TYPES OF ADMIXTURE | FUNCTION OF ADMIXTURE
What are Admixture?
Admixtures are artificial or natural ingredients that are added to concrete in addition to cement, water, and aggregate to improve particular attributes during the casting, setting, or service stage.
It may be separated into two groups in order to improve the quality of the concrete:
As previously stated, admixtures are used to change the characteristics of concrete. The main functions and advantages of using admixtures are discussed further below.
- To increase durability by air entrainment
- To provide water resistant / waterproofing properties
- To reduce the amount of water required
- To speed up the setting and hardening process, resulting in high early strength.
- To aid in the healing process
- To improve the workability of new concrete
- To retard setting
- Boosting abrasion resistance (hardness).
- To account for or reduce shrinkage during the hardening and setting processes.
- Generate concrete expansion and steel prestressing automatically
- Aerating mortar or concrete to make a lighter product
- Concrete coloring
- To reduce the consequences of a chemical reaction.
- To reduce bleeding
- Reduced heat evaporation
- To induce the cement particles to disperse when combined with water
TYPES OF ADMIXTURE
Accelerating Admixture – These types of admixture can be used to improve the pace of stiffening or setting of the concrete, as well as the rate of hardening and early strength acquisition, allowing for quicker formwork striking and demolding.
Air-entraining Admixture – It is a type of admixture that causes the development of a system of microscopic air bubbles in cement paste during mixing, usually to increase its resistance to freezing and thawing and to improve workability.
Anti Washout Admixture– In concrete, an anti-wash admixture is employed, especially in underwater concrete constructions. It essentially protects the concrete mix from being washed underwater under pressure. As a consequence, the cohesion of concrete has improved. Natural or synthetic rubbers, cellulose-based thickeners, and other ingredients are used to make this sort of combination.
Bonding admixture– In order to form a connection between old and new concrete surfaces, Bonding Admixture is utilized.
Coloring Admixture– As the name suggests, coloring mixture is a combination of pigments that give the final concrete its color. The concrete’s strength should not be compromised by the colorant combinations.
Corrosion Preventing Admixtures– Steel corrosion in reinforced concrete structures is widespread, and it is particularly severe when the structure is exposed to salty water, industrial gases, chlorides, and other corrosive substances. Corrosion-preventing admixtures are used to prevent or slow down the corrosion process. Sodium benzoate, sodium nitrate, sodium nitrite, and other corrosion-preventing admixtures are commonly employed in reinforced concrete.
Damp-Proofing Admixtures– Concrete structures are impervious to water, and dampness is prevented by using damp-proofing or water-proofing admixtures to avoid dampness on the concrete surface. Their water-proofing properties also make them useful as accelerators during the early stages of concrete hardening. Damp-proofing admixtures are offered in liquid, powder, and paste forms, among other formats. They are chemically active pore fillers such as aluminum sulfate and zinc sulfate. They also contain aluminum chloride, calcium chloride, silicate of soda, and so on.
Grouting Admixture – Grout additions are additives that are added to grout ingredients to improve the characteristics of the grout. Sometimes rapid grouting is required, while other times gradual grouting is required to spread into deep cracks or fissures.
Moisture Proof Admixture -Waterproofing is a term that refers to the ability to withstand moisture. Admixture is used to make the concrete structure impermeable to water and to prevent moisture from forming on the surface of the concrete.
Plasticizers Admixture -The combination of organic compounds or organic and inorganic substances that results in a lower water content for a given workability or a greater workability for the same water content.
Retarding Admixture– Retarding admixtures are used to decelerate the setting of concrete, which is accelerated by hot weather. The hardening process can be accelerated by high temperatures, making placement and finishing more difficult. While delaying the first batch of concrete, retarders make the concrete workable for installation. The majority of retarders are also water reducers and may enable some air into the concrete.
Water-reducing Admixture– These types of admixture lower the amount of water required for a concrete mixture by 5 to 10%. The water-cement ratio in treated concrete may be lower than in untreated concrete. This means that stronger concrete may be made without adding more cement. Recent developments in admixture technology have resulted in the creation of mid-range water reducers with at least an 8% reduction in water content.