Quick answer: Concrete should be kept continuously moist for at least 7 days with ordinary Portland cement, and for 10 to 14 days in hot, dry or windy weather such as a Lahore summer. In summer, pour early in the morning or in the evening, keep materials cool and start curing as soon as the surface can take it. In the monsoon, protect fresh concrete from rain for the first few hours, avoid pouring in heavy rain and drain water from excavations.
Why Curing Matters
Cement needs water to hydrate and gain strength. If concrete dries out early, it can lose a significant part of its potential strength, develop surface cracks and become more permeable, which leads to leaks and rusting steel later. Curing is one of the cheapest ways to improve concrete quality.
Recommended Curing Periods
| Element | Normal weather | Hot, dry weather |
|---|---|---|
| Roof slabs | 7 days minimum | 10 - 14 days |
| Columns and beams | 7 days minimum | 10 - 14 days |
| Brick masonry | 7 days | 7 - 10 days |
| Plaster | 7 days | 7 - 10 days |
| Concrete with SRC, slag or blended cement | Longer curing, as advised by the engineer | |
Curing Methods
- Ponding: Small mortar bunds on the slab hold 1 to 2 inches of water. Very effective for slabs.
- Wet hessian or jute: Wet sacks wrapped around columns and beams, kept wet throughout the day.
- Plastic sheets: Cover wet concrete to stop evaporation, especially useful in windy weather.
- Water spraying: Frequent spraying of walls and plaster. Never let surfaces dry between sprays.
- Curing compounds: Sprayed membranes for surfaces that are hard to keep wet, where approved.
Summer Precautions (Hot Weather Concreting)
- Pour at the right time: Early morning or late evening, avoiding peak afternoon heat.
- Keep materials cool: Shade the crush and sand, and use cool water. Avoid concrete becoming very hot during placing.
- Wet the formwork and base before pouring so they do not absorb water from the concrete.
- Place and compact quickly: Hot weather shortens working time.
- Never add extra water to stiffening concrete; use an approved retarder or plasticizer if needed. See our mix ratio guide.
- Protect the surface immediately from sun and wind with sheets or wet hessian.
- Start curing early and keep it continuous, including at night.
Monsoon Precautions
- Check the forecast before major pours and keep plastic sheets ready.
- Avoid pouring in heavy rain: Rain on fresh concrete washes out cement and raises the water content.
- Drain excavations: Do not pour foundations into standing water.
- Protect stored cement on raised platforms under cover.
- Check sand moisture: Wet sand adds water to the mix, so reduce added water accordingly.
- Inspect scaffolding and shuttering after storms before restarting work.
- Protect fresh plaster from driving rain.
When Can Formwork Be Removed?
The structural engineer should set removal times. Commonly followed guidance for ordinary Portland cement in normal temperatures is:
| Formwork | Typical minimum time |
|---|---|
| Vertical sides of columns, walls and beams | 16 - 24 hours |
| Slab soffit (props left under) | 3 days |
| Props under slabs up to about 15 ft span | 7 days |
| Props under slabs over about 15 ft span | 14 days |
| Props under beams up to about 20 ft span | 14 days |
| Props under beams over about 20 ft span | 21 days |
Never load a new slab with bricks, cement or the next floor's materials before the engineer allows it.
Signs of Poor Curing
- Fine surface cracks (plastic shrinkage cracks) within hours of pouring
- Dusty, powdery surfaces
- Low cube or cylinder test results
- Early seepage through slabs
Read more about cracks and seepage and plan your schedule with our construction timeline guide.
Planet Builders follows written curing and formwork schedules on every grey structure project, supervised by our engineering team.
Frequently Asked Questions
How many days should a slab be cured?
At least 7 days with ordinary Portland cement, and 10 to 14 days in hot, dry weather.
Can concrete be poured in summer in Lahore?
Yes, with precautions: pour early morning or evening, keep materials cool, protect the surface and cure continuously.
Is it safe to pour concrete in the rain?
Light drizzle may be manageable with protection, but heavy rain damages fresh concrete. Postpone major pours if heavy rain is expected.
When can I remove slab props?
Commonly 7 days for slabs up to about 15 ft span and 14 days for longer spans, but always follow the engineer's instructions.
Want your structure built right in every season? Contact Planet Builders & Interiors.