Types of Cement presentation, Lecture notes of Reinforced Concrete Design

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Cement

Rey Kevin B. Ortuoste

Extraordinary

Structures!

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When mixed with

aggregates and water

develops into concrete.

Manufacture of

Portland Cement

RAW MATERIALS

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Calcareous Materials

-limestone or chalk

Argillaceous Materials

-shale or clay

TWO KINDS OF

PROCESSES

Wet Process

Dry Process

They both consists of grinding of raw

materials then intimately mix them in

certain proportions depending on their

composition and purity. Next is the

materials are sent in a kiln to burn it

at a temperature of about 1300 to

1500°C. The material then fuses to

form nodular shaped clinker. The

clinker cooled and ground into fine

powder. 3-5% gypsum is then mixed

into the powder to complete the

manufacturing of Portland Cement

Manufacture of

Portland Cement

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-The process when water and

cement are mixed together, a

reaction takes place called

“hydration of cement”.

-Is an exothermic(produces

heat) reaction in nature. The

heat liberated in the process of

hydration is called “heat of

hydration”.

Calcium Silicate Hydrates

-the basis of determining good

concrete properties

-makes up 50-60% of the volume

of solids in a completely hydrated

cement paste.

Calcium

Hydoxide -Reacts with sulphates present

in soils or water to form

calcium sulphate which causes

concrete deterioration known

as sulphate attack.-consists of 20-25% of solids in

the hydrated paste.

Type of Cement

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1.) Ordinary Portland Cement(OPC)

-The most important type of cement

-It is made possible to upgrade the qualities of

Portland cement by using:

a. High quality limestone

b. Modern equipment

c. Closer on line control of constituents

d. Maintaining better particle size distribution

e. Finer grinding and better packing

-manufacturing of OPC has been decreasing all over the

world due to the popularity of blended cements that has

a. Lower energy consumption

b. Environmental pollution

c. Economic and other technical reasons

Type of Cement

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2.) Rapid Hardening Cement

-develops strength rapidly

-also known as high early strength

-should not be confused with quick setting cement(which only

sets quickly but doesn’t develop strength rapidly

-develops a strength at 3days with the same strength as of

OPC at seven days

-attributed to the higher fineness of grinding and higher C 3

S

with lower C 2

S

-produces greater heat of hydration in early period that is why

rapid hardening cement are not advised to be used in mass

construction such as dams. -produces greater heat of hydration in early period that is why

rapid hardening cement are not advised to be used in mass

construction such as dams.Recommended use:

a.) Pre-fabricated concrete construction

b.) Where formworks are required to be removed early for re-

use

c.) Rapid repairs like potholes on roads

d.) Cold weather where freezing damage of concrete be

reduced

Type of Cement

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4.) Sulphate Resisting Cement

-OPC is susceptible to the attack of sulphates

-sulphate attack can be accelerated by alternating of wetting and

drying which usually takes place in marine conditions.

-to counter the attack, the use of low C 3

A like the sulphate

resisting cement which limits C 3

A content to 5%.

Recommended Use:

a.) Marine Conditions

b.) Foundations and basements where soil is infested with

sulphates

c.) Fabrication of concrete pipes which are likely buried in

marshy region

d.) Construction of sewage treatment works

Type of Cement

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5.) Portland Slag Cement PSC

-obtained by mixing Portland cement clinker, gypsum, and

granulated blast furnace slag

-low heat of

hydration -developed to utilize blast furnace slag (from factories with blast

furnaces) -Portland clinker is mixed with 20-65% granulated slag

-is similar to OPC with respect to fineness, setting time, soundness

and strength. -can be used in mass construction

Type of Cement

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7.) Super Sulphated Cement

-manufactured by grinding together 80-85% granulated slag, 10-15%

hard burnt gypsum, and 5% Portland cement clinker.

-low heat of

hydration -sensitive to deterioration during storage when compared to OPC

-has high resistance to sulphate due to high alumina content

Type of Cement

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8.) Low Heat Cement

-produces low heat at a low rate during hydration process

-achieved by reducing the amount of C 3

S and C 3

A

-sensitive to deterioration during storage when compared to OPC

-low heat of hydration means slow rate of gain of strength but

the ultimate/final strength of low heat cement is the same as

that of OPC -Recommended Use:

a.) Massive concrete structures like dams.

Type of Cement

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Advantages of PPC

1.) Costly clinker is replaced by cheaper pozzolanic material

2.) Soluble calcium hydroxide is converted into insoluble

cementitious materials.

5.) Since PPC is slightly lighter than OPC, the volume of PPC in a

50kg bags is greater when compared to OPC.

6.) Long-term(months) strength of PPC is higher than OPC if

enough moisture is available for continued pozzolanic action.

3.) Low heat of hydration

4.) Finer than OPC, therefore it improves the pore size

distribution which reduces micro cracks

Disadvantages of PPC

1.) Rate of development of strength is initially slower than OPC

2.) Setting time is longer

Type of Cement

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10.) Air-Entraining Cement

-Introduces air bubbles in the concrete to make space for the water

to expand when it freezes. It helps reduce the damage freezing can

do to concrete. Types of air-entraining agents used in making Air-Entraining

Cement a.) Alkali salts of wood resins

b.) Synthetic detergents of the alkyl-aryl sulphonate type

c.) Calcium lignosulphate derived from the sulphite process in

paper making d.) Calcium salts of glues and other proteins obtained in the

treatment of animal hides

Type of Cement

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12.) High Alumina Cement

-obtained by fusing of alumina and calcareous materials then

grinding the resultant product to a fine powder

-Raw materials: limestone and bauxite

-The fusion takes place at a temperature of about 1550-1600°C

-Liquid state cement is maintained in the furnace then proceeds to

the casts and cooled.

-The casts are known as

pigs. -After cooling the cement mass resembles a dark, fine grey compact

rock resembling the structure and hardness of basalt rock.