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Construction Material CEMENT


THE CEMENT Cement is most important material in building construction . The name “cement� refer to the material manufacture from lime stone and clay and made available in powder form, which mixed with water can set to hard durable mass even under water. FUNCTION OF CEMENT : to bind the sand and coarse aggregate together to fill voids in between sand and coarse aggregate particle to form a compact mass by Manish Jain ( www.frontdesk.co.in)


Classification of Cement OPC Ordinary Portland Cement

PPC : Portland Pozzolzna Cement

SRPC : Sulpahte Resisting

Grade 33 窶的S 269-1989 designated as C-33 Grade 43 窶的S 8112-1989 designated as C-43 Grade 53 窶的S 12269-1987 designated as C-53 IS 1489 (Part 1)1991 flyash based IS 1489 (Part 2) 1991 calcined clay-based IS 12330-1988

portland cement

BFSC : Portland blast furnace slag cement

Hydrophobic Cement

IS 455-1989 (PSC) IS 8043-1991

Blended Cement

RHPC : Rapid hardening portland cement

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IS 8041-1990


OPC: Ordinary Portland cement Chemical composition of Portland Cement: a) C3S: Tricalcium Silicate = 3CaO.SiO2 (50%) b) C2S :Dicalcium Silicate = 2CaO.SiO2 ( (25%) c) C3A :Tricalcium Aluminate = 3CaO.Al2O (10%) d) C4AF :Tetracalcium Aluminoferrite = 4CaO. Al2O3.Fe2O3 (10%) e) Gypsum (5%)

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C3S: Tricalcium Silicate ď Ž

Hydrates and hardens rapidly and is largely responsible for initial set and early strength.

ď Ž

Early strength of cement is higher with increased percentages of C3S.

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C2S : Dicalcium Silicate  Hydrates and hardens slowly.  Contributes largely to strength increase at

ages beyond one week.  Responsible for long term strength

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Alite (C3S) and Belite (C2S)

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C3A :Tricalcium Aluminate  Liberates a large amount of heat during the first

few days of hydration and hardening.

 Also contributes slightly to early strength

development.

 Gypsum added to the cement slows down the

hydration rate of C3A.

 Cements with low percentages of C3A are

especially resistant to soils and waters containing sulfates. by Manish Jain ( www.frontdesk.co.in)


C4AF :Tetracalcium Aluminoferrite  Assist in the manufacture of Portland Cement

by allowing lower clinkering temperature.  Also act as a filler  Contributes very little strength of concrete eventhough it hydrates very rapidly.  Also responsible for grey colour of Ordinary Portland Cement

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Hydration of Cement ď Ž In the presence of water the cement compounds

chemically combined with water (hydrate) to form new compounds that are the infrastructure of the hardened cement paste in concrete.

ď Ž Both C3S and C2S hydrate to form calcium

hydroxide and calcium silicate hydrate (CSH). Hydrated cement paste contains 15% to 25% Calcium hydroxide and about 50% calcium silicate hydrate by mass. The strength and other properties of hydrated cement are due primarily to calcium silicate hydrate. by Manish Jain ( www.frontdesk.co.in)


Hydration of Cement ď Ž C3A reacts with water and calcium hydroxide

to form tetracalcium aluminate hydrate.

ď Ž C4AF reacts with water and calcium

hydroxide to form calcium aluminoferrite hydrate.

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Hydration Reactions

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Relative Reactivity of Cement compounds

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Relative volume of major compounds in hydrated cement paste

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CEMENT -MANUFACTURE

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THE CEMENT MANUFACTURING PROCESS dumper loader

Quarry face 1. BLASTING : The raw materials that are used to manufacture cement (mainly limestone and clay) are blasted from the quarry.

2. TRANSPORT : The raw materials are loaded into a dumper.

storage at the plant

crushing conveyor

3. CRUSHING AND TRANSPORTATION : The raw materials, after crushing, are Manish Jain ( www.frontdesk.co.in) transported to the plant byby conveyor. The plant stores the materials before they are homogenized.


