Lecture 01: Introduction To Concrete Technology

11CE 106 Civil Engg. Materials and Concrete Technology By. Dr. Khan Shahzada

CE-106 Civil Engineering Materials and Concrete Technology

Concrete

CONCRETE everywhere around us

Ancient Roman were probably the first to use concrete a word of Latin origin based on hydraulic cement , that is a material which hardens under water.

Or Concrete is a composite material wherein a binding material

mixed in water on solidification binds the inert particles of well graded fine and coarse aggregates

2

Concrete Cont

Constituents of Concrete

Cement

Aggregates

Water

Admixtures

CE 106 Civil Engg. Materials and Concrete Technology By. Dr. Khan Shahzada

23

Concrete Cont

Uses of Concrete Roads Buildings Bridges Sidewalks Runways Canals Mines Tunnels Dams Sewer pipes Railway ties Manholes Nuclear Installations etc


4

Concrete Cont

Concrete

Concrete should be

Hard Durable Strong Dense Non porous Fire resistant

Economical

Typical Composition by volume

Cement: 7-15% Water: 14-21% Aggregate: 60-80%


35

Cement Cont


Setting of Cement

Initial Setting Time:

The time after mixing of cement with water at which the paste or mortar or concrete can no longer be properly mixed, finished, or compacted is known as initial setting time.

Final Setting Time:

The time at which the mortar or cement paste or concrete gain sufficient strength and hardness.

Assignment (Setting of cement in detail)

6

Concrete Cont

Concrete Versus Steel

USA

Concrete consumption 5 times by weight of steel

Other Countries

Concrete consumption exceeds 10 times by weight of steel

More than 1 ton/year/person

Man consumes no material except water in such tremendous quantities


47

Cement

Portland cement is the name given to cement obtained by intimatelymixing together calcareous and argillaceous or other silica-, alumina- andiron oxide bearing materials. Burning them at a clinkering temperatureand grinding the resulting clinker.

From the definition of port land cement given above, it can be seen thatit can is made primarily from a combination of calcareous material, suchas limestone or chalk, and of silica and alumina found as clay or shale. The process of manufacture of consist of essentially of grinding thematerials into a very fine powder, mixing them intimately in predeterminedproportions and burning in a large rotary kiln at a temperature of about1400C (2550F) when the material sinters and partially fuses into clinker. The clinker is cooled in a ground to a fine powder, with some gypsumadded, and the resulting product is the commercial Portland cement usedthroughout the world.


8

Cement Cont


oferrite

2CaOSiO2

59

Cement Cont


10

Cement Cont


Hydration of cement

Chemical reaction between cement and water is called hydration of cement.

Heat of Hydration

In common with many chemical reactions the hydration of cementcompounds is exothermic and the quantity of heat (in joules) pergram of hydrated cement evolved upon complete hydration at agiven temperature is defined as the heat of hydration.

Assignment (Hydration and Heat of Hydration in detail)


Ordinary Portland Cement (Type-I) This is the most common type of cement in use. Ordinary Portland cement is highly suitable for use in general concrete construction when there is no exposure to sulfates in the soil or groundwater.

Rapid hardening Portland Cement (Type-III) It develops strength more rapidly and is also called high early strength cement. The increased rate of gain of strength of R.H.C is achieved by a higher C3S content, sometimes as high up to 70 %, and by finer grinding of the cement clinkers. R.H.C is used where a rapid strength development is desired for example;

When formwork is to be removed early for reuse. where sufficient strength for further construction is required as quickly as

possible. In cold areas the use of cement with a high rate of heat of liberation may prove a

satisfactory safeguard against early frost damage. But the R.H.C should not be used in Massive structure as a high rate of heat development will cause cracking.

Types of Cement


Special Rapid hardening Portland Cement

These are specially manufactured cements which are highly rapid hardening.

Ultra high early strength Portland Cement This cement contains no admixtures and is therefore suitable for use in reinforced and Prestressed concrete. The rapid strength development is due to the very high fineness of cement (700 to 900 m2 /Kg) and a higher gypsum content, but this does not affect long term soundness. Typical uses are early prestressing and urgent repairs.

Extra rapid hardening Portland Cement This cement is obtained by intergrinding CaCl2 with R.H.C. The quantity of CaCl2should not exceed 2 % as CaCl2 is deliquescent (to become liquid), so the extra R.H.C should be stored under dry conditions and it should generally be used with in one month of dispatch from the cement plant. Extra R.H.C is suitable for cold weather concreting, or when a very high early strength is required, but should not be used for reinforced concrete because of the risk of corrosion.

Types of Cement Cont..


Regulated-Set Cement or Jet CementThis cement consists essentially of a mixture of Portland cement and calciumflouraluminates with an appropriate retarder (usually citric acid). The settingtime (1 to 30 minutes) can be controlled in the manufacturing process of thecement as the raw materials are intergrind and burnt together, while the earlystrength development is controlled by the content of the calciumflouraluminate. This cement is expansive but valuable when an external earlyhigh strength is required.

Low heat Portland Cement (Type-IV)The lower content of the more rapidly hydrating compounds, C3S and C3A results in a slower development of strength and low heat generation, making the cement of low heat, but the ultimate strength is unaffected low-heat Portland cement was first produced for use in large gravity dams in the United States. Portland blast furnace cement (Type-IS) and Portland Pozzolana Cement (Type-P) can be specified to be of low heat variety.

Pozzolana: is a siliceous or siliceous and aluminous material which by itself possesses little or no cementitious value but is in finely divided form and in the presence of moisture chemically react with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties.


14

Types of Cement


British Classification American Classification

Description BS Description ASTM

Ordinary Portland 12: 1991 Type I C 150-92

Rapid hardening Portland

12:1991 Type III C 150-92

Low heat Portland 1370:1979 Type IV C 150-92

Modified Cement --- Type II C 150-92

Sulphate resisting Portland

4027:1991 Type V C 150-92

Portland blast furnace (slag cement)

146:1991 Type IS C 595-93

Main Types of Portland Cement

815



British Classification American Classification

Description BS Description ASTM

Low heat Portland blast furnace

4246: 1991 -- --

White Portland 12:1989 -- C 150-92

Portland Pozzolana 6588:1985

3892:1993

Type P C 595-93

Main Types of Portland Cement

16

Lecture 01: Introduction To Concrete Technology

Documents

Transcript of Lecture 01: Introduction To Concrete Technology