What role do concrete admixtures play, and can they be used without them?

Concrete admixtures include:

1. Admixtures that improve the performance of concrete mixtures and workability, including various water reducing agents, air entraining agents and pumping agents;

2. Admixtures that adjust the setting time and hardening performance of concrete, including retarder, early strength agent, accelerator, etc.;

3. Admixtures that improve the durability of concrete, including air-entraining agents , waterproofing agents and rust inhibitors, etc.;

4. Admixtures that improve other properties of concrete, including air-entraining agents, expansion agents, antifreeze agents, colorants, waterproofing agents and pumping agents, etc.

Admixtures have the following effects in improving the performance of concrete:

1. They can reduce the water consumption of concrete. Or they can increase the fluidity of concrete without increasing water consumption.

2. The setting time of concrete can be adjusted.

3. Reduce bleeding and segregation. Improve workability and water elution resistance.

4. It can reduce slump loss and increase the pumpability of pumped concrete.

5. It can reduce shrinkage. Adding expansion agent can also compensate for shrinkage.

6. Delay the initial hydration heat of concrete. Reduce the temperature rise rate of large-volume concrete and reduce the occurrence of cracks.

7. Improve the early strength of concrete and prevent freezing at negative temperatures.

8. Improve strength, increase frost resistance, impermeability, wear resistance and corrosion resistance.

9. Control the alkali-aggregate reaction. Prevent the corrosion of steel bars and reduce the diffusion of chloride ions.

10. Make concrete with other special properties. </p