Concrete with fly ash (why it should be used)

Fly ash concrete is becoming increasingly popular in the construction industry due to the benefits of adding fly ash to concrete.

Fly ash is most commonly used as an additive or as a substitute for cement. Especially when the heat of hydration needs to be reduced in a dry environment or if a higher cement content needs to be used, fly ash is more commonly used.

Fly ash or pulverized fuel ash is the residue from the combustion of pulverized coal, which is collected from the combustible gases of thermal power plants by mechanical dust collectors or electrostatic precipitators or separators. Fly ash is also a combination of calcium, aluminum and silicon oxides, just like cement, but contains significantly less calcium oxide.

The particle size of fly ash is in the range of 1-100 microns (0.1 mm) and the average size is about 20 microns, which is the average particle size of Portland cement. .

Fly ash can be used as a raw material for many cement-based products. Some of the most common uses include pouring concrete, cinder blocks, and building bricks.

There are two different types of fly ash.

These are class F and C fly ash.

Class F Fly ash contains particles coated with a type of molten glass. It is able to resist the risk of expansion and sulfation.

Class C also resists expansion by chemical attack. Class C fly ash is most commonly used for structural concrete.

Typically, Class F fly ash is used in a dosage of 15 to 25 percent by mass of the cementitious material, while Class C fly ash is used in a dosage of 15 to 40 percent.

Fly ash can be used as an additive or partial substitute for cement. Generally, fly ash is used in the following three ways.

1. Partial replacement of cement. The ideal amount of pozzolan as a substitute is generally between 10 and 30 percent.
2. Partial replacement of aggregates. Fly ash can be used as a substitute for sand. Although there are positive effects such as initial strength, it is not economical
3. Simultaneous replacement of cement and fine aggregate.

BENEFITS OF USING FLY ASH

In terms of advantages and disadvantages, fly ash is a good substitute and also a good replacement material in concrete.

Above all, low carbon dioxide emissions, as a prerequisite for sustainable development, can be seen as one of the key factors that must be taken into account when defining the future.

The following key benefits can be achieved using fly ash:

1. Different target times are generated
2. Cold resistance
3. High increase in resistance (depending on application)
4. Can be used as an additive
5. Considered a material that does not shrink
6. Improve workability
7. Reduces cravings, permeability and bleeding
8. Reduces heat of hydration
9. The water-cement ratio can be reduced (compared to a mix without fly ash)
10. Reduce CO ₂ Emissions
11. Reduction of bleeding
12. Resistance to penetration of aggressive liquids and corrosion of reinforcement
13. Resistance to chlorides and sulfates

DISADVANTAGES OF FLYING ASH

Fly ash has some disadvantages.

These materials may not be suitable, especially for smaller scale constructions.

If concrete is removed with fly ash, special precautions are required in the concrete batching plant. In these cases the costs would be higher. The following factors can be considered as the main factors.

1. Slow gain in strength
2. Seasonal restrictions
3. Increased need for air-entraining agents
4. Increase in salt deposition due to higher proportion of fly ash