Thursday, April 12, 2018

TYPES OF CEMENT


TYPES OF CEMENT

TYPES OF CEMENT
      Different types of cement are produced by altering their constituents proportion to gain required properties for specific purposes.
      Ordinary Portland cement (OPC)
      Rapid Hardening Portland Cement (RHPC)
      Low heat Portland Cement (LHPC)
      Sulphate Resisting Portland Cement
      High alumina Cement
      Blast furnace slag
      Colored cement
      Pozzolana cement
      White cement

Some generalization
      As C2S produces less heat, its content is more in low heat producing cements
      As C2S is more resistant to chemical attack, its content is more in cement mostly exposed to chemical attack 
      As C3S develops early strength, its content is more in cement like Rapid hardening cement
      C3A more in proportion when quick setting property is required
      Low heat producing cements are used in mass concreting
      Sulphate resisting cements are used where there is action of sea water
      These generalizations will also form the basis of cement classification.

Ordinary Portland Cement (OPC)
      It is a common type of cement
      It has adequate resistant to dry shrinkage and cracking
      It has less resistant to chemical attack
      It is not used for construction work exposed to Sulphate
       It is called Portland cement because its color resembles the stone quarried on the Isle of Portland of the British coast.

Uses of OPC
      In general concrete construction when there is no exposure to Sulphate in soil or ground
      In small structure where heat of hydration will not cause any defect

Rapid hardening Portland cement (RHPC)
      It develops high early strength as it contains higher percentage of C3S
      It contains large proportion of lime; other constituents remaining similar to OPC
      It is lighter than Portland cement
      Its curing period is small so it is economical
      It is not used for massive concrete structures
      Its strength in 3 days is same as the strength of ordinary Portland cement (OPC) in 7 days
      It is prepared by burning at higher temperature than that of OPC
Uses of RHPC
      It is used where early strength is desired like-
      For road pavement
      For cold weather concreting
      Where formwork is to be removed as early as possible

Low Heat Portland Cement (LHPC)
      It contains low percentage (5%) C3S (more heat producing) and more percentage (46%) C2S (low heat producing)
      It contains less lime than OPC; other constituent remains same as that of OPC
      It has less compressive strength
      It is not used for thin concrete structures
      It has little lower strength than OPC initially but afterwards it attains same strength as OPC
      Initial setting time is 60 minutes
      Final setting time is 10 hours i.e. 600 minutes

Uses of LHPC
      It is used in mass concreting like for dam, etc. as it produces less heat
      It is used in retaining walls

Sulphate Resisting Portland Cement
      In this cement, percentage of C3A is kept below 5% because C3A cannot resist chemical attack and hence the resulting cement will be more resistant to chemical attack (Sulphate attack)
      Uses-
      It is used in place exposed to Sulphate attack
      It is used in canal, culvert, etc.

High Alumina Cement
      It contains about 35% alumina
      It sets quickly
      It attains higher ultimate strength in short period
      It is completely resistant to Sulphate
      It is resistant to fire
      It is not affected by frost
      Its strength after 1 day is 40 N/mm2 and after 3 days is 50 N/mm2

Uses of High Alumina Cement
      It is used in chemical plants, furnace, where there is action of sea water
      It is used in colder region
      It is used in under water construction
      It is used during wartime emergency

Blast furnace slag
      It is made by grinding OPC clinker and granulated blast furnace slag
      It is cheaper than OPC as it is made from the waste product of furnace
      Low heat evolution
      It is not used in RCC structures as its early strength is less
      Uses
      It is used in mass concreting as less heat is produced
      It is used in dams, bridge abutment, retaining walls
      It is used in sea water construction as it has more Sulphate resistant

Colored cement
      5-15% coloring pigment is used before cement is finally ground
      Also called colocrete
      The commercial name of white and colored cement is “colocrete”, “rainbow cement”, “silvicrete”
      It is costlier than OPC
      Uses
      For finishing of floors, external surfaces
      Artificial marble, stair tread
      Texture panel faces, windows sill slabs, etc.

Pozzolana cement
      It is made by intergrinding OPC clinker and pozzolana
      Pozzolanic material added to OPC clinker is about 25%
      Pozzolana (silica and alumina in reactive form) is a silicious material containing 80% clay
      This cement has higher tensile strength
      It evolves less heat during setting
      It has water tightness
      It is resistant to expansion
      It is resistant to chemical attack and action of sea water

Uses of pozzolana cement
      It is used in hydraulic work like-
      Dams
      Weir, etc.
      In sewage work
      In laying concrete under water
White cement
      It is made from raw materials containing very little iron oxide and manganese oxide
      China clay is generally used together with chalk or limestone
      Oil is used as fuel for kiln to avoid contamination by coal ash
      It is expensive
      It dries quickly
      It has super aesthetic values
      It has high strength

Uses of white cement
      For floor finishing, plaster work, ornamental works, etc.
      In swimming pool, molding sculptures and statues, painting garden furniture, etc.
      For ready-made concrete and precast concrete blocks

Quick setting cement vs rapid hardening cement
Quick setting cement
Rapid hardening cement
Initial setting time = 5 minutes
Initial setting time = 30 minutes
Final setting time = 30 minutes
Final setting time = 600 minutes
It contains higher percentage of C3A and C4AF which helps in quick setting action and gypsum is also used in less amount so as to quicken setting
It contains higher percentage of C3S as C3S contributes to early strength
It is used for concreting work under water or running water as they require quick setting
It is used in roads, pavement, precast concrete as they require early strength

Summary of cement type uses
Examples of types of cement with
Resistant to Sulphate attack
Example of types of cement with
Low heat of hydration
Used to resist sea water action
Used in mass concreting like dams
High alumina cement
Blast furnace slag
Sulphate resisting Portland cement
Low heat Portland cement
Blast furnace slag
Pozzolana cement
Pozzolana cement


Purpose
Cement type
In chemical plants, furnace
High alumina cement
In road pavement, cold weather
Rapid hardening cement
Under water or running water
Quick setting cement
For aesthetic point of view
Colored cement, white cement


No comments:

Post a Comment

MOST RECENT

BITUMEN, ASPHALT, COAL TAR, CUTBACK BITUMEN

Ever wondered what is Bitumen? What is Asphalt? What is difference between these two? What is MC 30 Bitumen? What is cutback bitumen? We wil...