The Sand Equivalent Test: Method and What the Result Means

Sand equivalent is one of the fastest ways to measure the cleanliness of fine aggregate. It needs no complicated equipment, which gives it a special place in the daily control of sites and asphalt plants.

What the test measures

Sand equivalent (ASTM D2419) shows the volumetric ratio of sand-like material to clay-like fines in the fraction passing the 4.75 mm sieve. A higher number means a cleaner material.

The method in plain terms

1. The sample goes into a graduated cylinder with a flocculating solution.
2. After soaking, the cylinder is shaken by the standard method to free the clay coating from the particles.
3. Solution is injected from the bottom of the cylinder, lifting the fines into suspension.
4. After settling, two levels are read: the top of the clay suspension and the top of the sand.

Calculating the result

Sand equivalent equals the sand reading divided by the clay reading, times 100. In a hypothetical example, with a sand reading of 3.2 and a clay reading of 4.6, the result is about 70.

Where the limit comes from

There is no single limit for sand equivalent. The specification for the use sets it; for road and asphalt materials in Iran, see Publications 101 and 234 and the project specification.

Limits of interpretation

• The test does not fully separate stone dust from active clay.
• For crushed sand, the methylene blue test gives a clearer picture of active clay.
• Its number does not replace the test for material finer than the 75 µm sieve (ASTM C117); the two complement each other.

See the role of this test in decisions in Aggregate washing and on the quality and standards page.