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

# Hot weather concreting: effects, precautions

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

- Asked in: 2071 Chaitra, 4 marks
- Video: [Hot Weather Concreting Precautions & Effects | Concrete Works | Concrete in Hot Weather? ~CivilWork](https://www.youtube.com/watch?v=N5SFT9K0Oh8) — Civil Work
- 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/hot-weather-effects-precautions
- Whole chapter: https://www.bctengineer.com/md/semester_5/concrete_technology_and_masonry_structure/chapter-3

## Question

What are the effects of hot weather on concreting? Explain the precautionary measures to be taken for concreting in hot weather.

## Short answer

Hot weather (above 30-35°C) causes rapid setting, slump loss, plastic shrinkage, lower long-term strength. Precautions: keep concrete temperature below 40°C by cooling materials, use retarders, place in cooler hours, protect with shades/fog sprays, and start moist curing immediately for at least 10 days.

## Answer

**Effects of hot weather (above about 30 to 35 °C, or low humidity and wind) on concrete**
- Faster setting and loss of slump, so more water tends to be added (higher W/C).
- Rapid evaporation, causing plastic shrinkage cracks.
- Higher early strength but lower 28-day and long-term strength.
- Difficulty in placing and finishing, and a risk of cold joints.
- More thermal cracking and drying shrinkage, higher permeability, and difficulty in controlling air entrainment.

**Precautions (IS 456 Cl. 14.1, which refers to IS 7861 Part 1; ACI 305)**
1. Keep the concrete temperature at placing below 40 °C (IS 7861 Part 1 limit). Shade aggregate stockpiles, paint tanks and pipes white, sprinkle water on aggregates, and use chilled water or crushed ice as part of the mixing water.
2. Use low-heat cement or fly ash blends; use retarding or water-reducing admixtures (not extra water).
3. Reduce transit time; mix, transport and place quickly; schedule casting in the early morning, evening or night.
4. Dampen the subgrade and formwork before casting; keep forms shaded.
5. Use windbreaks, sunshades, fog sprays or evaporation retardants to prevent plastic shrinkage.
6. Start curing immediately: wet hessian, ponding, continuous spraying, or a membrane curing compound; cure for at least 10 days (IS 456, Cl. 13.5.1).
7. Place smaller lifts and provide enough joints.

## Check yourself

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

1. In hot weather concrete shows
   A. higher early strength but lower 28-day strength
   B. lower early and higher later strength
   C. same strength
   D. slower setting
   Answer: A. Fast hydration gives lower later strength. (Key point: Effect on strength)

2. Rapid slump loss tempts workers to add water, which
   A. lowers w/c
   B. raises w/c
   C. raises strength
   D. has no effect
   Answer: B. Higher w/c lowers strength. (Key point: Slump loss)

3. IS 456 limits concrete temperature at placing to below
   A. 20 °C
   B. 60 °C
   C. 40 °C
   D. 30 °C
   Answer: C. Keep below 40 °C. (Key point: Temperature limit)

4. Curing in hot weather should start immediately and last at least
   A. 1 day
   B. 3 days
   C. 28 days
   D. 10 days
   Answer: D. IS 456 cl. 13.5.1 says 10 days. (Key point: Curing)

## Related in Concrete Technology and Masonry Structure

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