produce abrasive action by use of standard steel balls which when mixed with aggregates and rotated in a drum for specific number of revolutions also causes impact on aggregates. The percentage wear of the aggregates due to rubbing with steel balls is determined and is known as Los Angeles Abrasion Value.

 

PROCEDURE:

The test sample consists of clean aggregates dried in oven at 105° – 110°C. The sample should conform to any of the gradings shown in table 1.

(i) Select the grading to be used in the test such that it conforms to the grading to be used in construction, to the maximum extent possible.

 

(ii) Take 5 kg of sample for gradings A, B, C & D and 10 kg for gradings E, F & G.

(iii) Choose the abrasive charge as per Table 2 depending on grading of aggregates.

(iv) Place the aggregates and abrasive charge on the cylinder and fix the cover.

(v) Rotate the machine at a speed of 30 – 33 revolutions per minute. The number of revolutions is 500 for gradings A, B, C & D and 1000 for gradings E, F & G. The machine should be balanced and driven such that there is uniform peripheral speed.

(vi) The machine is stopped after the desired number of revolutions and material is discharged to a tray.

(vii) The entire stone dust is sieved on 1.70 mm IS sieve.

(viii) The material coarser than 1.7mm size is weighed correct to one gram.

RESULT:

Los Angeles Abrasion Value =

RECOMMENDED VALUE:

 Los Angeles test is commonly used to evaluate the hardness of aggregates. The test has more acceptability because the resistance to abrasion and impact is determined simultaneously. Depending upon the value, the suitability of aggregates for different road constructions can be judged as per IRC specifications as given: