SOUNDNESS TEST OF CEMENT BY AUTOCLAVE
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- IS: 4031 (Part-3): 1988
APPARATUS
REQUIRED FOR THE TEST:-
- Cement Autoclave
- Balance
- Length Comparator
- Graduated glass cylinder
- Modulus: 25×25×280 mm (internal length)
- Thermometer
 |
| Autoclave |
PROCEDURE OF
THE TEST:-
- The method shall be thinly covered with mineral oil. After this operation the reference insert shall be set to obtain an effective gauge length of 250 mm.
- A cement paste shall be formed taking 800 g of cement with sufficient water to give a past of standard consistency.
- Immediately after the mixing the test specimen shall be moulded in one or two layers, each layer being compacted with the thumb pressing the paste into corners.
- After the top layer has been compacted the paste shall be cut off flush with the top of the mould.
- During the operating the mixing & moulding the hand shall be protected with rubber gloves.
- After the mould has been filled, it shall be immediately placed in moist cabinet for at least 24 hours.
- After (24 ± 1/2) hours the specimen shall be removed from the moist cabinet, measure for length (L1) & shall be placed in the autoclave at room temperature.
- The autoclave shall contain enough water to maintain an atmosphere of saturated steam vapour during the entire period of the test.
- To prevent air to escape from the autoclave during the early portion of the heating period the vent value shall be lift steam being to escape.
10. The value
shall then be closed & the temperature of the autoclave shall be raised at
such rate as will bring the gauge pressure of the steam to 2.1 MPa in (1 to 1¼)
hrs. & maintained for three hours.
11. At the
end of three hours, the heat supply shall be shut off & the autoclave
cooled at the rate such that the pressure shall be less than 0.1 MPa at the end
of the hour.
12. The autoclave shall be less than be opened & the test specimen immediately
placed in water at a temperature above 90 °C.
13. The
water surrounding the bars shall be than cooled at a uniform rate by adding
cold water so that the temperature of water shall be lowered to 25°C to 29°C in
15 minutes.
14. The
water surrounding the specimen shall then be maintained at 25°C to 29°C in
15 minutes when the specimen shall be surface dried & their lengths
measured again.
15. Measure the length (L2) of the specimen when it is surface
dry.
CALCULATIONS
AND REPORTING:-
The difference in lengths (L1 – L2) of the test specimen
before & after autoclave shall be calculated to the nearest 0.01% of the
effective gauge length & shall be reported as autoclave expansion of
cement.
i.e. Soundness of
cement = L1 – L2,
Where,
L1 = Length measured after curing for a period of 24 hours
in a moist room.
L2 = Length measured after completion of autoclave test.
A contraction (negative expansion) is indicated by
prefixing a (–) sign to the percentage expansion reported.
Type/Name Of cement
|
Reference Indian Standard
|
Expansion of Soundness %, (max.)
|
OPC (33)
|
IS:269-1989
|
0.8
|
OPC (43)
|
IS:8112-1989
|
0.8
|
OPC (53)
|
IS:12269-1987
|
0.8
|
Rapid Hardening
Cement
|
IS:8041-1990
|
0.8
|
Low Heat Cement
|
IS:12600-1989
|
0.8
|
Portland Pozzolana
Cement
|
IS:1489-1991(part 1)
|
0.8
|
PSC
|
IS:455-1976
|
0.8
|
SRC
|
IS:12330-1988
|
0.8
|
Masonry Cement
|
IS:3466-1988
|
1.0
|
IRS-T-40
|
Railway standards
|
0.8
|
Super Sulphated
Cement
|
IS:6909-1990
|
Not
specified
|
High Alumina
Cement
|
IS:6452-1976
|
Not specified
|
TECHNICAL
DISCUSSIONS :-
- Volume expansion in cement mortar or in cement concrete is caused by the presence of unburnt lime (CaO), dead burnt MgO and also CaSO₄.
- By Autoclave method we only find out presence of unburnt lime (CaO) and magnesia (MgO).
- Magnesia content allowed in cement is limited to 6%.
- Indian standard specification stipulates that cement having a magnesia content of more than 3% shall be tested for soundness by Autoclave test which is sensitive to both free magnesia and free lime.
- No satisfactory test is available for deduction of unsoundness due to an excess of calcium sulphate. But it can be easily determined by chemical analysis.
