IS 4031 Part 9 : 1988Methods of Physical Tests for Hydraulic Cement - Part 9: Determination of drying shrinkage

IS 4031 Part 9:1988 is the method for determining the drying shrinkage of hydraulic cement mortar — how much a standard mortar specimen contracts as it loses moisture. It characterises a cement's contribution to shrinkage cracking, the most common non-structural defect in slabs, screeds, plaster and walls.

It sits in the cement-testing / dimensional-stability stack:

• IS 4031 Part 1 — physical tests for hydraulic cement (drying shrinkage among them) · IS 9459 — length-change comparator (the apparatus that measures it)
• IS 456 — concrete (cracking, joints) · IS 383 — aggregate (the bigger shrinkage driver in concrete) · IS 269 — OPC

Drying shrinkage in concrete is driven by water/paste content and aggregate, but the *cement itself* contributes, and cements differ. This test isolates that contribution on a standard mortar measured over a drying schedule with a length comparator:

• A standard mortar prism with gauge studs, length measured over time against an invar reference bar → shrinkage strain (microstrain) vs time
• A cement with high drying shrinkage raises the cracking risk of slabs/screeds/plaster made with it, all else equal
• It is one input among several — in real concrete, aggregate type/stiffness, total water and paste volume, restraint and joint spacing usually dominate — but a high-shrinkage cement is an avoidable amplifier

The engineering point: shrinkage is decoupled from strength — a strong cement can be a high-shrinkage one — and this test lets you compare cements on the property that drives the endemic cracking complaint, rather than discovering it after the slab maps and cracks.

Scenario: crack-sensitive work (large slabs, screeds, architectural plaster) with a history of shrinkage cracking.

Step 1 — compare cements: run the IS 4031 Part 9 drying-shrinkage test (via the IS 9459 comparator) on candidate cements → shrinkage-strain curves.

Step 2 — prefer low-shrinkage cement: all else equal, choose the lower-shrinkage cement for crack-sensitive work — an avoidable amplifier removed.

Step 3 — fix the bigger drivers too: low water/paste content, a stiff low-shrinkage aggregate, and detail joint spacing/reinforcement to the measured shrinkage (IS 456) — the cement is one lever among several.

Step 4 — cure well: proper moist curing significantly reduces early shrinkage cracking.

The test makes cement shrinkage a *selectable* variable instead of a post-crack surprise; combined with controlling water/paste, aggregate and joints, it designs out the endemic map/restraint cracking.

1. Ignoring shrinkage because strength is fine. Shrinkage is decoupled from strength — a strong cement can be high-shrinkage.

2. Treating the cement as the only lever. Aggregate, water/paste, restraint and joint spacing usually dominate concrete shrinkage — the cement is an amplifier, not the whole story.

3. No reference-bar zeroing. Skipping the invar reference (IS 9459) lets instrument/temperature drift masquerade as shrinkage.

4. Inconsistent drying regime. Length change depends on the conditioning schedule — comparisons valid only at the same regime.

5. Not using the result in joint design. Measured shrinkage should inform joint spacing/reinforcement, not just sit in a report.

• IS 4031 Part 1 — physical tests for hydraulic cement · IS 9459 — length-change comparator (the apparatus)
• IS 456 — concrete (cracking, crack-width, joints) · IS 383 — aggregate (dominant concrete-shrinkage driver)
• IS 269 — OPC · IS 10262 — mix design (low-water/paste, low-shrinkage)
• IS 3085 — permeability (shrinkage cracks compromise it)

IS 4031 Part 9 is reaffirmed and addresses the single most common concrete complaint in buildings — shrinkage cracking — at the cement-selection stage. The lesson it reinforces: shrinkage is independent of strength, so a strong cement is not necessarily a low-cracking one, and cement shrinkage is a *selectable* input rather than an act of fate. In real concrete the dominant levers are water/paste content, aggregate and restraint/joint spacing, so this test is best used to remove the cement as an *avoidable amplifier* in crack-sensitive work — choose the lower-shrinkage cement, then control water/paste, pick a stiff aggregate, detail joints to the measured shrinkage (IS 9459/IS 456) and cure well. Used that way the endemic map-and-restraint cracking becomes largely a designed-out problem instead of a recurring post-pour dispute.