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Summer has arrived, and the process of pouring concrete must change with the hotter temperatures. The heat that comes with summer affects more than just the concrete workers themselves; heat also impacts the quality of your concrete.
Hot weather can have significant impacts to the long-term strength of your concrete. Yes, the initial strength will be stronger with faster than usual set times, but it does not give enough time for the crystals surrounding the aggregate to grow and reach the max strength. A rise of 10 degrees Celsius in temperature can cause a 10% loss in strength after 28 days.
Another impact of heat is that it causes the water to evaporate, thereby decreasing the slump and causing the concrete to become unworkable. This in turn typically leads to the addition of more water being added to the mix resulting in greater strength losses up to an additional 10%.
Concrete surface drying is another impact of the summer pours. The water evaporates and is sucked to the surface. The remaining water still rises but is left on the top later of the surface. This causes weakening of the top layer which results in the surface cracking, splitting and blistering.
To prevent these negative effects on your concrete, try these changes to ensure top quality concrete:
Simply protecting your pour from the sun is an effective way of limiting the evaporation and slowing the set time.
You can slow your set time by adding retarders to the concrete. Retarders slow the set time to allow concrete to receive an appropriate amount of time to complete the chemical reaction and maintain a higher slump.
When dealing with floor work and pad work, keeping your forms and ground wet with cold water can ensure that the bottom layer maintains hydration through the evaporation stage.
Using curing blankets can keep sunlight off your pour and control the evaporation. Curing compound is a good way of sealing the top of the pour to prevent water from escaping. Different types of compound will have different long-term reactions. Chlorinated rubber and wax concrete compounds eventually wear out over time, whereas some compounds will need to be washed off.
The mix is already being affected by the sun and heat; why hamper your summer pour abilities by allowing more time for the concrete to set in the delivery stage? Producing on site with a volumetric mixer or having a ready-mix plant nearby is especially important.
Summer concrete is a challenge but using these tips can ensure that your concrete strength is maintained. And most importantly, don’t forget to keep both your concrete and your bodies hydrated.