Reviewed by Er. Inderjit Sharma (Retd.), Punjab PWD
What are setting times? When water is added to cement, the paste slowly stiffens and hardens.
- Initial setting time: the time when the paste starts to lose its plasticity. Concrete must be mixed, transported, placed and compacted before this.
- Final setting time: the time when the paste has completely lost its plasticity and become hard enough to resist a light point load.
Both are measured with the Vicat apparatus, as per IS 4031 (Part 5).
Setting Time on a Timeline
Apparatus Required
Vicat apparatus
Frame with a sliding rod (300 g), a scale and three interchangeable attachments.
Setting needles
Square needle (1 mm) for initial set; needle with collar for final set.
Vicat mould
Split ring 40 mm deep, resting on a glass plate.
Balance (1 g)
Weighs cement and water.
Gauging trowel
Mixes the paste on a non-porous plate.
Measuring cylinder & stopwatch
Measure water; time everything from when water is added.
The Vicat Needles
Procedure
Step 1: Prepare the Paste
- First find the standard consistency (P) of the cement (IS 4031 Part 4).
- Weigh the cement and add water equal to 0.85 P (for example, 400 g cement with P = 30% → 0.85 × 0.30 × 400 = 102 ml).
- Start the stopwatch the moment water is added. Mix with the trowel; finish gauging in 3–5 minutes.
- Fill the Vicat mould on a glass plate, level the top, and keep it at 27 ± 2 °C and at least 90% humidity between readings.
Step 2: Initial Setting Time
- Fit the square needle (1 mm × 1 mm). Lower it gently until it touches the paste, then release it quickly.
- At first the needle goes right to the bottom. Repeat every few minutes at a fresh spot (away from the edge and earlier holes).
- The initial setting time is reached when the needle stops 5 ± 0.5 mm above the bottom of the mould. Note the time from when water was added.
Step 3: Final Setting Time
- Replace the needle with the final setting needle (needle with a round metal collar).
- Lower and release it gently on the paste surface at intervals.
- The final setting time is reached when the needle makes a mark but the collar does not. Note the time from when water was added.
Requirements
| Cement | Initial setting time | Final setting time |
|---|---|---|
| OPC (33, 43, 53), PPC, PSC | not less than 30 minutes | not more than 600 minutes (10 hours) |
| Low heat Portland cement | not less than 60 minutes | not more than 600 minutes |
As per IS 269, IS 1489, IS 455 and IS 12600. Follow the cement standard and your contract specification.
Try It: Setting Time Calculator
Enter the clock times. The values filled in are a worked example.
Water for the paste
Precautions
⏱️ Time from water
All times count from the moment water touches the cement. Start the stopwatch then.
📍 New spot each time
Never drop the needle in an old hole or near the edge of the mould; it gives a false reading.
🌡️ Keep it moist and at 27 °C
Store the mould in a moist cabinet (90% humidity or more) between readings; drying makes the paste set faster.
🧽 Clean, straight needle
Wipe the needle after each reading and use only a straight, undamaged needle.
Practical Tips for Site Engineers
- Place before initial set: mixing, transport, placing and compaction must finish well before the initial setting time. Never re-temper (add water and remix) concrete that has started to stiffen.
- Hot weather speeds it up: setting can happen much faster in summer. Mix and place quickly, use cool water, shade aggregates, pour in the cooler hours, and use a retarder if specified.
- Cold weather slows it down: formwork removal and finishing take longer; plan the schedule accordingly.
- Ready-mix concrete: check the batching time on the delivery ticket and reject loads that exceed the time limit in your specification (commonly about 90–120 minutes without retarders).
- Don’t disturb after initial set: avoid vibrating, walking on or moving fresh concrete between initial and final set; it can crack and weaken it.
- Odd behaviour = test the cement: very quick stiffening (false set or flash set) or concrete that stays soft for too long means you should test the cement’s setting time before using more of that lot.
- Old or lumpy cement: moisture-affected cement often sets abnormally. Test it before use.
Key Takeaways
- Initial set = paste starts losing plasticity; final set = paste fully hard.
- Use water = 0.85 P; time everything from when water is added; keep at 27 °C and 90%+ humidity.
- Initial set: the square needle stops 5 ± 0.5 mm above the bottom. Final set: the needle marks the surface but the collar does not.
- Limits: initial at least 30 min (60 min for low heat cement); final at most 600 min.
- On site: place and compact concrete before the initial set; watch hot weather and ready-mix delivery times.
References: IS 4031 (Part 5): Determination of Initial and Final Setting Times; IS 4031 (Part 4): Standard Consistency; IS 5513: Vicat Apparatus; IS 269: Ordinary Portland Cement; IS 1489: Portland Pozzolana Cement; IS 4926: Ready-Mixed Concrete.