Abrasion resistance is an important measure of concrete durability, as it determines how well the concrete surface can withstand wear and tear from various sources such as sliding, scraping, percussion, or abrasive materials carried by water. The abrasion loss of a concrete specimen when exposed to an abrasive charge is commonly used as a standard test to assess the relative resistance of concrete surfaces to abrasion. This test helps determine how well the concrete can withstand abrasion and maintain its integrity over time.
Effect of abrasion on concrete
This test method is designed to assess the abrasion caused by physical impacts on various types of concrete pavements, including those used for roads, airfields, industrial floors, railway platforms, dockyards, walkways, and more. It is commonly employed to measure the wear and tear that these surfaces may experience over time due to traffic, footfall, or other forms of use. By subjecting concrete samples to controlled impacts, this test method provides valuable information about their durability and resistance to abrasion, helping engineers and practitioners evaluate their performance and make informed decisions about their suitability for different applications.
Scope of Abrasion Resistance Test
The purpose of the test is to evaluate the abrasion resistance characteristics of concrete in real-world scenarios by subjecting it to air-propelled silica sand. The test will be conducted on 10 cm concrete cubes.
Working Principle of Test
Concrete abrasion loss refers to the reduction in mass of concrete cubes when an abrasive charge is applied to their surface. This is achieved through the abrasion of the concrete surface, which is caused by the impingement of the abrasive charge. In other words, the concrete cubes undergo a process of abrasion as a result of the application of the abrasive charge, leading to a loss of mass. This process is commonly used to measure the durability of concrete and to assess its ability to withstand wear and tear.
Apparatus Required for the Test
1. Scale
The requirement is for a scale that has a minimum capacity of 5000 grams. Additionally, the permissible variation at a load of 5000 grams must be 15 grams.
2. Pneumatic Sand Blasting Cabinet
The pneumatic sandblasting cabinet is made of wood and has a door that fits tightly. The cabinet has a high carbon steel nozzle that fits through the top, and the length of the nozzle, including the tip, is 15 cm. The nozzle must be positioned so that the distance between its tip and the surface of the concrete sample is 50.02 cm. An annular copper or brass air tube, which is 0.48 cm in diameter, is located inside the nozzle. The air tube diameter increases smoothly beyond the nozzle to a diameter of 1.7 cm. Inside the nozzle, the tube terminates 2 cm from the tip. The nozzle has four holes, each with a diameter of 0.48 cm, located on its side just below the collar to allow sand to pass into the nozzle. Sand is drawn into the nozzle through the suction created by high air velocity at the nozzle tip.
3. Conical Galvanized Iron Hopper
A conical galvanized iron hopper is required to be placed at the top of the cabinet to store the sand that is pushed by air pressure. This is depicted in Figure-2. The nozzle assembly needs to be secured to the cabinet with a lock nut and washer combination. To accurately measure the air pressure as close to the nozzle as possible, the copper or brass air tube must be connected with a pressure gauge. This gauge will enable the pressure to be measured with precision.
It is important that the air tube is connected to a compressor with a pressure control device. This device will provide air supply at a pressure of 0.14 N/mm2 as recorded in the pressure gauge. This ensures that the required air pressure is consistently supplied to the system.
Abrasive Charge
The charge of sand used to rub the surface of concrete, which is driven by air pressure, is known as the abrasive charge. According to IS:650-1966*, this charge must meet certain standards, and it should be graded to pass through the 1.00 mm IS sieve while being retained on the 0.50 mm IS sieve. If the abrasive charge is filtered through a 0.50 mm IS sieve, it can be reused.
Test Operating Conditions
To determine the abrasion loss of concrete, it is necessary to adhere to specific test operating conditions. The operating air pressure must be precisely 0.14 N/mm2, and the abrasive charge must meet the stipulated requirements. Additionally, it is essential to use a charge quantity of precisely 4000 g for each impingement.
The abrasion loss of the specimen will be measured as the loss in mass, expressed in grams, after two separate impressions on the same face of the concrete cube. These impressions must adhere to the aforementioned test operating conditions to ensure accurate and reliable results. By following these conditions, researchers and professionals can accurately determine the abrasion loss of concrete specimens and make informed decisions about their structural integrity and durability.
Preparation of Test Specimen
The given context states that 10 cm concrete cube specimens need to be prepared and cured for a duration of 28 days. Once the curing is complete, the specimens should be placed in an oven at a temperature of 50°C for 24 hours. After the specified time has elapsed, the surface of the specimens needs to be rubbed with emery paper. This process is necessary to remove any cement laitance that may have formed on the surface during curing. The rubbing also exposes the aggregate grains present on the surface of the specimens. Once this process is complete, the specimens are ready for testing.
Test Procedure
To conduct a sandblasting test on a weighted, dry specimen, it should be placed on the specimen carrier with the surface that needs examination facing the nozzle tip. The cube that came in contact with the mold can be used, and any of its four smoother vertical surfaces can be chosen. The nozzle tip must be positioned at the center of the half side of the cube, 2.5 cm away from the specimen’s edge.
The specimen’s surface should then be exposed to the full charge of sand, which is 4000 g. The cradle should be moved slowly between the two fixed points, with the help of the handle provided. To ensure consistency, 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.
Once the test is completed, the sample should be removed, cleaned, and weighed to determine the mass loss in grams for one surface of the sample. This procedure should be repeated on the other three vertical surfaces of the same sample specimen.
Test Calculation
To calculate the loss in mass of a specimen for each surface, a specific formula must be used. This formula involves subtracting the mass of the specimen after each test (on one surface with two impressions) from the mass of the specimen before each test. The result of this calculation will be the loss in mass, which is measured in grams. The variable “m” represents the loss in mass, while “m1” represents the mass of the specimen before each test and “m2” represents the mass of the specimen after each test. By using this formula, it is possible to accurately determine the amount of mass that has been lost from the specimen during the testing process.
Suggested Values of Abrasion Loss
Tentative maximum abrasion loss values have been suggested for different categories of concrete surfacing. These values are meant to provide 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 |
FAQs
What is the scope of the abrasion resistance test on the concrete?
The objective of the test is to assess the abrasion resistance characteristics of concrete under specific physical conditions. To achieve this, 10 cm concrete cubes will be subjected to impingement with air-driven silica sand. The aim is to observe how the concrete withstands the abrasive action of the sand, which will help in determining the durability of the concrete material.
What is the formula for calculating the loss of mass in the abrasion resistance test on the concrete?
To calculate the loss in mass of a specimen for each surface, the following formula should be used: m = m1 – m2. Here, ‘m’ refers to the loss in mass in grams, ‘m1’ refers to the mass of the specimen before each test in grams, and ‘m2’ refers to the mass of the specimen after each test (on one surface with two impressions) in grams.
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