Post Date: 6,Jun,2022

At first, admixture was used only to save cement. With the development of construction technology, admixture has become the main measure to improve concrete performance.

Thanks to superplasticizers, high-flow concrete, self-compacting concrete, high-strength concrete are used; thanks to thickeners, the properties of underwater concrete are improved: thanks to retarders, the setting time of cement is prolonged , it is possible to reduce the slump loss and prolong the construction operation time: due to the antifreeze, the freezing point of the solution can be lowered, or the deformation of the ice crystal structure will not cause freezing damage. It is only possible to carry out construction under negative temperature.

In general, admixtures have the following effects in improving the properties of concrete:

 1. It can reduce the water consumption of concrete. Or increase the fluidity of the concrete without increasing the amount of water.

2. The setting time of concrete can be adjusted.

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

4. The slump loss can be reduced. Increase the pumpability of pumped concrete.

5. Shrinkage can be reduced. Adding a bulking agent can also compensate for shrinkage.

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

7. Improve the early strength of concrete. Prevent freezing under negative temperature.

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

9. Control the alkali-aggregate reaction. Prevent steel corrosion and reduce chloride ion diffusion.

10. Made of concrete with other special properties.

11. Reduce the viscosity coefficient of concrete, etc.

 After adding admixtures to concrete, due to different varieties, the effects are also different, most of which are physical effects, such as adsorption on the surface of cement particles to form an adsorption film, which changes the potential and produces different suction or repulsion; Destroy the flocculation structure, improve the stability of the cement diffusion system, and improve the conditions of cement hydration: some can form a macromolecular structure and change the adsorption state on the surface of the cement particles; some can reduce the surface tension and surface energy of water, etc.: and A few directly participate in chemical reactions and generate new compounds with cement.

Because the admixture can effectively improve the performance of concrete, and has good economic benefits. It has been widely used in many countries and has become an indispensable material in concrete. Especially the use of high potency reducers. The cement particles can be fully dispersed, the water consumption is greatly reduced, and the cement potential is fully utilized. As a result, the cement stone is relatively dense, and the pore structure and the microstructure of the interface area are well improved, so that the physical and mechanical properties of concrete have been greatly improved, whether it is water impermeability, or chloride ion diffusion, carbonization, and sulfate corrosion resistance. . As well as impact resistance, wear resistance and other aspects are better than concrete without admixtures, not only improve the strength, improve workability. It can also improve the durability of concrete. It is only possible to formulate high-performance concrete with high workability, high strength and high durability by mixing superplasticizers.