THE CEMENT MANUFACTURING PROCESS storage at the plant

Raw mill conveyor

Raw mix

4. RAW GRINDING : The raw materials are very finely ground in order to produce the raw mix.

preheating

kiln cooling clinker 5. BURNING : The raw mix is preheated before it goes into the kiln, which is heated by a flame that can be as hot as 2000 째C. The raw mix burns at 1500 째C producing clinker which, when it leaves the kiln, is rapidly cooled with air So, the raw mix is burnt to produce clinker : the by Manish Jainfans. ( www.frontdesk.co.in) basic material needed to make cement.


THE CEMENT MANUFACTURING PROCESS Gypsum and the secondary additives are added to the clinker. clinker storage

Finish grinding

6.GRINDING : The clinker and the gypsum are very finely ground giving a “pure cement�. Other secondary additives and cementitious materials can also be added to make a blended cement.

silos

dispatch bags

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7. STORAGE, PACKING, DISPATCH :The cement is stored in silos before being dispatched either in bulk or in bags to its final destination.


CEMENT - MANUFACTURE

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Portland Pozzolana Cement (PPC)  This type of cement is most common type

available now in market.  This is made by blending 10-25% reactive pozzolana like flyash or calcined clay with OPC  Addition of pozzolana makes cement sensitive to curing and it requires longer curing than OPC.

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SULPHATE RESISTANT PORTLAND CEMENT ď Ž Sulphate-resisting Portland cement (SRPC) is a

special purpose cement used where sulfates are present in concentrations that would damage Normal Portland cement concrete or mortar. ď Ž Sulfate resistance is achieved by adjustments to chemical composition to limit the level of tricalcium aluminate (C3A) in the SRPC

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SRPC : PROPERTIES  Applied at place where there is exposure to

sulphate such as used in concrete below ground  Higher content of Tetracalcium Aluminoferrite & reducing the Tricalcium aluminate to aluminium  Has darker color than OPC

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SRPC : PROPERTIES  SRPC is made by fusing together a precisely

controlled blend of very finely ground limestone, shale and iron oxide at high temperatures to form cement clinker.  A small quantity of gypsum is added to this clinker before grinding to produce the final fine powder - Sulfate-resisting Portland cement.  SRPC is manufactured in a modern dry process works at Castlemungret, Co.  Limerick and is supplied either in bulk or in bags. by Manish Jain ( www.frontdesk.co.in)


SRPC : ADVANTAGES  Long Term Strength Development  High Strength Concrete  Heat of Hydration  Pure Water and Acid Attack  Sulphate Attack  Alkali Aggregate Reactivity

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Long Term Strength Development ď Ž A significant characteristic of SRPC is the

ability to continue significant strength development beyond the normal 28 day period. ď Ž The benefits of this are obvious, considering that 28 days is a very short period in the life of most concrete structures

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High Strength Concrete  Studies have shown amazing benefits of the

use of SRPC in high performance concrete.  The lower reactivity of the slag makes it easier to control slump in the first two hours that follow mixing,  as well as to reduce the amount of heat developed during hydration at higher cement contents.

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Heat OF Hydration ď Ž Sulphate Resistant Portland Cement have a

much lower heat of hydration than other cements, making them ideal for mass concrete work. ď Ž The lower heat of hydration results in smaller temperature gradients within mass concrete structures, thereby minimising thermal cracking.

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Pure Water and Acid Attack ď Ž The use of SRPC is recommended in

applications where concrete is exposed to pure water and/or acidic conditions. ď Ž Examples are water pipes and reservoirs, soft drink factories and sewage works.

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Sulphate Attack ď Ž SRPC provides higher resistance to sulphate

attack for applications specifically requiring sulphate resistance. ď Ž Applications include sewage works and coastal environments.

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Alkali Aggregate Reactivity ď Ž SRPC has been shown to reduce the risk of

alkali aggregate reaction in concretes containing reactive aggregates.

