Higher temperatures cause a faster rate of water evaporation and cement hydration, thereby stiffening concrete earlier and increasing the risk of plastic cracking occurring.

Precautions

• If possible, sprinkle cool water on forms, steel and subgrade before placing
• Schedule mixer trucks to avoid waiting time
• Organise the job in advance, quickly place the concrete, and have sufficient workers to avoid delays
• After pouring, protect exposed surfaces from drying out through wind breaks, sunshades, fog sprays and approved curing membranes
• After finishing, consider a curing membrane, plastic sheeting or water sprays and strength development
• Use retarding admixtures to extend setting times
• Consider early morning or evening placement

Admixtures for Hot Weather

The laying of concrete in hot weather places extra demands on the concrete worker. The ideal conditions for concrete curing are between 10-30 C. The addition of extra heat and/or wind can have a detrimental effect on the finished product because of rapid moisture loss. Concrete develops its properties of durability, wear resistance, permeability and strength over time. To develop these qualities, the hydration must be prolonged. Prolonged hydration requires adequate moisture as well as an even temperature range. The excessive loss of moisture can cause shrinkage cracking. These problems can be controlled through the use of Admixtures.

Retarders

These are designed to retard setting times so that the concrete worker has enough time to finish the surface of the concrete. It is also useful for maintaining concrete slump during long haul times to construction sites.   Retarders temporarily stop the chemical action of hydration but after the planned delay hardening develops at an accelerated rate.

Allied Concrete staff are more than happy to help you with any problems or enquiries.

For more information or assistance, please don’t hesitate to call. Your call will be automatically connected to our nearest plant. (Calls from mobile phones will be directed for Auckland or Christchurch.)

DISCLAIMER: Allied Concrete has endeavoured to present the best possible information. However we accept no responsibility for the application of the principles discussed.