| Sun May 07, 2017 | Total posts : 1 |
|  Topic: Selection of cement ..
Is it good to use PPC cement for basement (ACC Suraksha)..
Please suggest the best cement that to be used in different stages of construction like basement, walls, columns,beams, plastering etc..
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| Mon May 08, 2017 | Post #1 | S L Gupta (Civil Engg)
Join date: Mar 2008 | Dear Sir,
Types of Cement
For engineering purposes, there
are many types of cement but in general, ‘Ordinary Portland Cement’
(OPC) which is available in three grades should be used for house
construction
33 Grade Ordinary Portland Cement
This
ordinary 'Portland' cement is used maximum in the country. It is more
suitable cement for masonry and general concrete works where the members
are not taken to very high stresses. It is not suitable where
‘Sulphate’ is in the soil or in the ground water.
43 Grade Ordinary Portland Cement43
grades of cement are used where high early strength in 1 to 28 days
range is required. These days the ‘Structural Engineers’ propose these
cements mainly for RCC works where a member takes high tensile stress.
53 Grade Ordinary Portland Cement
53 grades of cement are used where high early strength in 1 to 28
days range is required. These days ‘Structural Engineers’ propose these
cements mainly for RCC works, where a member takes high tensile stress.
Caution in the use of 53 grade cement in construction:
The strength of 53 grade cement does not increase much after 28th day
because of early gain while 33 grade cement continues to gain strength
after 28th day.
In addition, due to faster hydration process,
the concrete releases heat of hydration at much faster rate initially
and release of heat is the highest in case of 53 grades. The heat of
hydration being higher, the chances of micro-cracking of concrete is
much greater. Thus during initial setting period of concrete, the higher
heat of hydration can lead to the damage of micro-cracking within the
concrete which may not be visible at surface.
This cracking is
different from shrinkage or cracks which occur due to faster dryness of
concrete in windy conditions. The situation can be worse when we tend to
increase the quantity of the cement in concrete with a belief that such
increments are better for both strength and durability of concrete.
Thus
it is very essential to be very careful in advance that higher grade
cement specially GRADE 53 SHOULD be used only where such use is
warranted for making the concrete of higher strength and also where good
quality assurance measures are in place by which proper precautions are
taken to relieve the higher heat of hydration through chilling of
aggregates or by proper curing of concrete
Various Colors of Cement
1. Grey = Color of OPC cement
2. Blackish = Color of PPC Cement
3. White = Other color of Cement
Various Brands of Cement
1. ACC
2. J.K.( Shakti Laxmi)
3. Birla ( Chetak Mehar ,Uttam, Khauraho, Manglam)
4. Shree
5. Prism
6. Dig Vijay
7. Ambuja
8. CCI
9. Vikram
10. Jay Pee Rewa
11. Binani
12. Shri Ultra
13. L. & T.
Specification of Cement
The
cement required for construction should be factory-manufactured from a
reputed manufacturer. It must not be from the local plant manufacturer.
Care should be taken that the cement is properly packed from the
factory, not be hand packed locally. While taking supply of cement
manufacturing date, grade and type should be checked. The cement should
not be more than six weeks old from the date of manufacturing.
Precautions While Purchasing Cement
Cement is the
most important raw material used in a building. You should ensure the
quality of ‘Cement’ using the following guidelines.
1. The cement should be factory manufactured instead of plant manufactured.
2. The cement should be packed in the bags of synthetic jute or polypropylene bags.
3. The cement bags should not be hand stitched.
4. The cement bag should bear manufacturer's name or his trade mark on it if any.
5. The cement bag should bear the grade and type of cement.
6. The cement bag consignment must have identification mark on package.
7. The cement bag should indicate the date of manufacturing.
8. One cement bag should have 50 Kg. weight.
9. The cement bags should not be older than six weeks from the date of manufacturing.
10. Do not purchase cement bags which are partially set due to moisture. Do not purchase if there are small lumps in the bags.
11. Do not purchase cement bags which are pressed or have lumps due to high pressure of stack having more than 10 to 12 bags.
12. Do not take cement bags which are torn by side and stitched in later.
Precautions While Transporting Cement Bags
1. Care should be taken to carry the bags in a clean vehicle which is
not dustier or on earth etc. It will reduce the strength of the cement.
2. During monsoon season the cement should be carried under covered Polythene or ‘Tarpaulin’.
3. Care should be taken that the labor should not tear the bags while loading and unloading the cement bags.
Precautions While Stacking Cement at Site
Store cement in a moist proof storage area other wise quality of cement will be affected.
1. Cement should be stacked in a shed/fumes, which is dry, leak proof and moisture proof.
2. Cement should be placed on dry brick floors, on wooden crates or on the planks.
3. In any case, the cement bags should not be stored on the earth.
4. The stack should not be higher than 10 bags to avoid lumps under pressure.
5. The cement bags should not be stacked with outer wall.
6. Cement from different manufacturers should be stacked separately.
7. The cement should be used on first come first used basis.
8. During monsoon season cement bags should be covered with polythene.
9. The cement bags should be kept close together to reduce air circulation.
Caution:
1.
When construction work is given to a contractor, make sure he takes
proper care of the cement. A lot of time contractors do not care for
proper storage of the cement at site as it costs them labor time
(money). This results in reduction of strength of cement as the table
below shows.
2. In some cases it has been seen that after laying the
RCC slab on some part of the building, the contractor dismantles his
temporary store at the site and places cement on ground floor of the
building which is under construction. This is not good as the cement
bags may draw moisture from the floor and walls, as the new building is
wet due to construction work in progress, which results in reduction of
strength in cement.
Reduction in Cement Strength Due To Storage
| S. No |
Storage Period |
Reduction in Strength |
| 1 |
Fresh cement |
Nil |
| 2 |
Three months old |
20% |
| 3 |
Six months old |
30% |
| 4 |
12 Months old |
40% |
| 5 |
24 Months old |
50% |
1. Due to absorption of moisture by cement during storage, cement retards in hardening and reduces the strength. 2.
It is okay for cement to absorb up to 1.2% moisture as this level of
moisture is acceptable but if absorption exceeds 5%, the cement is
destroyed for all practical purposes. 3. Different types of cements should not be mixed while using them for constructional purposes.
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Basement-Construction Questions (38) | |
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