In summer, the temperature is high and the drying is fast. The newly poured concrete may have an accelerated condensing speed and a decrease in strength. At this time, care should be taken when pouring, trimming and curing the concrete.
First, mixing and transportation:
When mixing, the measures should be taken to control the temperature rise of the crucible, and the additional water quantity should be controlled at one time to reduce the slump loss and reduce the plastic shrinkage cracking. The following measures can be taken during the mixing and transportation process.
1. Use water reducing agent or replace some cement with fly ash to reduce the amount of cement, and increase the aggregate particle size while the casting conditions allow.
2. If the transportation distance of the bismuth mixture is long, the setting time of the hydrazine can be controlled by a retarder, but it should be noted that the dosage of the retarder should be reasonable, especially for the large-scale slab floor project.
3. If you need a high slump bismuth mixture, use a superplasticizer. Some of the high- efficiency water reducing agent produced a slump of 2 h. The high-efficiency water reducing agent also reduces the friction between the aggregate particles during the mixing process and slows the heat accumulation in the mixing barrel.
4. In case of meeting the requirements of construction specifications, try to use slag Portland cement and fly ash Portland cement.
5. Sprinkle water into the aggregate to reduce the temperature of the aggregate; if it is sprayed with groundwater or well water, the cooling effect is better.
6. In the hot season or large volume concrete construction, cold water or ice cubes can be used instead of some mixing water.
7. For the long-distance transportation of sputum in the hot season, the delayed stirring of the mixer can be considered, so that the raft is still in agitating state when it arrives at the construction site.
8. It is recommended abroad to paint the outside of the drum of the mixer in white in the summer, so that the absorption of solar radiation by the drum is significantly reduced. In the summer, taking the transport distance of 1 h as an example, the temperature in the white mixing drum is at least 1 ° C lower than that in the conventional red mixing drum.
9. Construction organization design should be done to avoid pouring concrete at the highest temperature in the day. During the high temperature drying season, the evening pouring is relatively less affected by wind and temperature, and can be finally condensed near sunrise, while the relative humidity is high, so the possibility of early drying and cracking is minimal.
