The bleeding of concrete can be used to determine the amount of mixing water that will seep out of a fresh concrete mix. This is done through a test that measures the relative quantity of bleeding water. By analyzing the bleeding of the concrete, one can gain insight into the water-cement ratio of the mix and make adjustments accordingly. This test can be a helpful tool for ensuring that the concrete is properly mixed and that the final product will have the desired properties.
Test for Bleeding of Concrete
Apparatus
The apparatus and accessories needed for conducting a bleeding test on concrete include a cylindrical container, a weighing scale, a pipette, a tamping bar, and a graduated cylinder. The cylindrical container is used to hold the concrete sample during the test, while the weighing scale is used to measure the weight of the container and concrete. The pipette is used to collect the bleeding water from the surface of the concrete, while the tamping bar is used to compact the concrete in the container.
Finally, the graduated cylinder is used to measure the volume of the collected bleeding water. These tools are essential for conducting an accurate bleeding test and ensuring the quality of the concrete.
1. Cylindrical Container
A cylindrical container is being used for a test, and it is made of steel. The container has a capacity of 0.01 cubic meters. The cylinder’s inside diameter measures 250 millimeters, while its inside height is 280 millimeters.
2. Weighing Scale
A weighing scale with a high level of accuracy is needed for weighing samples of specimens. Specifically, the scale must be capable of measuring with an accuracy of up to 0.005. This level of precision is necessary to ensure that the measurements of the samples are as accurate as possible. Such a scale would be suitable for use in scientific laboratories, research facilities, or any other setting where precise measurements of specimens are required.
3. Pipette
A pipette is a tool that is specifically designed for drawing off small amounts of liquid from a container. In certain contexts, such as in the field of materials testing, a pipette may be used to draw off the bleed water from a specimen. Bleed water refers to the excess water that is present in a material after it has been mixed, poured, or applied. This water can compromise the integrity of the material and may need to be removed in order to obtain accurate test results. By using a pipette to draw off the bleed water, researchers and technicians can ensure that they are working with a representative sample of the material, free from excess moisture. This can help to improve the accuracy of their tests and ensure that their results are reliable. Overall, the use of a pipette in this context is an important tool for ensuring that materials are properly tested and evaluated.
4. Tamping bar
The tool utilized in the test is known as a tamping bar, which is a type of rounded steel bar with a diameter of 16 mm and a length of 610 mm. Its design consists of a cylindrical shape that enables it to be easily held and utilized by the user. During the testing process, the tamping bar was used as a means of applying pressure to a particular object or material in order to gauge its strength or durability. The specific dimensions of the tamping bar were selected based on their ability to accurately and effectively carry out the required task.
5. Graduated Cylinder
To measure the quantity of water accurately, a graduated cylinder with a volume of 100 cm3 is necessary. The graduated cylinder is a laboratory instrument that is commonly used to measure the volume of liquids. It is a narrow, cylindrical container that is marked with a scale along its length. The scale indicates the volume of liquid contained in the cylinder, allowing for precise measurements to be taken.
When measuring liquids, it is important to use the appropriate equipment to ensure accurate results. A graduated cylinder is an ideal tool for measuring the volume of liquids, as it allows for precise measurements to be taken. In this case, a graduated cylinder with a volume of 100 cm3 is required to measure the quantity of water. This means that the cylinder has a capacity of 100 cubic centimeters, which is the equivalent of 100 milliliters. By using the graduated cylinder, the volume of water can be measured with a high degree of accuracy, making it a valuable tool in laboratory settings.
Test Procedure
To conduct a bleeding test on freshly mixed concrete, it is necessary to start with a sufficient quantity of concrete with a known water content. A cylindrical container is then filled with the concrete mix in 5 layers of 50mm each. After each layer is added, it should be tamped or compacted with a minimum of 60 strokes using a tamping bar. Once the final layer has been added and compacted, the top surface is smoothed and leveled with a trowel.
Immediately after troweling, the time is noted, and the container is weighed. The container should then be placed on a leveled surface free from vibrations, with the top covered or closed to prevent evaporation of bleed water. The test should be conducted at a temperature between 25°C and 29°C.
Water that accumulates on the top surface of the concrete should be drawn off every 10 minutes using a pipette, and collected in a graduated cylinder. This process should be repeated for the first 40 minutes. After 40 minutes, the water should be collected every 30 minutes until bleeding stops. If it is difficult to draw off water from the flat top surface, the container may be slightly tilted to collect the water.
Finally, the weight of water collected in the graduated jar should be noted. By following these steps, a bleeding test can be conducted on freshly mixed concrete to determine the amount of bleed water that is released during the setting process.
Calculations
The equation (1) represents the calculation of the bleeding water percentage in a concrete mix. Bleeding water is defined as the total quantity of water that separates from the concrete mix and accumulates on the surface. It is expressed as a percentage of the total quantity of water in the mix. In other words, it is the percentage of net mixing water that is contained within the test specimen. The numerator, B, represents the total quantity of bleeding water, while the denominator, W, represents the total quantity of water in the concrete mix. By multiplying the ratio of B to W by 100, we obtain the percentage of bleeding water in the concrete mix. This calculation helps to determine the amount of water that is separated from the concrete during the bleeding process, which can have an impact on the quality and properties of the final hardened concrete.
Equation (2), which takes into account the water absorbed by aggregates, is more accurate than equation (1) when calculating the total mass of bleeding water (D) in a concrete mix. In equation (2), the net mass of water (w) is subtracted from the total mass of water in the mix (W), and the result is then divided by the total mass of the concrete mix (S). This allows for a more precise estimation of the total mass of bleeding water, as it considers the water absorbed by aggregates, which can affect the overall water content in the mix. In contrast, equation (1) does not account for water absorbed by aggregates, making equation (2) a more reliable option for calculating bleeding water mass in concrete mixes.
Result
Bleeding water percentage for the given concrete mix = _______ %