IS 383:2016 — Aggregates for Concrete Explained

Aggregate is about 70% of concrete by volume, so its quality quietly decides the concrete's — and IS 383 is the code that sets what is fit to use. It covers the sand (fine aggregate) and the metal (coarse aggregate), their grading, and the limits on the rubbish that must not be in them.

The four grading zones of sand

IS 383 classifies fine aggregate into four grading zones, I (coarsest) to IV (finest), by how much passes each standard sieve:

Zone II sand is the general-purpose choice for concrete.
Zones I and III are usable within limits.
Zone IV is very fine and needs more water and cement for the same workability, so it is used with care.

Knowing the zone lets you compare and blend sands consistently instead of guessing by eye.

Coarse aggregate

For ordinary house RCC the nominal maximum size is usually 20 mm (it must be small enough to pass between the reinforcement and the cover); 40 mm is used for mass concrete and PCC where there is no congestion. IS 383 also sets the requirements for the shape and strength of the stone.

Deleterious materials — the limits that matter on site

IS 383 caps the harmful content — clay, silt, fine dust, organic matter — because these coat the aggregate and weaken the bond with the cement paste. The everyday site version of this is the silt check on sand: keep silt below about 8% (some specs 6%), tested with the simple jar test — fill a jar with sand and water, shake, let it settle, and read the silt layer as a percentage of the sand.

Two more field realities the code is really about:

Bulking of sand: damp sand's loose volume swells 20–30%. If you batch by volume without allowing for it, every mix is under-sanded (the brass and volume math).
Washing: dirty aggregate should be washed; the dust it carries is exactly what IS 383 limits.

Manufactured and recycled aggregate

The 2016 revision formally allows manufactured sand (M-sand) and, within limits, recycled concrete and mixed recycled aggregate for defined applications — recognising that natural river sand is a scarce resource and that crushed-rock sand, properly graded, performs well.

Frequently asked questions

What is IS 383:2016? The Indian Standard specification for coarse and fine aggregate for concrete — grading, quality, size and the limits on deleterious materials.

What are the four zones of sand in IS 383? Zone I (coarsest) to Zone IV (finest), by grading. Zone II is the usual choice for concrete; Zone IV is very fine and needs more water and cement.

What is the silt content limit for sand? Roughly under 8% (some specifications 6%) for concrete sand, checked on site with the jar test.

What is the maximum size of aggregate for house construction? Typically 20 mm nominal for RCC (small enough to pass the reinforcement), and 40 mm for PCC and mass concrete.

IS 383:2016 — Coarse and Fine Aggregate