As temperatures rise during summer, refractory concretes can exhibit significant changes in setting behavior — a phenomenon known as “quick setting.”
For example, a hydraulic refractory concrete installed at 20°C may begin to set after an hour and allow for formwork removal after 12 hours. However, under 37°C, the same concrete might begin setting in just 10 minutes — becoming rock-hard within 15 minutes, making proper placement nearly impossible. This abnormal behavior is caused by the accelerated hydration and crystallization of calcium aluminate cement, whose reaction intensifies with heat.
Phosphate-bonded concretes are also sensitive. Even at 20°C, they can reach 55°C during setting within 10–15 minutes. With higher ambient temperatures, the reaction speeds up so much that the concrete may harden inside the mixer.
To avoid these issues during hot weather, here are 5 key recommendations:
1. Store materials and liquids in the shade to minimize temperature increase.
2. Use chilled water (<20°C) when possible. For phosphate-bonded concretes, ice or coolers may be necessary.
3. Schedule casting during cooler hours — early morning or nighttime.
4. Have setting retarders on hand for hydraulic-bonded products.
5. Ensure mixers are clean and free from impurities that may accelerate setting and harm performance.
Summer heat demands special attention — proper planning ensures consistent results and prevents costly surprises on-site.