Cement, Mortar and Concrete

Building material Civil engineering

Admixture used in Concrete
Bogues Compound
Properties of Cement
Ordinary Portland cement OPC:
Portland Pozzolana cement PPC:
Rapid Hardening Cement RPC
Amount of Water content used during Test on Cement
Note
High Alumina Cement HAC
Lime-Cement Mortar
Mortar
mortar after it has set
Polymer concrete:
Strength of concrete
Minimum Number of concrete sample
Durability
Fly ash
Workability of Concrete based on Tests
Ferro-Cement
Surkhi

Air-entraining admixture

These are the type of admixtures that entrapped million of an air bubble in between the voids of the aggregate, which act as the flexible wall bearing that slips pass over each other thereby modified the properties of concrete with respect to workability, frost action, segregation, bleeding.

Example:

Natural wood resin, plant and animal fatty oil, stearic acid, oleic acid, hydrogen peroxide, aluminium powder

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The setting and hardening of cement after addition of water is due to hydration of some of the constituent compounds of cement such as Tricalcium aluminate, Tricalcium silicate, Di-calcium silicate, and Tetra calcium alumino-ferrite.
These compounds are known as Bogue’s Compounds.
Major compounds of cement clinker (also known as Bogues compounds) are:
Bogues compounds and its Properties

Tetra-calcium alumino-ferrite(C4AF)

Formed within 24 hours of the addition of water.
The High heat of hydration in initial periods.
This is called as Felite.
The heat of hydration is 420 J/gm.
It has the poorest cementing value but it responsible for long term gain of strength of the cement.
The rate of hydration is highest for C4AF

Tricalcium aluminates(C3A)

Formed in 24 hours of the addition of water.
Max. evolution of heat of hydration.
Reduce the setting time of cement.
Celite is the quickest one to react when the water is added to the cement.
It is responsible for the flash setting.
The increase of this content will help in the manufacture of Quick Setting Cement.
The heat of hydration is 865 J/gm.
heat of hydration is highest for C3A.
Celite is the quickest one to react when the water is added to the cement.
It is responsible for the flash setting.
It provides weak resistance against sulphate attack and contribution to the development of strength.

Di-calcium silicate(C2S)

Last compound formed during the hydration of cement
Responsible for progressive later stage strength
The Proportion of this increase in hydraulic structures, bridges, etc.
This compound will undergo reaction slowly.
It is responsible for the progressive strength of concrete.
This is also called as Belite.
The heat of hydration is 260 J/gm.
This compound will undergo reaction slowly
A higher percentage of C2S results in slow hardening, less heat of hydration, and great resistance to chemical attack.

Tri-calcium silicate(C3S)

Formed within a week.
Responsible for initial strength of cement.
Contribute about 50-60% in cement.
This is also called as Alite.
This is also responsible for the initial set and early strength of the concrete.
The cement that has more C3S content is good for cold weather concreting.
The heat of hydration is 500 J/gm.
It undergoes hydration within one week.
It has the best cementitious property among all the other Bogue's Compounds.
Tricalcium Silicate (C3S) hardens rapidly
The cement that has more C3S content is good for cold weather concreting.

Chemical Name	Formula	Notation	Percentage
Tricalcium Silicate	3CaO, SiO2	C3S	30-50
Dicalcium Silicate	2CaO, SiO2	C2S	20-45
Tricalcium Aluminate	3CaO, Al2O3	C3A	8-12
Tetra-calcium Alumino-ferrite	4CaO, Al2O3, Fe2O3	C4AF	6-10

Note

The decreasing order of rate of hydration of Portland cement compounds is

C4 AF &gt; C3 A &gt; C3 S &gt; C2 S.

