as1141 21 aggregate crushing value

Determination of Aggregate Crushing Value (ACV) as per IS 1141:21

The Aggregate Crushing Value (ACV) test is a fundamental assessment in civil engineering to evaluate the strength of coarse aggregates used in road construction and other structural applications. The test is conducted as per the Indian Standard IS 1141:21, which specifies the procedure for determining the resistance of aggregates to crushing under a gradually applied compressive load.

Principle of the Test
The ACV test measures the percentage of fines produced when a specified mass of aggregate is subjected to a standardized crushing load. A lower ACV indicates stronger aggregates, which are more suitable for high-stress applications like pavement layers. The test involves compacting a sample of aggregates in a cylindrical mold and applying a compressive force of 40 tonnes over 10 minutes. The crushed material is then sieved, and the percentage passing through a 2.36 mm sieve is calculated as the ACV.

Apparatus Required
1. Compression Testing Machine: Capable of applying a load of 40 tonnes at a uniform rate.
2. Cylindrical Steel Mold: Measuring 150 mm in diameter and 130 mm in height, with a base plate and plunger.
3. Balance: Accurate to 0.1 g for weighing the sample.
4. Sieves: 12.5 mm, 10 mm, and 2.36 mm sieves for grading and analysis.
5. Tamping Rod: A straight metal rod with a rounded end for compacting the aggregate sample.

Procedure Overview
1. Sample Preparation: Dry the aggregate sample and sieve it to obtain particles passing through 12.5 mm and retained on 10 mm sieves.
2. Filling the Mold: Fill the cylindrical mold in three layers, tamping each layer with 25 strokes for uniform compaction.
3. Application of Load: Place the mold in the compression machine and apply a total load of 40 tonnes over 10 minutes at a steady rate.
4. Sieving and Calculation: Remove the crushed aggregate, sieve it through a 2.36 mm sieve, and weigh the material passing through it to determine the ACV percentage using the formula:

\[
\text{ACV} = \left( \frac{\text{Weight of material passing through } 2.36 \text{mm sieve}}{\text{Total