How to determine split tensile strength test of concrete || Laboratory Concrete Test #2

Anime_Edu - Civil Engineering Videos

26 Aug 201802:45

Summary

TLDRThe video explains the procedure for conducting split tensile strength tests on concrete cylinders. The test measures tensile strength by applying a compressive force along the cylinder's length using a universal testing machine. The concrete specimen is prepared, cured, and tested at different intervals (7, 14, and 28 days). Load is applied continuously until the cylinder fails, and the split tensile strength is calculated using a specific formula. The video also highlights the setup process, including aligning bearing strips and noting the load at which failure occurs.

Takeaways

🔍 The split tensile strength test measures the tensile strength of concrete using a compressive force along the length of a concrete cylinder.
🧱 The test specimen is a cylindrical concrete sample with dimensions of 150 mm in diameter and 300 mm in length.
🛠️ A universal testing machine is used to perform the split tensile strength test.
📏 The concrete specimen is prepared in layers, with each layer tamped 25 times to ensure compaction.
💦 After a day, the mold is removed and the specimen is placed in a curing tank at 27 ± 2°C for a specified period.
⏲️ Specimens are tested after curing for 7, 14, or 28 days depending on the requirements.
✍️ The weight and dimensions of the specimen are recorded before testing, and markings are drawn on the surface for alignment.
📐 The specimen is placed in the testing machine with plywood bearing strips on both sides, and optionally supplement bars depending on the diameter.
📈 Load is applied continuously at a rate between 1.2 to 2.4 MPa per minute until the cylinder fails, creating cracks.
📝 The split tensile strength is calculated using the formula: 2P / (π * D * L), where P is the load at failure.

Q & A

What is the purpose of the split tensile strength test on concrete?
-The split tensile strength test is used to determine the tensile strength of concrete by applying a compressive force along the length of a cylindrical concrete specimen.
What are the dimensions of the cylindrical specimen used in this test?
-The cylindrical specimen has a diameter of 150 millimeters and a length of 300 millimeters.
Which equipment is used for conducting the split tensile strength test?
-The Universal Testing Machine (UTM) is used to conduct the split tensile strength test.
How is the concrete specimen prepared for the split tensile strength test?
-The specimen is prepared by placing the concrete mixture in layers inside a mold and tamping each layer with 25 blows. After 24 hours, the mold is removed, and the specimen is placed in a curing tank at 27 ± 2°C.
At what intervals are the specimens tested after being placed in the curing tank?
-The specimens are tested at intervals of 7, 14, and 28 days after being removed from the curing tank.
How is the specimen placed in the Universal Testing Machine for the test?
-The specimen is placed longitudinally in the machine, with bearing strips made of plywood placed on both sides. It is then aligned according to the marked lines on the specimen.
What is the loading rate applied during the split tensile strength test?
-The load is applied continuously at a rate within the range of 1.2 to 2.4 MPa per minute.
How is the split tensile strength of the concrete calculated after the test?
-The split tensile strength is calculated using the equation 2P / (π × D × L), where P is the load at which the specimen fails, D is the diameter, and L is the length of the specimen.
Why are supplement bars sometimes used during the test?
-Supplement bars are sometimes placed on top of the plywood bearing strips depending on the diameter of the specimen to ensure even distribution of the applied load.
What factors could affect the results of the split tensile strength test?
-Factors that can affect the test results include improper specimen preparation, incorrect curing temperatures, variations in the load application rate, and misalignment of the specimen in the testing machine.

Outlines

00:00

🧪 Introduction to Split Tensile Strength Test

This section introduces the split tensile strength test for concrete. It explains that the tensile strength is determined by applying a compressive force along the length of a cylindrical concrete specimen. The cylinder used has a diameter of 150 mm and a length of 300 mm, and the test is performed using a universal testing machine.

🔧 Preparation of the Test Specimen

Here, the procedure for preparing the concrete specimen is described. The specimen is molded in layers and each layer is tamped with 25 blows. After one day, the mold is removed and the specimen is placed in a curing tank at a controlled temperature of 27 ± 2°C. The specimen is kept in the tank for 7, 14, or 28 days, depending on the test requirement.

📝 Marking and Weighing the Specimen

This part focuses on the preparation for the actual test. The line marking on the specimen, as shown in the video, is explained. The weight and dimensions of the specimen are recorded before proceeding with the test. The specimen is positioned longitudinally in the testing machine with plywood bearing strips placed on both sides for alignment.

