CEMENT



 CEMENT

The quality of various cements is to be determined on the basis of its conformity to the performance characteristics given in the respective BIS Specification for those cement. Any trade name indicating any special features not covered in the standard or other special performance characteristics sometimes claimed/indicated on the bags alongside the ‘Statutory Marking’ shall not be a criteria for selecting cement.

1. Cement identification

Prior to carrying out a concrete mix design, cement identification should be recorded. Cement Identification chart shall be prepared with the following identification markings on the cement bag.

  1. Name of cement company.
  2. Place of the factory.
  3. Type of cement (Ordinary Portland cement, Portland Pozzolana cement etc.).
  4. Grade of cement (28 day compressive strength) with the relevant BIS code number.
  5. Date of manufacture.

2. Requirements

  1. The various types of cement shall comply with the respective BIS code as specified below:
  1. Ordinary Portland cement 33 grade-IS:269.
  2. Ordinary Portland cement 43 grade-IS:8112.
  3. Ordinary Portland cement 53 grade-IS:12269.
  4. Rapid hardening Portland cement-IS:8041.
  5. Portland pozzolana cement-IS: 1489 (Part-1).
  6. Portland blast furnace slag cement -IS: 455.
  7. Sulphate resistant Portland cement-IS: 12330.
  8. High Alumina Cement-IS: 6452
  9. Supersulphated Portland Cement-IS:6909
  10. Low Heat Portland Cement -IS:12600
  11. Masonry Cement- IS:3466
  12. White and Coloured Portland Cement-IS:8042
  13. Water Repellent Cement-IS:8043
  1. Cement shall be delivered to the Site in sealed and branded bags, or in the manufacturer’s containers, bearing the manufacturer’s name, cement type and date of manufacture, in batches not exceeding 100 tonnes.
  2. Cement shall be stored at the Site in such a manner, as to prevent its deterioration, intrusion of moisture and foreign matter. It must be kept dry at all times. Immediately upon arrival at the Site, the Cement shall be stored in:
  1. Bins or silos designed for the purpose. It shall be tight and provide for free movement to discharge opening, or
  2. Dry, weather tight and properly ventilated structures with floors raised a minimum of 450 mm above the ground with adequate provision to prevent absorption of moisture.
  1. All storage facilities shall be subject to the approval of the Engineer, and shall be such as to permit easy access for inspection and identification. Prolonged storage of cement at Site is to be avoided. An indicative rate of such deterioration is given in table.

Table: Rate of deterioration of cement against storage period

Period of storage of cement

Minimum expected reduction in strength at 28 days (%)

Fresh

0

3 months

20

6 months

30

1 year

40

2 years

50

 

Cement used in the Works shall be free flowing and free from lumps.
  1. In no case shall bagged cement be stored in stacks more than eight bags high.
  2. A free passage of at least 1 m shall be left between the cement and the sidewalls of the structure.
  3. Different types of cement shall be kept in clearly marked separate storagefacilities.
  4. Cement delivered to Site in drums or bags by the supplier or manufacturershall be stored in the drums or bags until used in the Works.
  5. Any cement in drums or bags which have been opened shall be usedimmediately.
  6. It is good practice to move cement out of the storage shed using the ‘first–in-first-out’ scheme.
  7. Cement that has partially or fully caked in storage will not be permitted in workand shall be immediately removed from the storage area. Any bag or package orsample of cement which has been damaged, or rebagged or in any way hasdeteriorated shall be rejected either as an individual bag or package or as thewhole consignment in which such bag, package or sample is contained, asadvised by the Engineer.
  8. Where site limitations preclude the storage of cement in Site, cement shall bestored at a central location and shall be delivered daily as required to specificjob sites.
  9. The weighing machines which shall be keptpermanently in each shed for checking the weight of the bags or barrels ofcement. The weighing machines shall be calibrated by an independent agency.The Engineer shall have access at all times to the cement storage sheds.
  10. During transport and storage, the cement shall be fully protected from all-weather elements.
  11. Any consignment of cement not used within two months from the date ofmanufacture and cement which in the opinion of the Engineer is of doubtfulquality shall not be used in the Works, until it has been retested and test resultsheets showing that it complies in all respects with the specification andrelevant standards have been delivered to the Engineer.
  12. Cement stored for longer than 28 days shall be tested prior to use to check fordeterioration, and any cement which fails the test shall not be used in theWorks.

3.Volume of One Bag of Cemect:

      Density of Cement =1440 Kgs/m³

      Mass of 1 Cement Bag = 50 Kgs

      Volume of One Cement Bag =Mass/Density =50/1440 =0.0347 m³

4. Sampling and testing

The  manufacturer’s certificate shall be made available for each supply ofcement.

  1. The cement must be subjected to various tests indicated in table asstipulated in BIS Specifications.
  2. Sampling of cement for testing shall be as per IS: 3535.
  3. The minimum weight of the final sample taken should be 6 kg and shall bestored in an airtight container until testing.
  4. Unless specified, the following tests shall be carried out for cement in complywith respective Indian Standards as specified in table.

