Hot weather concreting can bring a large number of issues that could be detrimental to the construction of a building, we have provided a list of both challenges and precautions for you to try and combat this.
The Challenges Of Hot Weather Concreting
Concreting in hot weather comes along with many challenges which can all greatly diminish the quality of the concrete. The main challenges that can occur are:
Consistence, otherwise known as accelerated slump loss leading to the addition of water on the job-site. The slump/flow/slump flow of concrete reduces more rapidly. Adding water to improve the consistency shall decrease the concrete’s compressive strength, potentially increase permeability and ultimately affect the durability of the structure.
The setting time when hot weather concreting also finds itself to be a challenge. As concrete temperatures increase the setting time is reduced and thus the time to place, compact and finish the concrete is reduced. Consequently increased setting time can lead to strength loss, which is a major health and safety issue. To try and combat the fast setting time of the concrete often people will simply try to work faster, which in extremely hot weather can prove to be difficult and also dangerous.
Thermal cracking occurs due to excessive temperature differences within a concrete structure or its surroundings when it is first placed and the heat of hydration raises the temperature of the interior of the concrete. Changes in temperature of the concrete may also result in cracking particularly where concrete is placed on a hot day followed by a cool night.
The surface finish of the concrete may also be affected when concreting in hot weather. This is due to the concrete seeming dry to the naked eye when in fact it is not. Consequently, this may lead to a premature finish being applied on top of concrete that is not completely dry – trapping an amount of bleed water, this bleed water may result in debonding of the top surface and subsequent flaking/de-lamination.
9 Precautions To Take When Hot Weather Concreting
- Prior to concrete placement, think about moisten subgrade, steel reinforcement, and formwork.
- Erect temporary windbreaks to limit wind velocities and sunshades to reduce concrete surface temperatures, this will also help to eliminate the surface finish debonding of the top surface and subsequent flaking/de-lamination.
- Cool aggregates and mixing water added to the concrete mixture to reduce its initial temperature. The effect of hot cement on concrete temperature is only minimal.
- Use a concrete consistency that allows rapid placement and consolidation, to prevent any issues with the durability of your structure.
- Protect the concrete surface during placement with plastic sheeting or evaporation retarders to maintain the initial moisture in the concrete mixture.
- Provide sufficient labour to minimize the time required to place and finish the concrete, as hot weather conditions substantially shorted the times to initial and final set.
- Consider fogging the area above the concrete placement to raise the relative humidity and satisfy moisture demand of the ambient air.
- Provide appropriate curing methods as soon as possible after the concrete finishing processes have been completed.
- In extreme conditions consider adjusting the time of concrete placement to take advantage of cooler temperatures, such as early morning or night time placement.
We hope that you take all of these into consideration when concreting during hot months. To learn more about Al Manaratain concrete products, take a look at our website.