Did You Know
Q.1 What is pozzolana?
A.
Pozzolana is a natural or artificial material containing silica in reactive form. In other words, pozzolana is a siliceous or siliceous & aluminous material which it self possess little or no cementitious properties but in finely divided form, in presence of moisture, it reacts chemically to add certain properties of concrete. Fly ash, Micro-Silica, Rice-Husk, GGBS, Metakaoline are a few examples of pozzolonic materials.
Q.2 What is fly ash?
A. Fly ash is a finely divided residue resulting from the combustion of ground or powdered bituminous coal or sub bituminous coal (lignite) and transported by the flue gases of boilers fired by pulverized coal or lignite.
Q.3 Did you know the source of fly ash ?
A. Thermal Power Station and Industrial Plants using pulverized coal or lignite as fuel for boilers are the prime sources for getting fly ash.
Q.4 Did you know the categories of fly ash ?
A. There are three categories of ash available :-
- Bottom Ash :- Ash collected at the bottom of boiler furnace characterized by better geo- technical properties is termed as bottom ash. It is a good material for fill, road and embankment construction.
- Dry Ash :- Ash collected from different rows of Electro-static precipitators in dry form is termed as dry ash. It is used in the manufacture of PPC, Concrete & Cement mortar, Lime fly ash bricks, Building blocks, Aerated concrete blocks etc.
- Pond Ash :- Fly ash and bottom ash are mixed together with water to form slurry, which is pumped to the ash pond area. In ash pond area, ash gets settled and excess water is decanted. This deposited ash is called pond ash. This is used as filling materials including in the construction of roads & embankments. Selected pond ash can be used for manufacturer of building products like lime fly ash bricks/ blocks etc.
Q.5 Did you know that with the use of fly ash, several properties of concrete get improved and the overall cost/time of construction is also reduced substantially?
A. With the use of fly ash, a number of properties such as ultimate compressive strength, impermeability of concrete, corrosion resistance etc. get improved. Fly ash being cheaper than cement, results in overall saving the cost of the construction. Construction time is also reduced while using fly ash in Roller Compacted Concrete, where replacement of cement by fly ash can be as high as 70 %.
Q.6 Did you know the optimum % of cement that can be replaced by fly ash?
A. 35 % by weight of cement can be replaced by fly ash but instances are there where it has been successfully used up to 65% to 70%.
Q.7 Did you know that the triple blend combination can enhance the durability of concrete?
A. Combination of fly ash, micro silica & cement often termed as triple blend can enhance the various properties of concrete within the reasonable/ affordable cost limit.
Q.8 Did you know the fly ash /pozzolana based cement can be used in concrete structures in the extreme aggressive water/environmental exposure conditions?
A. Yes, pozzolanic materials such as, fly ash, micro silica, GGBS, Rice husk etc. in combination with OPC or PPC/PSC can sustain extreme aggressive water/environmental exposure conditions.
Q.9 Did you know the technical benefits for using fly ash in concrete/civil construction?
A. Use fly ash in civil construction imparts us the following benefits:-
- Increased ultimate compressive strength
- Improved workability
- Better pumpability
- Reduced segregation & bleeding
- Reduced permeability
- Reduced heat of hydration
- Reduced drying shrinkage
- Decreased creep
- Decreased alkali-aggregate reaction
- Increased durability
- Increased Corrosion Resistance
Q.10 Did you know where fly ash can be used?
A.
- Construction of roads & embankments
- Manufacture of Portland Pozzolana cement
- Manufacture of bricks/ blocks, aerated concrete blocks, light weight aggregates
- Back filling of open cast mines and stowing of under ground mines
- Manufacture of alum, paint and ceramics and other high value items.
