Determination of Crushing Value of Aggregate
Introduction
The combination crushing cost offers a relative degree of the resistance of an aggregate crushing underneath step by step carried out compressive load. Good quality aggregates should have comparatively crushing value.
The Crushing Value test measures the ability of an aggregate to resist crushing under a compressive load. It is a measure of the strength and toughness of the aggregate. In this test, a standard crushing load is applied to a prepared aggregate sample, and the percentage of fines generated after the specified amount of crushing is determined. A lower crushing value indicates stronger and more durable aggregate.
Significance
The crushing value of aggregate is an essential parameter in assessing the strength and durability of construction materials. It determines the ability of aggregates to resist crushing under a compressive load, which is crucial for their suitability in road construction and concrete production. This experiment aims to determine the crushing value of aggregate samples and provide valuable information for quality control and material selection in civil engineering projects.
Standard
The experiment follows the guidelines outlined in British Standard (BS: 812) Part 110: 1990 – Testing aggregates. Methods for determination of mixture crushing value (ACV).
Scope
The experiment focuses on determining the crushing value of aggregate samples using the ACV test method. It is applicable to both coarse and fine aggregates commonly used in construction projects.
Objectives
-
To evaluate the aggregate samples for their crushing value.
- To assess the suitability of aggregates for various construction applications based on their crushing values.
Apparatus
- Sieves: 2.36mm, 10mm, and 14mm
- Cylinder: A cylindrical steel container with an internal diameter of 150mm and a depth of 130mm.
- Plunger: A steel plunger with a diameter of 150mm and a height of 100mm.
- Balance: A balance capable of weighing up to 10,000g.
- Oven: A laboratory oven capable of maintaining a temperature of 100 ± 5°C.
- Compression Testing Machine: A compression testing machine capable of applying a load of 40 tonnes at a uniform rate of 4 tonnes per minute.
Theory
The aggregate sample undergoes a specified load under standardized conditions, producing a percentage mass of fines, which is then calculated as a ratio of the weight of fines passing through specified sieves to the total weight of the sample to determine the crushing value of the aggregate. The lower the crushing value, the stronger the aggregate.
Procedure
- Collect a representative sample of the aggregate weighing at least 5,000g.
- Place the sample in the oven at a temperature of 100 ± 5°C for a period of 24 hours.
- After cooling, sieve the dried sample using the 2.36mm, 10mm, and 14mm sieves to obtain individual fractions.
- Weigh each fraction and record their respective weights.
- Assemble the cylindrical steel container on the base plate of the compression testing machine.
- Place the aggregate sample in the cylinder in three equal layers, compacting each layer with 25 strokes of the plunger.
- Apply a compressive load of 40 tonnes at a uniform rate of 4 tonnes per minute.
- Record the total weight of fines passing through the 2.36mm sieve and calculate the crushing value using the formula: Crushing Value = (Weight of Fines / Weight of Sample) × 100
Calculation
Crushing Value = (Weight of Fines / Weight of Sample) × 100
Note:
Weight of Fines is the sum of the weights of aggregates passing through the 2.36mm sieve.
Weight of Sample is the initial weight of the aggregate sample.
The experiment can be repeated with different aggregate samples to obtain multiple crushing values for analysis and comparison.
Conclusion
- It is essential to consider the specific requirements and intended use of aggregates when interpreting the crushing value results. Factors such as the type of construction, load-bearing capacity, and environmental conditions should be taken into account for appropriate aggregate selection.
- The experimental results can be used for quality control purposes, allowing engineers and construction professionals to make informed decisions regarding the selection and use of aggregates in specific applications. Aggregates with higher crushing values may be suitable for lower-stress applications, while those with lower crushing values can be used in high-stress scenarios.
- The crushing value is an important parameter that reflects the ability of aggregates to resist crushing under a compressive load. A lower crushing value indicates a stronger aggregate, suitable for use in construction applications that require high strength and durability.
- The aggregate samples tested in this experiment exhibited varying crushing values, suggesting differences in their quality and suitability for different construction purposes. Careful selection of aggregates based on their crushing values is crucial to ensure the desired performance and longevity of the constructed infrastructure.
- The experiment provided valuable information on the crushing value of the tested aggregates, enabling informed decision-making in the field of civil engineering. The results can contribute to the optimization of material selection, ensuring the construction of durable and resilient infrastructure. Further studies and comparisons with additional aggregate samples would enhance the understanding of aggregate properties and their impact on construction performance.
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