What Is Fly Ash Concrete? What Is The Difference Between Fly Ash And Cement?
What Is Fly Ash Concrete?
Fly ash is an important ingredient in concrete that has many benefits. Its use improves the workability of plastic concrete and the strength and durability of hardened concrete, making it very cost-effective.
Additionally, when fly ash is added to concrete, the amount of Portland cement can be reduced while still maintaining a high level of strength.
In terms of fresh concrete, fly ash provides excellent workability due to its spherical shape which helps in dispersion and effective filling of gaps within the mix.
It also works as an effective water reducer, resulting in higher strengths with lower water-cement ratios even at low cement contents.
In addition to these benefits for fresh concrete, tests have shown improved durability performance for fly ash-containing concretes when compared with plain Portland Cement Concrete (PCC).
So it is clear that incorporating fly ash into all types of concrete projects can bring about great improvements and cost savings.
Why Fly Ash Concrete Is Not Commonly Used?
Fly ash concrete, even though it is environmentally friendly, has not been commonly used due to its slower strength gain, seasonal limitation, and increased need for air-entraining admixtures.
Fly ash needs more time to cure and attain strength compared to traditional Portland cement resulting in longer lead times for construction projects.
Moreover, the availability of fly ash can vary seasonally or yearly depending on a region’s energy production methods which makes long-term planning difficult.
Lastly, increased use of fly ash in concrete leads to an increase in the amount of air-entraining admixtures needed; admixture amounts can be calculated by using trial mixes since there is no reliable data available yet.
What Is The Difference Between Fly Ash And Cement?
Fly ash and cement are two different components commonly found in concrete mixtures. Fly ash is a by-product of the burning of coal for energy production and is much finer than Portland cement (the most common type used).
This fine consistency enables it to occupy smaller voids that would normally be filled with water, giving the resulting concrete greater strength and reduced permeability when compared to a mix containing only cement.
What Are The Advantages Of Fly Ash In Concrete?
Fly ash use in concrete has numerous advantages, such as increased workability of plastic concrete and improved strength and durability of hardened concrete.
- Additionally, fly ash use is cost-effective as it allows for a reduction in the amount of portland cement used.
- Fly ash is particularly beneficial since it can help to reduce water demand, shrinkage cracks, permeability, and bleeding while also increasing the early strength of concrete.
- Altogether, these characteristics make fly ash an invaluable construction material when incorporated into concrete.
What Are The Disadvantages Of Fly Ash In Concrete?
Fly ash can have several disadvantages when used in concrete, including slower strength gain, seasonal limitation, an increased need for air-entraining admixtures, and an increase in salt scaling produced by higher proportions of fly ash.
These issues may be particularly concerning to contractors and engineers that are trying to meet aggressive construction schedules or high-quality standards.
While the use of fly ash can provide certain advantages over traditional Portland cement, it is important to consider any potential drawbacks as well.
What Is the Maximum Fly Ash Content in Concrete As Per IS 456?
According to the Indian Standard IS 456, the maximum fly ash content permitted in concrete is 35%, meaning that for every 100 kg of cement used, a maximum of 35 kg should be replaced by fly ash.
This ensures that no more than 35% of the total cementitious material content comprises fly ash. It is important to note that this limit applies to all grades of concrete including M30 and M50.
In addition, it is also worth noting that this replacement shall be done only after a thorough mix design process has been completed, which should determine the optimum amount which can be used in order to meet all strength requirements.
