To increase the pumpability of concrete, any additive that makes the material more workable is beneficial. To increase concrete pumpability, a variety of chemical admixtures have been used, including air-entraining admixture, high-range water-reducing admixture, and finely divided admixture.

The properties of the combination determine which kind of chemical admixture to use in concrete and how much of it to add.
Air-entraining chemicals decrease bleeding and segregation while increasing the cohesiveness of concrete. Mineral admixtures increase the pumpability of concrete by lowering the rate and volume of bleeding.

Types of Admixtures and Their Functions in Pumpable Concrete

Air-entraining Admixture

Concrete that has an air-entraining admixture has better cohesion and workability. This considerably lessens the possibility of segregation, which is a big worry with pumpable concrete. It also lessens the concrete’s propensity to bleed.
Because there is less bleeding with air-entrained concrete compared with non-air-entrained concrete, the pipeline may be started up more easily after closure. Concrete bleeding lowers lubricant levels and raises the possibility of pipeline obstruction.
Table 1 shows the suggested air-entraining admixture dosage based on the maximum aggregate size. These limits shouldn’t be broken while pumpable concrete is being made since they are based on how resistant concrete is to cycles of freezing and thawing

Table- Recommended air contents for concrete resistant .

Figure: Result of air content in concrete

Mineral Admixtures

There are three categories for mineral admixtures:

1. Materials that are comparatively chemically inert, such as hydrated lime, crushed quartz, and limestone.

2. Cementitious materials include slag cement, hydraulic lime, powdered granulated blast furnace slag, and natural cement.

3. Pozzolan materials, such as silica fume, heated shales and clays, diatomaceous earth, fly ash of classes C and F, and volcanic glass.

Most of the materials mentioned above have particles that are smaller than cement. These materials’ smooth, thick surface texture and spherical particle form enhance a concrete mixture’s pumpability.
Finely split mineral additive improves the workability and pumpability of concrete and lowers bleeding rate and amount if the mixture does not contain enough fine particles.

Figure: Slump Test when admixture are used

Normal and High-Range Water-Reducing Admixture
Admixtures that reduce the water-cement ratio at a steady slump or boost workability of concrete are known as water-reducing admixtures.
Additionally, some admixtures that reduce water can entrain air, which enhances the pumpability of concrete. Concrete that needs to be pumped using a high-range water-reducing additive (superplasticizers) ought to be released and put in before its workability is compromised.
For flowing concrete, a high-range water-reducing additive is employed. Because it lowers pumping pressure and increases the rate and distance concrete can be pumped, flowing concrete is appropriate for pumping.

Anti-Washout Admixture
Concrete that is pumped under water becomes more cohesive when anti-washout admixtures are added. Synthetic or natural gums and thickeners based on cellulose are a few of instances of anti-washout admixtures.