⚖️ Applying Load and Measuring Strength

The test process begins with applying a continuous load to the specimen at a rate of 1.2 to 2.4 MPa per minute. The load is applied until the cylinder develops cracks and fails. The split tensile strength is calculated using the equation 2P/πDL, where P is the load at failure.

🎬 Conclusion and Call to Action

This final segment concludes the video, encouraging viewers to like, share, comment, and subscribe to the channel for more content. It also hints that more informative videos are coming soon.

Mindmap

Keywords

💡Split tensile strength test

The split tensile strength test is a method used to measure the tensile strength of concrete by applying compressive force along its length. This test helps determine how well the concrete can resist tension, which is crucial for its structural integrity. In the video, this concept is central as it describes the process and purpose of the test, involving a cylindrical specimen.

💡Concrete cylinder

A concrete cylinder is the standard specimen used in tensile strength tests. It typically has a diameter of 150 millimeters and a length of 300 millimeters. This cylindrical shape is important because it evenly distributes the force applied during testing. The video references this when explaining the specimen's size and preparation.

💡Compressive force

Compressive force refers to the force applied to an object that reduces its size by pressing it together. In the context of this video, the force is applied longitudinally to the concrete cylinder to test its tensile strength. This helps simulate real-world conditions where concrete might experience similar forces in structures.

💡Universal testing machine

The universal testing machine (UTM) is an apparatus used to apply controlled forces to a material and measure its response. In the video, it is used to apply the compressive force to the concrete cylinder during the tensile strength test. The UTM plays a critical role in ensuring that the load is applied consistently for accurate results.

💡Specimen preparation

Specimen preparation refers to the process of creating the concrete sample used in testing. It involves placing the material in a mold, tamping it with 25 blows per layer, and curing it. This step ensures that the concrete is properly formed and cured before testing. The video highlights this as a necessary procedure for obtaining accurate results.

💡Curing tank

A curing tank is a controlled environment used to store concrete specimens at specific temperatures and humidity levels to ensure proper curing. In the video, the concrete is placed in a curing tank at 27 ± 2 degrees Celsius to allow it to strengthen before testing. Proper curing is vital for the concrete to achieve its maximum strength.

💡Bearing strip

A bearing strip, often made of plywood, is placed on both sides of the concrete specimen to ensure even distribution of force during testing. In the video, this strip is important because it helps align the specimen in the universal testing machine, which ensures that the applied force is accurate and the test results are valid.

💡Load application rate

The load application rate is the speed at which force is applied to the specimen. In the video, it is specified as a range between 1.2 to 2.4 MPa per minute. This controlled application ensures that the force is applied gradually, allowing for a precise measurement of when the concrete fails.

💡Cracks

Cracks refer to the visible signs of structural failure in the concrete specimen. In the video, the load is applied until the concrete cylinder develops cracks, indicating that it has reached its tensile strength limit. Observing these cracks helps determine the load at which the material can no longer hold together.

💡Tensile strength equation

The tensile strength equation, represented as 2P / (πDL), is used to calculate the split tensile strength of the concrete. P represents the load at which the specimen fails, while D and L are the dimensions of the cylinder. This formula is crucial for interpreting the results of the test. The video concludes by explaining how to use this equation to calculate the strength of the concrete.

Highlights

The split tensile strength test on concrete measures tensile strength by applying compressive force along the length of a concrete cylinder.

The concrete cylinder used in the test is 150 millimeters in diameter and 300 millimeters in length.

The universal testing machine is used to conduct the split tensile strength test.

The concrete specimen is prepared using standard manufacturing procedures and placed in layers, with each layer tamped using 25 blows.

After one day, the mold is removed, and the specimen is placed in a curing tank at a temperature of 27 ± 2 degrees Celsius.

The specimen is tested for tensile strength at intervals of 7, 14, and 28 days after curing.

A line is drawn on the specimen before testing, and its weight and dimensions are recorded.

The specimen is placed longitudinally in the testing machine with a plywood bearing strip on both sides.

In some cases, supplement bars are placed on top of the plywood based on the diameter of the specimen.

The load is applied continuously at a rate between 1.2 to 2.4 MPa per minute.

The test records the load at which the concrete cylinder fails by developing cracks.

The split tensile strength is calculated using the formula: 2P / (πDL), where P is the load at which the specimen breaks.

The split tensile strength test provides critical data for understanding the tensile behavior of concrete under compressive forces.

Curing temperature control and timing (7, 14, and 28 days) significantly influence the concrete's tensile strength.

This method is commonly used to evaluate concrete’s durability and performance in various structural applications.