|
Mechanically,
fly ash also pays dividends for concrete
production.
Because
fly
ash particles
are small,
they effectively fill voids.
Because
fly ash particles are hard
and
round, they have a “ball
bearing” effect that allows concrete to be
produced
using less water. Both characteristics contribute to enhanced concrete
workability and durability.
IS 3812 (Part 1) :2003
(Pulverized Fuel Ash
— Specification for for use as
Pozzolana in Cement, Cement Mortar and Concrete) specifies
Physical
requirements for Fly ash as tabulated below:
| Physical
Requirements |
| S.No
|
Characteristics
|
Requirements
|
| 1
|
Fineness
- Specific surface in m2/kg by
Blaine’s
permeability method, min |
320
|
| 2
|
Particles
retained on 45 micron IS sieve (wet sieving) in percent, Max
|
34
|
| 3
|
Lime
reactivity - Average compressive in
N/mm2, Min
|
4.5
|
| 4
|
Compressive
strength at 28 days in N/mm2, Min |
Not
less than 80 percent of the strength of corresponding Plain cement
mortar cubes |
| 5
|
Soundness
by autoclave test expansion of specimens, percent, Max
|
0.8
|
Note: Fly ash of
fineness 250 m2/kg (Min) is also permitted to be
used in the
manufacture of Portland pozzolana cement by intergrinding it with
Portland
cement clinker if the fly ash when ground to fineness of 320 m2/kg
or to the
fineness of the resultant Portland pozzolana cement whichever is lower,
meets
all the chemical & physical requirements specified in this
standard.
|