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BFSC Portland blast furnace slag cement  This type of cement constitutes about 10% of

cement produced in India.  The slag forms 25-60% of the cement.  Every ton of cast iron produce 0.3 tons of furnace slag which can be used in cement industry.  During its setting the Ca(OH)2 liberated by OPC hydration acts as an activator for the slag. by Manish Jain ( www.frontdesk.co.in)


BFSC Portland blast furnace slag cement  Even though it is equated with OPC it

behaves more like PPC and has lower heat of hydration and better sulphate resistance.  At present BFSC produced in India is only Grade-33 and there are proposals to make Grade-43 cements with 45-70% slag content.  BFSC with more than 50% slag has good sulphates resistance

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Hydrophobic cement ď Ž In places of high rainfall and humidity normal

cement tends to set when stored, due to mositure present in the atmosphere. ď Ž By grinding the cement clinker with water repellent film forming substance like oleic acid, a water repellent film is formed around cement particle during manufacturing itself. This prevent setting of cement during storage. ď Ž During mixing with aggregates this film is broken and cement behave as ordinary cement by Manish Jain ( www.frontdesk.co.in)


Blended cement ď Ž For economy a mixture of portland cement,

blast furnace slag and flyash is allowed to be used in some countries. This is known as blended cement. ď Ž In India this type of cement is not produced.

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Rapid Hardening Portland cement (RHPC) ď Ž Rapid Hardening Portland cement (RHPC) is

a special purpose cement used in concrete to ensure a higher rate of early age strength development than that typically achieved using Normal Portland cement (NPC). ď Ž The improved early age strength performance of RHPC is principally achieved through increased product fineness.

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RHPC : PROPERTIES  Similar chemical composition as OPC but

different proportion  Causes to the increased rate of early hardening  Concrete made with RHPC develops in 7 days the same strengths  High early strength is achieved by increasing the CS & CA content

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RHPC : ADVANTAGES  More finely grounded than OPC  Allows formwork to be struck earlier  Providing savings either the quantity of

formwork required in time  Produce heat earlier than OPC, so it can be used in cold weather

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RHPC :Qualities ď Ž RHPC is produced using carefully selected

raw materials. ď Ž Strict quality control throughout each stage of the manufacturing process ensures that a consistent final product is achieved.

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RHPC : Strength  Rapid Hardening Portland cement achieves

higher earlier strengths than OPC because it is more finely ground.  Rapid Hardening Portland cement is chemically similar to OPC and as such concrete mixes should be designed with this in mind.  In particular, optimum ultimate strength of concrete using RHPC will depend, like OPC, on careful attention to the water/cement ratio, consistent with ensuring satisfactory placing and compaction. by Manish Jain ( www.frontdesk.co.in)


PHYSICAL TESTS OF CEMENT Fineness Consistency Soundness Setting Time Compressive Strength Heat of Hydration

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FINENESS OF CEMENT Fineness of cement is a measure of size of particle of cement. It is expressed as specific surface of cement (in sq. cm /gm). IS MEASURE OF FINENESS OF CEMENT IS EXPRESSED AS

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SIZE OF PARTICLE

SPECIFIC SURFACE OF CEMENT


PHYSICAL TESTS OF CEMENT IS 4031 (PART-1 to 11) & I. S. 269 1978. Test for Fineness The first requirement is that 90% of cement should pass IS 90 mircons. Indian standard also specifies fineness test by blaine’s air permeability method as described in IS 40311968  95% of cement particles are smaller than 45 micrometer, with the average particle around 15 micrometer.  Fineness of cement affects heat released and the rate of hydration. by Manish Jain ( www.frontdesk.co.in)


TESTS FOR FINENESS (IS 4031 & I. S. 269 1978. ) The principle is based on relation between the rate of flow of air through a cement bed and surface area of particles comprising the cement bed of given porosity It should be at least 225 m2/kg BLAINE AIR PERMEABILTY APPARATUS

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TESTS FOR FINENESS (I. S. 269 1978. )

BLAINE AIR PERMEABILTY APPARATUS by Manish Jain ( www.frontdesk.co.in)


