Special Types of Cement and Storage of Cement

Special Types of Cement and Storage of Cement

Discover the world of Special Types of Cement: from rapid hardening to sulphate-resistant and more. Learn the art of proper Cement Storage to maintain quality and performance. Explore our comprehensive guide now!

Special Types of Cement

Special types of cement are tailored to meet specific construction needs and are designed with unique properties to enhance performance in various applications. Here are some special types of cement:

i) Rapid hardening cement (RHC):

• It is the type of cement which attains a higher rate of gain of strength in comparison to OPC and must not be confused with quick setting cement that only sets quickly.
• The strength of this cement at the age of 3 days is equal to the strength of OPC at the age of 7 days.
• This cement is produced by finely grinding the cement clinkers such that a specific surface area of not more than 3250 cm/gm and by increasing the proportion of C₃S (=56%).

Applications of RHC:

• i) Cold weather concreting
• ii) Pavement construction
• iii) Pre-fabricated structures
• iv) Where formwork is to be reused for speedy construction

Properties of RHC:

• i) Initial setting time = 30 min
• ії) Final setting time = 10 hrs (max)
• iii Compressive strength

1 Day = 16 N/mm²

3 Days = 27.5 N/mm²

• This Cement also offers higher resistance against frost action.
• The cost of RHC is approx. 10% more than OPC.

Note: RHC is subjected to higher shrinkage, and the water requirement for workability is also more in the case of RHC.

iI) extra Rapid hardening cement:

• It is the type of cement which attains a higher rate of gain of strength than rapid hardening cement.
• The strength of this cement at the age of 1 day is 25% more and at the age of 7 days is 10-15% more than the rapid hardening cement.
• This rate of gain of strength decreases with time, and the strength of the cement at the age of 90 days is the same as that of rapid hardening cement and OPC.
• This cement must be mixed, transported, placed, compacted, and finished within 20 min of the addition of water in it.
• This cement is produced by grinding the rapid hardening cement clinkers with 2% of CaCI₂ [Accelerator (Admixture)].
• Its application is the same as rapid hardening cement.

What is admixture?

Admixtures are added to concrete, mortar or grout mixture to achieve or improve desired properties in the fresh or hardened state. These are added in concrete to enhance specific properties such as workability, durability, early and final strength, etc.

iII) IRS T-40 Cement:

• It is also a special type of cement manufactured by Indian Railways to be used for the construction of railway sleepers.
• It is produced by finely grinding the cement clinkers and increasing the proportion of C₃S.

iV) quick Setting Cement:

• It is the type of cement which loses its plasticity comparatively earlier than OPC but does not attain early strength.
• This cement is produced by increasing the proportion of alumina and reducing the proportion of gypsum.

Applications:

i) Underwater construction
ii) Grouting operation (pressurised application of cement)

Properties:

• Initial Setting Time = 5 mins
• Final Setting Time = 30 mins

V) low heat Cement (LHC):

• The heat of hydration of this cement at the 7 days is not more than 65 cal/gm and at the age of 28 days is not more than 75 cal/gm.
• It is the type of cement that evolves lower heat of hydration than compared OPC.
• The cement is produced by reducing the proportions of C₃S, C₃A and increasing the proportion of C₂S to compensate for the lost strength on account of reducing C₃S).
• The cement offers higher resistance against the attack of sulphur and a slower the rate of gain of strength.
• This cement finds its application in mass concreting work example
• In hydraulic structures, foundations, etc.

Properties:

a) Compressive strength of this cement at the age of

• 3 days < 10 N/mm²
• 7 days < 16 N/mm²
• 28 days < 35 N/mm²

b) When tested be Le - Chatelier method and autoclave test, the expansion must not be more than 10 mm and 0.8%, respectively.

c) Setting Time

• Initial Setting Time = 60 mins
• Final Setting Time = 600 mins

VI) hydrophobic cement:

• It is the type of cement which do not reacts with water on its own.
• This cement is produced by intergrinding cement clinkers with water repellent film-forming substances like stearic and oleic acids.
• The cement finds its application where extreme environmental condition prevails:

Coastal areas and hilly areas and when a high storage period is required.

Note: In today's time, almost every cement is coated with this water repellent film.

Properties:

a) The specific surface area of hydrophobic cement not more than 3500 cm_²/gm
b) Average compressive strength should not be less than

3 days * 15.69 N/mm²
7 days * 21.57 N/mm²
28 days * 30.40 N/mm²

• The weak point of this cement is its small strength during the initial period because of the hydrophobic film on the cement grains. But strength at the age of 28 days is the same as that of OPC.

important question

What is the advantages of restricting the amount of C₃A up to 5% in sulphate resisting cement?

i) C₃A is responsible for the maximum heat of hydration so decreasing its amount helps in the reduction of the heat of hydration.
ii) C₃A is also responsible for the decrease in the sulphur resisting capacity of cement; thus, decreasing its amount helps in increasing its sulphate resisting capacity.

VII) sulphate resisting cement:

• It is the type of cement that offers higher resistance to the attack of sulphate than OPC.
• This cement is produced by intergrinding cement clinkers such that the proportion of lime and alumina is reduced in it.
• This cement finds its application wherever the chances of attack of sulphur on cement are more
  • i) Sewerage system
  • ii) Foundation work
  • iii) Where concrete pipes are to be laid in marshy areas
  • iv) Marine construction
  • v) Canal works

Properties:

a) Its compressive strength should be as follows:
3 days = 10 N/mm²
7 days = 16 N/mm²
28 days = 33 N/mm²
b) It should have the fineness of 4000 cm²/gm. The expansion of the cement is limited to 5 mm (Le-Chatelier test).
c) The IST and FST are the same as that of OPC.

What is Blast Furnace Slag?

