Mixing in hot weather, how heat affects cement and concrete

How to mix concrete in hot weather: practical tips for builders

As summer temperatures rise, working with concrete becomes more challenging. If you’ve ever tried mixing in the heat, you’ll know how quickly things can start to go wrong.

Hot weather affects both the mixing and curing process, leading to potential issues if you're not prepared. Here’s what you need to know when working on site during hot conditions.

When it’s hot, two things happen fast

Water evaporates quicker and cement hydrates faster. This combination means you have much less time to work with your mix. The water that normally helps keep your concrete workable is lost quickly through evaporation, while the accelerated hydration speeds up setting time.

The result is reduced workability, a higher risk of surface cracks, and potential long-term weaknesses in the finished slab.

Hot conditions shorten the time you have to place, compact, and finish the mix before it starts setting.

Rapid drying can cause cracks to form on the surface even before the concrete has fully set. The mix can stiffen much faster than expected, making it harder to achieve the right consistency.

If water evaporates too quickly, you risk poor curing and a weaker surface finish that may not last.

There are some simple, effective ways to keep control of your mix in high temperatures. Start with cold water, or even add ice to the mix, to slow down the hydration process and give you more working time.

Keep the time between adding water and pouring the mix as short as possible to minimise evaporation losses.

If you can, schedule pours for early morning or late afternoon, avoiding the hottest period between 11 am and 3 pm.

Keep your cement bags, water, and equipment shaded before mixing to prevent them absorbing unnecessary heat.

Use wet curing methods or curing compounds to keep moisture in the slab and prevent rapid surface drying. Admixtures can be added to slow setting time and improve workability in hot conditions. Consider reducing joint sizes to help manage shrinkage cracks.

Finally, having extra hands on site means you can place and finish the concrete faster before it sets.

If you're using a traditional bucket and hose setup, you're already losing time before you start. Our CemixFlo Quick Connect Water Pipe helps you get the perfect amount of water into your mixer quickly and consistently, saving you precious minutes, especially when every second counts on hot days.

Concrete can be tricky in hot weather, but with a few adjustments and the right tools, you can keep your mix under control and your finished job looking spot on.