Testing methods of pozzolanas
Practical Action
This is determined by drying a sample in an oven and weighing to determine the
percentage weight loss.
2. Loss on ignition
The method is similar to that used in the Indian Standard
3. Chemical content
Silicon dioxide
Aluminium oxide and iron oxide
Calcium oxide
Magnesium oxide
Sulfur trioxide
Available alkalies
As with the Indian Standard, these tests are carried out using specified reagents and
the result is given as a percentage of the total weight.
Physical tests
4. Specific gravity
Specific gravity is measured using the ‘Le Chatelier’ flask.
5. Fineness
Fineness is calculated after wet sieving a sample of pozzolana on a No. 325 (45μm)
sieve.
6. Soundness
Soundness of a sample is a measurement of its tendency to crack, distort, pit or
disintegrate. The autoclave method is used. This method tests for expansion after a
certain period of time at elevated temperature in an autoclave.
7. Drying shrinkage
Again 3 specimens (3 of mortar and 3 of concrete) are incubated and measured for
shrinkage after 8, 16, 32 and 64 weeks. Length change data, reported as percent
increase or decrease in linear dimension to the nearest 0.001% is based on an initial
measurement made at the time of removal from the moulds.
8. Limits on amount of air-entraining admixture in concrete
Tests are carried out on hardened concrete containing a specified (neutralised Vinsol
resin) air-entraining admixtures for compressive strength, flexural strength, resistance
to freezing and thawing and length change.
9. Air entrainment of mortar
Calculation of the amount of air-entraining admixture required to produce a specified
air content in mortar.
10. Pozzolanic activity index with Portland cement
The pozzolanicity index is a number based on the compressive strength of sample
cubes such that:
Pozzolanicity activity index with Portland cement = A/B x 100
where, A is the average compressive strength of test mix cubes containing
pozzolana (psi / kPa), and
B is the average compressive strength of pozzolana free test cube mix (psi /
kPa)
11. Water requirement
Determination of water required to produce a specified flow in a pozzolana mix.
12. Pozzolanic activity index with lime
5