TESTS FOR FINENESS STEP WISE PROCEDURE 1. Calculate the bulk volume of compacted bed of standard cement

V = (WA-WB) / D

Where

WA= gms of, mercury required to fill the permeability cell WB= gms of mercury required to fill the portion of the cell not occupied by the bed of cement formed by 2.8 gms of standard cement sample . D= Density of mercury at temperature of test. 2. Determine the weight of the standard sample ( W) required to produce a bed having porosity of 0.500 Âą 0.005 (e) as follows:

W = 3.15V(1-e) Where V = Bulk volume of compacted cement powder by Manish Jain ( www.frontdesk.co.in) And e = Desired porosity of bed of cement (0.500 Âą 0.005)


TESTS FOR FINENESS STEP WISE PROCEDURE 3. Determine the time taken by the manometer liquid to fall from second mark from the top to the third mark on the, manometer when air is allowed to permeate through the compacted cement 4. Calculate the constant of the apparatus (k) by using the following formula

Ss = k √ Ts

where k = Ss/ √ Ts

Where Ss is the fineness of standard portland cement in Sq. cm/gm. 5. Using the same quantity (w) of the cement sample find the time (Ts) in seconds required for the manometer liquid fall from second mark to third mark 6. Calculate the specific surface of cement in Sq. cm/gm using the form

S= k √ Ts

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BIS REQUIREMENT FOR FINENESS 1. As per I. S. 269 the residue of cement sampled on the sieve 90 micron after sieving should not exceed .following % by weight for different types of cements.

Ordinary Portland cement Rapid hardening cement Low heat cement

10% 5% 5%

2. As per I. S. 269 the specific surface area of cement sample should not exceed following for different types of cement.

Ordinary Portland cement Rapid hardening cement Low heat cement

2250 sq. cm per gm 3050 sq. cm per gm 3250 sq. cm per gm

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TESTS FOR FINENESS (IS 4031 ) ď Ž More is the fineness

of cement more will be the rate of hydration. ď Ž Thus the fineness accelerates strength development principally during the first seven days

Very large picture of cement

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Test of Normal or standard Consistency (IS 4031) ď Ž Consistency refers to the relative mobility of a freshly

mixed cement paste or mortar or its ability to flow. Normal / standard consistency

Permit vicat’s plunger to penetrate 5 to 7 mm from bottom

Amount of water as % by weight of dry cement by Manish Jain ( www.frontdesk.co.in)


Test of Normal or standard Consistency ( IS 4031) It is the consistency at which the vicat plunger G of 10mm diameter and 50mm length will penetrate 33-35 mm within 3 to 5 minutes of mixing . The test procedure is to carry at least three trial experiment by mixing the cement with distilled water varying from about 24 to 27 % of weight of cement .

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VICAT APPARATUS


Test of Normal or standard Consistency STEPWISE PROCEDURE: (as per I.S.4031-1988) 1. Weigh about 400 gm of cement accurately and placed it in enamel trough . 2. To start with add about 25% of potable water and mix it by means of spatula. Care should be taken that the gauging time is not less than three minutes and not more than 5 minutes. 3. Apply thin layer of oil to inner surface of mould. Fill the Vicat's mould with this paste in the mould resting on non- porous plate. 4. Make the surface of cement paste in level with the top of mould with the trowel. The mould should be slightly shaken to the expel air. 5. Place the mould together with the non-porous plate under the Manish Jain www.frontdesk.co.in) rod bearing the plunger sobythat it (touches the surface of the test block.


