---
title: "Cold weather concreting"
subject: "Concrete Technology and Masonry Structure"
chapter: 3
key: "semester_5/concrete_technology_and_masonry_structure:cold-weather-concreting"
source: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/cold-weather-concreting
site: BCT Engineering
---

# Cold weather concreting

Concrete Technology and Masonry Structure · Chapter 3: Mix design of concrete and property of green concrete

- Asked in: 2070 Chaitra, 4 marks
- Video: [Cold Weather Concreting - Durability of Concrete -  Advanced Concrete Technology](https://www.youtube.com/watch?v=WoHWmVEjkZo) — Ekeeda
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/cold-weather-concreting
- Whole chapter: https://www.bctengineer.com/md/semester_5/concrete_technology_and_masonry_structure/chapter-3

## Question

What are the effects of cold weather concreting? Explain the precautionary measures to take for concreting in cold weather.

## Short answer

Cold weather (below 5°C) delays setting, and freezing can permanently lose over 50% strength. Precautions: heat mixing water up to 60°C, ensure concrete temperature above 5°C at placing, use rapid-hardening cement, lower w/c, and accelerating admixtures. Insulate with blankets, keep concrete above 5°C for at least 48 hours, and protect for about 7 days.

## Answer

**Effects of cold weather (below about 5 °C)**
- Slower hydration, so setting and strength gain are delayed and the formwork must stay in place longer.
- If fresh concrete freezes before reaching about 3.5 MPa, the water turns to ice and expands by about 9%, causing a permanent loss of strength (up to 50% or more) and poor durability.
- Freeze-thaw damage of young concrete, and scaling of the surface.
- Thermal stress cracking from the temperature difference between the warm core and the cold surface.

**Precautions (IS 456 Cl. 14.1, which refers to IS 7861 Part 2; ACI 306)**
1. Heat the mixing water (up to about 60 °C) and, if needed, the aggregates; do not let cement come into contact with water hotter than about 60 °C (flash set). The concrete temperature at placing should be not less than 5 °C (IS 7861 Part 2), and 10 to 20 °C is recommended.
2. Use rapid-hardening cement, a higher cement content, a lower W/C, accelerating admixtures (non-chloride for RCC) and air-entraining agents.
3. Remove snow, ice and frost from forms, reinforcement and subgrade; never place concrete on frozen ground.
4. Cover with insulating blankets, polythene and straw, or use heated enclosures.
5. Keep the concrete above 5 °C for at least 48 hours and protect it for about 7 days; delay form stripping, and judge strength from test cubes cured under site conditions.
6. Avoid sudden cooling when the protection is removed.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. If fresh concrete freezes before gaining about 3.5 MPa, the main effect is:
   A. faster hydration and early high strength
   B. only a temporary delay that is fully recovered
   C. water turns to ice and expands about 9%, causing permanent strength loss
   D. reduced shrinkage and better durability
   Answer: C. Ice expansion disrupts the young paste, giving permanent loss of strength (up to 50% or more). (Key point: Effect of freezing)

2. Cold weather mainly affects hydration by:
   A. slowing it, so setting and strength gain are delayed
   B. speeding it, causing flash set
   C. stopping the need for curing
   D. raising the heat of hydration
   Answer: A. Low temperature slows hydration, so forms must stay longer. (Key point: Effect on hydration)

3. Why should mixing water not be heated above about 60 C?
   A. Hot water reduces the cement content
   B. Cement touching very hot water can flash set
   C. It increases the W/C required
   D. It causes freezing of aggregates
   Answer: B. Water hotter than about 60 C risks flash set when it meets cement. (Key point: Water temperature limit)

4. Which is a correct cold-weather precaution?
   A. Place concrete on frozen ground to save time
   B. Strip forms early to let heat escape
   C. Use calcium chloride accelerator freely in RCC
   D. Remove snow and frost from forms and subgrade, never place on frozen ground, and keep concrete above 5 C for at least 48 hours
   Answer: D. Frozen surfaces must be cleared and concrete protected; chloride accelerators are avoided for RCC. (Key point: Protection measures)

## Related in Concrete Technology and Masonry Structure

- [Hot weather concreting: effects, precautions](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Ahot-weather-effects-precautions) — Concrete Technology and Masonry Structure, chapter 3
- [Hot weather concreting precautions](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Ahot-weather-precautions) — Concrete Technology and Masonry Structure, chapter 3, asked 2×

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