Aggregate Crushing Value Test: Principles, Procedure, and Significance (Based on BS 812-110)
The aggregate crushing value (ACV) test is a standardized method used to assess the resistance of coarse aggregates to crushing under a gradually applied compressive load. This test is essential in evaluating the suitability of aggregates for use in construction, particularly in road pavements and concrete structures where mechanical strength is critical. The procedure is detailed in British Standard BS 812-110:1990, which outlines the methodology for determining the aggregate crushing value of coarse aggregates.
Purpose and Significance
The primary objective of the ACV test is to provide a relative measure of an aggregate's ability to withstand crushing forces. Aggregates with lower crushing values are preferred for high-stress applications such as road bases, sub-bases, and wearing courses, as they are less likely to degrade under traffic loads. According to BS 812-110, the test simulates the stresses that aggregates may experience during service, helping engineers predict long-term performance and durability.
Test Apparatus
The equipment required for the test includes:
- A steel cylinder with a plunger and base plate
- A compression testing machine capable of applying a load up to 400 kN at a uniform rate
- IS sieves of sizes 12.5 mm, 10 mm, and 2.36 mm
- A tamping rod
- A balance accurate to 0.1 g
- A cylindrical measure for sample preparation
Sample Preparation
The test is conducted on aggregates that pass the 12.5 mm sieve and are retained on the 10 mm sieve. The sample is oven-dried at 105°C ± 5°C for 4 hours and cooled to room temperature. Approximately 6.5 kg of aggregate is used to fill the cylindrical measure in three equal layers, each compacted with 25 strokes of the tamping rod. The surface is leveled, and the plunger is placed on top.
Test Procedure
The prepared cylinder is placed in the compression testing machine and loaded at a rate of 4 kN/s until a total load of 400 kN is reached. The load is then released, and the crushed material is removed. The material is sieved through a 2.36 mm sieve, and the fraction passing this sieve is weighed.
The aggregate crushing value is calculated using the formula:
ACV = (Weight of fines passing 2.36 mm sieve / Total weight of sample) × 100
Reporting and Interpretation
Results are reported to the nearest whole number. According to BS 812-110, the ACV should be determined as the mean of two tests. If the individual results differ by more than 0.07 times the mean value, the test should be repeated on two additional specimens, and the median of the four results reported..jpg)
Interpretation guidelines suggest: .jpg)
- ACV < 10%: Exceptionally strong aggregates
- 10–20%: Strong aggregates
- 20–30%: Satisfactory for base courses
-
30%: Weak aggregates, generally unsuitable for high-stress applications
Applications and Limitations
The ACV test is widely used in quality control for road construction and concrete production. It is particularly relevant in specifications set by highway authorities in the UK and other countries following British standards. However, it is a relative measure and does not fully represent the aggregate's performance under impact or abrasion, which are assessed through other tests like the aggregate impact value (AIV) and Los Angeles abrasion test.
Conclusion
The aggregate crushing value test, as defined in BS 812-110, provides a reliable and standardized method for evaluating the strength of coarse aggregates. Its consistent application supports the selection of durable materials in civil engineering projects, contributing to the long-term integrity of infrastructure.
References
- British Standards Institution (BSI). (1990). BS 812-110:1990 Testing aggregates — Method for determination of aggregate crushing value. London: BSI.
- Neville, A. M., & Brooks, J. J. (2010). Concrete Technology (2nd ed.). Pearson Education.
- Ministry of Housing, Communities & Local Government (UK). Design Manual for Roads and Bridges (DMRB), HD 27/07 – Aggregates for Highway Works.