It is well known that in the construction industry, concrete admixtures are added reasonably based on different floor materials, weather conditions and project locations, and reasonable communication is done with the mixing station. It is not appropriate to force the mixing station to make proportions according to the requirements of the construction unit. It should still be I believe in the professional opinions of the laboratory. If there is a quality accident in the concrete, the construction unit will bear a lot of responsibility.
Generally speaking, the addition of admixtures is the job of the mixing station. Mixing stations will be added as appropriate. There is no need to consider the construction site, and no additives can be added by yourself during pouring. A small amount of rough stone can be added on site. It can play a very good role in reducing and preventing the occurrence of stress cracks.
It doesn’t matter if the slump is larger. As long as the concrete proportion is correct and there is no segregation during on-site construction, the strength requirements will basically be met, because the grade will be increased for insurance when making the proportion. The water-cement ratio of concrete is an important indicator for controlling workability. If the water-cement ratio is too large, the fluidity and workability will be good, but the strength will easily fail to meet the requirements; if the water-cement ratio is too small, the workability will be poor and construction will be inconvenient
The construction unit shall do a good job in testing the concrete slump and sampling, and do a good job in physical maintenance. In case of concrete quality problems, it will cooperate with relevant departments to investigate and collect evidence in a timely manner, and reasonably investigate the responsibility of the mixing station
For the construction of large-volume concrete, the following measures should be taken according to the characteristics of the concrete:
1. If the design permits, the 60-d strength of concrete is used as the design strength;
2. Adopt Low-heat or medium-heat cement is mixed with admixtures such as fly ash and finely ground slag powder;
3. Mixed with concrete admixtures such as water reducing agent, retarder, and expansion agent;
4 During construction in hot seasons, cooling measures such as lowering the temperature of raw materials and reducing the absorption of external heat during concrete transportation shall be adopted;
5 Pre-embedded pipes inside the concrete for water-cooling and heat dissipation;
6. Use thermal insulation and moisturizing care. The difference between the concrete core temperature and the surface temperature should not be greater than 25°C, and the difference between the concrete surface temperature and the atmospheric temperature should not be greater than 25°C. The curing time should not be less than 14 days.
It can be seen that adding concrete admixtures can reduce the heat of cement hydration; delay the initial setting time of concrete; on the premise of ensuring the strength and slump requirements of concrete, the content of admixtures and aggregates should be increased , to reduce the cement dosage of single concrete; to prevent various cracks in concrete.
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