In the Saudi summer, high temperatures, low humidity and sometimes strong winds all speed up the loss of water from concrete. If the pour is not managed well, quality drops even when the mix itself is correctly designed.
What does heat do to concrete?
- Rapid loss of workability (slump), which sometimes tempts crews to add water that is not allowed.
- Faster setting and harder finishing.
- Plastic shrinkage cracks on the surface from rapid evaporation.
- Lower long-term strength if curing is not adequate.
Measures that limit the effect
- Cooling the mix ingredients, for example chilled water or crushed ice in place of part of the mixing water.
- Pouring at cooler times, such as early morning or at night.
- Cutting transport and waiting times, and using set retarders where needed within the approved design.
- Dampening formwork and subgrade before pouring, and shielding the surface from sun and wind.
- Starting moist curing as soon as finishing ends and keeping it up for the required period.
The role of site testing
Concrete temperature is measured on arrival and compared with the limit in the project specification, the slump test confirms workability, and cubes are taken and stored in suitable conditions; cubes left in the sun give results that do not represent the actual concrete.
The photo shows a digital thermometer on the surface of fresh concrete while one of our pours was being monitored.