Test of Normal or standard Consistency STEPWISE PROCEDURE: (as per I.S.4031-1988) 6. Release quickly the plunger allowing it to sink in the cement paste in the mould. Note down the penetration of the plunger in the paste ,when the penetration of plunger becomes stable in the mould. 7. If the penetration of plunger in the paste is less than the 33 to 35 mm from the top of the mould, prepare the trial paste with increasing percentage of water and repeat the above mentioned procedure until the plunger penetrate to a depth of 33 to 35 mm from the top or 5 to 7 mm from the bottom of mould. 8. Expressed this amount of water as a percentage by weight of dry cement. by Manish Jain ( www.frontdesk.co.in)


Test for Soundness (IS 4031)  Soundness is the ability of a hardened paste to

retain its volume after setting.  The cement is said to be sound when the percentage of free lime and magnesia is with in specified limits .  A cement is said to be unsound (i.e. having lack of soundness) if it is subjected to delayed destructive expansion.  These materials expand in the structure and thus the concrete or mortar also expand, causing unequal expansion of paste by Manish Jain ( www.frontdesk.co.in)


Test for Soundness (IS 4031) The Soundness test is an indication of excess of lime caused by inadequate burning of cement or excess of magnesia or sulphates . 1. Le chatelier’s Test 2. Autocalve test

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Le Chatelier Test STEP WISE PROCEDURE ( AS PER IS : 4031): 1. Prepare a cement paste formed by gauging cement with 0.78 times water required to give a paste of standard consistency. The gauging time should not be less than 3 minutes nor greater than 5 minutes.

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Le Chatelier Test STEPWISE PROCEDURE ( AS PER IS : 4031): 2. Oil the inner surface of the mould. Place the mould on a glass sheet and fill it with cement paste, taking care to keep the edges of the mould gently together. Cover the mould with another piece of glass sheet and peace a small weight on this covering glass sheet and immediately submerge the whole assembly in water at a temperature of 27째Cand keep it for 24 hours. 3. Take out the assembly from water after 24 hrs. Measure the distance between the indicator points and record it (D1) 4. Submerge the mould again in water and bring the water to boiling in 25 to 30 minutes and keep it boiling for three hours. 5. Remove the mould from the water. Allow it to cool and measure the distance between the indicator points and record it ( D2 ). 6. Three samples should be tested and average of the results should be reported. by Manish Jain ( www.frontdesk.co.in)


Le Chatelier Test This test shows unsoundness due to lime only. Unaerated cement paste at normal consistency is first tested for expansion. If the test results does not satisfy requirement of 10mm expansion . Another test shall be made after aeration of cement by spreading of sample to a depth of 75mm at relative humidity of 50% to 80% for 7 days the expansion in this aerated cement test should not be more then 5 mm by Manish Jain ( www.frontdesk.co.in)


Autoclave Test Autocalve Test is used for both lime and magnesia excess indication . All the cement having a magnesia content more then 3 % is to be tested for soundness by this test with unaerated cement . The test consist of heating bar made of cement paste with water of normal consistency and measuring its expansion

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Test for Setting Time The Setting Time is also determined by vicat’s needle on cement paste of normal consistency . For this test , we use 1mm square needle , this time to penetrate 3335mm is taken as initial setting time. For final setting time we use special needle (5mm dia) and time at which this needle will not penetrate more then 0.5mm is taken as final set.

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Compressive Strength This is most important test. The compressive strength of cement is determine from cube of face 50cm2 in area made of cement mortar with one part cement and three part of standard sand (conforming to IS 650-1966) by weight and water corresponding to 25% normal consistency plus three percent of combined weight of cement and sand .

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Heat of Hydration (IS 4031-1968) Hydration of cement is chemical reaction and it produce heat . In very massive construction this effect can rise the temperature of concrete as much as 50째C . In such cases , we should use low heat cements or adopt cooling method. The test is carried out by calorimeter. Low heat cement should satisfy following criteria 1. In 7 days, heat generated should not be more than 65 calories/gm of cement. 2. In 28 days, heat generated should not be more than 75 calories/gm of cement. by Manish Jain ( www.frontdesk.co.in)


Cont. on Heat of Hydration ď Ž Cements do not

generate heat at constant rate as illustrated in Figure for a typical Portland cement

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Storage of Cement  Cement is moisture-sensitive material; if kept

dry it will retain its quality indefinitely.

 When exposed to moisture, cement will set

more slowly and will have less strength compared to cement that kept dry.

 At the time of use cement should be free-

flowing and free of lumps.

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Storage of Cement

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Construction material cement  

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