Test for Cement

Test

Code

Permissible value

Frequency

Fineness

IS: 4031

(Part 1,

2 & 15)

Specific surface not less than

225 m2 /kg

1 test for every 50 tonnes or

part thereof.

(Same grade and brand)

Soundness

IS: 4031

(Part 3)

Not to exceed 10mm in

Le-Chatelier mould

- do -

Setting time

IS: 4031

(Part 1)

Initial setting time >30 mins.

Final setting time <600 mins.

- do -

Compr.. strength

At 72±1 hours

At 168±2 hours

At 336±3 hours

At 672±4 hours

 

IS: 4031

(Part 6)

33 Grade 43 Grade 53 Grade

16MPa       23MPa     27 MPa

22MPa       33MPa     37 MPa

33MPa       43MPa           -

-                     -             53 MPa

 

3 specimens for

each lot.

NOTE: For sample lots less than 50 bags, these tests need not be insisted.

RELATED CODES

1.IS:269-33 Grade ordinary Portland cement.

2.IS:455-Portland slag cement.

3.IS:1489-Portland pozzolana cement.

   (Part-1)-Fly ash based.

    (Part-2)-Calcined clay based.

4.IS:3535-Methods of sampling hydraulic cements.

5.IS:4031-Methods of physical tests for hydraulic cements. 

    (Part-1 to 14)

6.IS:4032-Methods of chemical analysis of hydraulic cements.

7.IS:4845-Definitions and terminology related to hydraulic cement.

8.IS:4905-Methods for random sampling.

9.IS:8041-Rapid hardening Portland cement.

10.IS:8043-Hydrophobic cement.

11.IS:8112-43 Grade ordinary Portland cement.

12.IS:12269-53 Grade ordinary Portland cement.

13.IS:12330-Sulphate resisting Portland cement.

14.IS:12600-Low heat Portland cement.

PORTLAND CEMENT :

It is a cementing material resembling a natural stone quarried from Portland in U.K. Portlandcement may be defined as a product obtained by finely pulverizing clinker produced bycalcining to incipient fusion, an intimate and properly proportioned mixture of argillaceousand calcareous materials. Care must be exercised in proportioning the raw materials so that theclinker of proper constitution may be obtained after burning.

The ordinary Portland cement has been classified as 33 Grade (IS269:1989), 43 Grade(IS 8112:1989), and 53 Grade (IS 12669-1987). The physical requirements of all these three typesof cement are almost same except for compressive strength and are as follows:

Sl.No

Physical requirement   

Method of testing

Grade

33

43

53

1

Fineness (Sp. Surfacein m2/kg)

Blaine's airpermissibility

225

225

225

2

Soundness

Le ChatelierapparatusAutoclave

10mm

0.8%

10mm

0.8%

10mm

0.8%

3

Setting time Initial (min)

Final (max)

Vicat apparatus

30

600

30

600

30

600

4

Compr..strength (MPa) not less than

72 ± 1 hr

168 ± 2 hr

672 ± 4 hr

 

 

16

22

33

 

23

33

43

 

27

37

53

IS:10262 has classified the OPC grade-wise from A to F based on 28 day compressivestrength as follows.

    Category   Strength (MPa)

A             32.5 – 37.5

B             37.5 – 42.5

C             42.5 – 47.5

D             47.5 – 52.5

E             52.5 – 57.5

F             57.5 – 62.5

Accordingly the 33, 43 and 53 grades of cement correspond to categories A, C and E,respectively. However, most of the 43-grade cements available in the market fall in category Dand that 53-grade cements in category F.

Oxide

Function

Composition(%)

CaO

Controls strength and soundness. Its deficiency reduces strength and setting time

60-65

SiO2

Gives strength. Excess of it causes slow setting.

17-25

Al2O3

Responsible for quick setting, if in excess, it lowers the strength.

3-8

Fe2O3

Gives colour and helps in fusion of different ingredients.

0.5-6

MgO

Impacts colour and hardness. If in excess, it causes cracks in mortar and concrete and unsoundness

0.5-4

Na2O + K2O

TiO2

P2O5

SO3

These are residence, and it in excess cause efflorescence and cracking Makes cement sound

0.5-1.3

0.1-0.4

0.1-0.2

1-2

Note :

1. The rate of setting of cement paste is controlled by regulating the ratio SiO2/(Al2O3+ Fe2O3).

2. Where development of much heat of hydration is undesirable, the silica content is increased to about 21 percent. and the alumina and iron oxide contents are limited to 6 percent each.

3. Resistance to the action of sulphate waters is increased by raising further the silica content to 24 percent and reducing  the alumina and iron contents to 4 percent each.

4. Small percentage of iron oxide renders the highly siliceous raw materials easier to burn. However, if these are in excess, a hard clinker, difficult to ground, is produced. When iron oxide combines with lime and alumina to form C4 AF, it neutralizes some of the undesirable properties contributed by alumina when combined with lime alone. When iron oxide combines with lime alone, it promotes instability.

5. The alkalis accelerate the setting of cement paste

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