What additives and additives are added to concrete and why?

As you all probably know, concrete is made up of several basic components. These are cement, sand / gravel and water. But sometimes a solution with special properties is needed, so impurities are added to it. Which ones - I'll tell you today.

GOST 24211-2008 "Additives for concrete and mortar" separates all impurities and additives for concrete into varieties:

• Impurities that affect the properties of the concrete solution mixture:

- plasticizers

- regulators of the mobility of the solution without adding water

- stabilizers

- for gas formation and air entrainment

• Admixtures affecting the functionality of concrete:

- improving strength characteristics

- hardening regulators

- adding resistance to cold

- additional protection

- adding anti-corrosion effect

- reducing permeability

- expanding.

• Additives for special properties:

- anti-freezing

- hydrophobic

• Mineral supplements.

I'll tell you more about several of them.

Plasticizers. These additives make the concrete mix plastic, so the concrete fits better and fills chips, cracks, hard-to-reach places more easily. The presence of a plasticizer in the solution reduces the amount of water required by 10-20%, and reduces cement consumption by 10-15%, without reducing the strength and adhesive properties.

Air-entraining and gas-forming impurities. They have a disadvantage - they reduce the strength properties of concrete. Therefore, their amount in the concrete mix should be minimal. But you shouldn't avoid them. There must be air in the concrete. This will give it resistance to subzero temperatures, increase tensile strength and durability. At low temperatures, the water in the concrete freezes, begins to expand and "tear the concrete". To prevent this, use air entraining additives.

Gas-forming impurities are needed for internal partitions. The microporosity created by gas additives add heat-insulating properties to the concrete.

Hardening regulators. They are used to speed up and slow down the hardening of concrete. An increase in the speed of hardening is necessary in frost and low temperatures, because concrete in the cold cannot dry out. It is usually necessary to slow down the speed when moving concrete for a long time, or for pouring structures of a large area, which require uniform drying.

Strength additives. Plasticizers, stabilizers and reinforcing additives do an excellent job with this function. They make the mortar more plastic, increase its strength characteristics and the period of operation.

Water repellent additives. These include water-soluble silicones and siloxanes, silanes, and water-insoluble silicones. These additives are necessary to improve the water repellency of concrete, protecting it from moisture and extending its service life.

Thank youThank you for reading my article to the end!