Abrasion Resistance Test on Concrete

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Abrasion resistance of concrete is one of the measures of its durability. The concrete surface deteriorates due to abrasion by sliding, scraping, percussion, or action of abrasive materials carried by water.

The abrasion loss of a specimen exposed to an abrasive charge is used to determine the relative resistance of concrete surfaces in this standard test.

This test method determines the abrasion caused by physical impacts on concrete pavements (roads and airfields), industrial floors, railway platforms, dockyards, and walkways, among other things.

Scope of Abrasion Resistance Test

The scope of the test is to determine the abrasion resistance properties of concrete under physical conditions by impinging it with air-driven silica sand using 10 cm concrete cubes.

Working Principle of Test

An abrasive charge is impinged on the surface of the concrete cubes. As a result, the concrete surface of the cubes abrades, and the consequent loss in mass of the cubes is referred to as concrete abrasion loss.

Apparatus Required for the Test

1. Scale

The scale shall have a minimum capacity of 5000 g. The permissible variation at a load of 5000 g shall be 15 g. 

2. Pneumatic Sand Blasting Cabinet 

1. The pneumatic sandblasting cabinet consists of a wooden cabinet with a tightly closing door, as shown in Figure-1.
2. A high carbon steel nozzle shall fit through the top of the cabinet.
3. The nozzle's length, including the tip, must be 15 cm, and it must be mounted on the cabinet so that the distance between the nozzle's tip and the surface of the concrete sample is 50.02 cm.
4. An annular copper or brass air tube of 0.48 cm in diameter shall be provided inside the nozzle.
5. Beyond the nozzle, the air tube diameter shall change smoothly to a diameter of 1.7 cm.
6. Inside the nozzle, the tube shall end at a distance of 2 cm from the tip of the nozzle.
7. Four holes, each having a diameter of 0.48 cm, shall be provided on the side of the nozzle immediately below the collar for passing sand into the nozzle.
8. Sand is drawn into the nozzle by the suction caused by high air velocity at the nozzle tip.

3. Conical Galvanized Iron Hopper

1. As illustrated in Figure-2, a conical galvanized iron hopper should be placed at the top of the cabinet to store the charge of sand pushed by air pressure.
2. The entire nozzle assembly is secured to the cabinet with a lock nut and washer combination.
3. The copper or brass air tube must be connected with a pressure gauge to properly measure the air pressure as close to the nozzle as feasible.
4. The tube shall be connected to a compressor with a pressure control device giving air supply at a pressure of 0.14 N/mm² as recorded in the pressure gauge.

Abrasive Charge

1. The air pressure-driven charge of sand used for rubbing the concrete surface is termed the abrasive charge. 
2. It shall conform to IS:650-1966* but graded to pass l.00 mm IS sieve and retained on 0.50 mm IS sieve.
3. The charges can be reused after sieving through a 0.50 mm IS sieve.

Test Operating Conditions 

The following test operating conditions shall be followed for determining the abrasion loss of concrete,

1. the operating air pressure must be 0.14 N/mm², 
2. The abrasive charge shall be as stipulated above.
3. The quantity of charge shall be 4000 g for each impingement.
4. The specimen's abrasion loss shall be considered the loss in mass (in grams) after two separate impressions on the same face of the concrete cube. 

Preparation of Test Specimen

1. The 10 cm concrete cube specimens, duly cured for 28 days, shall be placed in an oven at 50°C for 24 hours.
2. The surface of the specimen shall be rubbed with emery paper to remove cement laitance and expose aggregate grains before conducting the test.

Test Procedure

1. The weighted, dry specimen should be placed on the specimen carrier with the surface to be examined facing the nozzle tip (any of the four smoother vertical surfaces of the cube that came in contact with the mold).
2. The nozzle tip shall be placed at the middle of the half side of the cube (2.5 cm away from the edge of the specimen). 
3. The specimen surface shall then be exposed to blast for the full charge of sand (4000 g).
4. The cradle shall be moved slowly between the two fixed points with the help of the handle provided.
5. The test should be performed on the same surface by rotating the sample 180 degrees in the horizontal plane, allowing two imprints to be made on the same surface.
6. After the test is completed, the sample shall be removed, cleaned, and weighed to determine the mass loss in grams for one surface of the sample.
7. The above procedure shall be repeated on the other three vertical surfaces of the same sample specimen.

Test Calculation 

The loss in mass of the specimen for each surface shall be calculated as follows:

m=m₁- m₂

m = loss in mass in g, 
m₁ = mass of the specimen before each test in g,
m₂ = mass of the specimen after each test (on one surface with two impressions) in g.

Suggested Values of Abrasion Loss 

The following maximum abrasion loss values for the different categories of concrete surfacing have been tentatively suggested for broad guidance only.

Sl. No.	Surfacing Category	Maximum values of abrasion loss, Percent loss
1	Concrete Pavement: a) With mixed traffic including iron tyred traffic b) With pneumatic tyred traffic only	0.16 0.24
2	Factory floors	0.16
3	Dockyard	0.16
4	Railway platform	0.24
5	Footpath	0.40

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