It is the residue obtained after the extraction of metal from its ore

important question regarding Special Types of Cement and Storage of Cement

Why the initial setting time of low heat cement is more than Ordinary Portland Cement?

During the production of LHC, the proportion of C₃S and C₃A is reduced. And C₃A is responsible for the flash setting of cement (early setting); thus, due to the decrease in the amount of C₃A, the initial setting time of LHC is more than OPC.

VIII) Super sulphated cement:

• It is a type of cement that offers higher resistance to the attack of sulphur than the sulphate resisting cement (must not be confused with sulphate resisting cement).
• This cement is manufactured by intergrinding (80-85) % granulated blast furnace slag, (10-15) % hard burnt gypsum, 5% of cement clinkers.
• The application of this cement is the same as that of sulphate resisting cement.
• This cement can also be produced by increasing the proportion of ferric oxide, which has higher resistance against the attack of sulphur.

Properties:

a) Compressive strength should not be less than:
3 days ‡ 15 N/mm²
7 days ‡ 22 N/mm²
28 days ‡ 30 N/mm²
b) It should have a fineness of 4000 cm²/gm.
с) The expansion is limited to 5 mm, and the setting time is the same as that of OPC.

important question regarding Special Types of Cement and Storage of Cement

What are the advantages of super sulphated cement other than its sulphate resisting capacity?

The advantages of super sulphated cement are as follows:
i) In super sulphated cement, the amount of clinker is reduced to 5%, and the amount of slag is used up to (80-85) %, and slag is a residue thus, the cost of cement is reduced.
ii) The amount of C₃A, C₃S, C₄AF & C₂S is reduced (due to the low clinker content); thus, the heat of hydration is also reduced.

IX) portland slag cement:

• This cement is produced by intergrinding cement clinkers, hard burnt gypsum, and granulated blast furnace slag in specified proportions.
• This cement offers:
  a) Higher resistance against the attack of sulphur and chlorides.
  b) Better refinement of pore structures.
  c) Low heat of hydration
  d) Low cost
• The chemical requirement of this cement is the same as that of 33 grades cement.
• Specific surface area ‡ 2250 cm²/gm
  • Expansion is limited to 10 mm and 0.8% respectively on Le-Chatelier and autoclave apparatus
• The cement finds its application in mass concreting i.e., dams and foundations

X) portland pozzolana cement:

• The cement is produced by intergrinding the cement clinkers with (10-15) % of pozzolanic materials.
• Pozzolanic materials are essentially siliceous or aluminous compounds, which themselves do not possess any binding property, but when finely grinded reacts with lime released during the hydration of cement and results in the formation of a compound possessing binding property.
• This cement offers:
  • i) Higher water tightness
  • ii) Low heat of hydration
  • ili) Low cost
  • iv) Higher resistance against the attack of chemicals
  • v) Higher resistance against volume changes
  • vi) Slower rate of gain of strength, but the ultimate strength is comparable with OPC.

Properties:

a) Compressive strength is as follows:
3 days - 16 N/mm?
7 days - 22 N/mm?
28 days - 33 N/mm?
b) Fineness should not be less than 3000 cm²/gm; IST and FST are the same as OPC.
c) It finds its application in mass concreting work.

XI) high alumina cement:

• It is manufactured by grinding 40% of bauxite, 40% of lime, and 15% of iron oxide with a little silica and magnesia at a very high temperature.
• The alumina content should not be less than 32%, and the ratio of alumina to that of lime is 0.85 - 1.35.
• The resultant product is finely ground.
• The main ingredient is monocalcium aluminate (CA), which reacts with water to form dicalcium octahydrate hydro-aluminate.
  2(CaO.AL₂0₃.10H₂O) + H₂O → 2CaO.AL₂ 0₃.8H₂0 + 2Al(OH)₂
• The dicalcium hydro-aluminate gel consolidates, and hydration products crystalise.
• The rate of consolidation and crystallisation is high, leading to a rapid gain of strength.
  • i) It has high resistance against the attack of chemicals and acids.
  • ii) It offers higher resistance against high temperatures.

Properties:

a) Since C₃A is not present, it has good resistance against sulphur and has a high initial setting time.
Its initial setting time is up to 3.5 hrs.
The final setting time is up to 5 hrs.
b) After setting and hardening, Ca(OH)₂ is not leached as in the case of OPC, hence has higher durability
c) Specific surface area ‡ 2250 cm²/gm.
d) Expansion should not be more than 5 mm.
e) Compressive strength at the age of:
1 day is approx. 30 N/mm²
3 days is approx. 35 N/mm²

It finds its application in precasting and refractory concrete in industries.

Storage of Cement

Master the art of Cement Storage: Keep your cement dry and high-quality with proper storage techniques. Learn how to protect your investment for lasting construction success.

The precautions taken care during the storage of cement bags are as follows:

• i) The storage of the cement bags should be done in a building or a shed at the worksite that is moisture-proof, leak-proof, and dry.
• іi) The number of windows and close-fitting doors should be minimum in the building or shed where the cement is stored.
• iii) The stacking of cement bags should be done in the order in which they are received.
• iv) The gap between the cement bags should be kept minimum as far as possible.
• v) A space of 600 mm(minimum) should be kept between the stacks and the exterior walls.
• vi) The width of the stack should not be more than 3 meters or 4 bags in length.
• vii) To prevent the possibility of lumping up under pressure, the height of stacking of cement bags should not be more than 10 bags.
• viii) The stacking of cement bags should be done on wooden planks so as to keep about 150 mm to 200 mm clear above the floor.
• ix) To prevent the danger of toppling over in the stacks, having more than 8 bags in height, the arrangement of cement bags should be made alternatively lengthwise and cross-wise.

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