Decreasing order of heat of hydration of Portland cement is

C3 A &gt; C3 S &gt; C4 AF &gt; C2S

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Following are parameters and properties of cement:

1. Bulk density of cement = 1440 kg/m3

2. Specific gravity of cement = 3.15

3. Weight of one bag of cement = 50 kg

4. Volume of cement bag = 50/1440 = 0.035 m3

5. Number of cement bags in 1 m3 = 30 approx.

6. Volume of dry mortar is 30% more than volume of wet mortar.

∴ Volume of dry mortar = 1.3 × volume of wet mortar

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Cement can be defined as the bonding material having cohesive &amp; adhesive properties which makes it capable to unite the different construction materials and form the compacted assembly. Ordinary/Normal Portland cement is one of the most widely used types of Portland Cement. The name Portland cement was given by Joseph Aspdin in 1824 due to its similarity in color and its quality when it hardens like Portland stone. Portland stone is white grey limestone on the island of Portland, Dorset.

Low heat Portland cement:

Low C 3 S and C 3 A and more contents of C 2 S
It is use in mass concrete work
Rate of development of strength is low but ultimate strength is same

Super Sulphated Portland cement :

80–85% Granulated slag + 10– 15% calcium sulphate + 5% Portland cement clinker.
It is resistant to chemical attacks particularly tosulphate & highly resistant to sea water
It should not be used with any admixture

Portland Slag cement:

The mixture of portland cement,granulated blast furnace slag & Gypsum
High Sulphate resistance & it is Used in mass concreting work

Quick setting cement:

Fine grounded OPC with reduced Gypsum content & small amount of aluminium sulphate.
IST = 5 minutes & FST = 30 minutes
Used in under water concreting.

White and Coloured Portland cement (IS: 8042) :

From Pure white chalk, china clay & Iron Oxide should not bemore than 1%.
These are used for making Terrazzo flooring, ornamental works & casting stones.
Hunter scale is use for checking the whiteness of cements
5–10% Colouring pigment before grinding

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This cement is produced by inter grinding the cement clinkers with 10 - 15 % of pozzolanic material.
Pozzolanic material is essentially a siliceous compound that is itself does 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.

Effects of pozzolana in ordinary Portland cement

Higher water tightness
Low heat of hydration
Reduces the cost
Higher resistance against chemical attacks (Chloride &amp; Sulphate)
Higher resistance against volume change
A slower rate of gain of strength
Increases shrinkage
Reduces permeability
Reduces bleeding

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It is obtained by grinding 10% more than the OPC for greater Fineness.
The difference of rapid hardening cement to that of ordinary Portland cement is the quantity of Limestone (tri-calcium silicate) used as raw material, which gives the high early strength to the cement.
It attains early strength due to larger proportion of lime grounded finer than normal cement.

Properties of Rapid Hardening Cement:

1. It gains strength faster than OPC. In 3 days it develops 7 days strength of OPC with same water cement ratio.
2. Its initial setting times is 30 mins and final setting time is 600 mins which is same as OPC.
3. It emits more heat during setting, therefore this cement is unsuitable for mass concreting.
4. This cement is lighter and costlier than OPC. Its short curing period makes it economical.
5. This cement should be stored in a dry place, or else its quality deteriorates due to premature carbonation and hydration.

LIST OF IS:CODES RELATED TO CIVIL ENGINEERING STUDY AND CEMENT

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Type of test water content

Initial and Final Setting Time 0.85p

Compressive Strength p/4 + 3

Tensile Strength p/5 + 2.5

Soundness Test 0.78p

Note Where p = Standard consistency

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Autoclave test is used to determine unsoundness due to magnesia.
Vicat apparatus is used to determine the consistency of cement.
Le Chatelier's flask is used to determine the specific gravity of cement.
Le Chatelier's apparatus is used to determine the unsoundness due to lime.
Sieve test and Blainis air permeability apparatus is used to determine the fineness of the cement.
Low heat cement sets slower than OPC.
Final setting time does not decide the strength of cement.
Initial setting time of Portland PozzoIlona is 30 minutes.
Air-induced setting is observed when stored under damp conditions.
Calcium sulphate (CaSO4): this ingredient is in the form of gypsum and its function is to increase the initial setting time of cement.

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IT is a special cement, manufactured by mixing of bauxite (Aluminum ore) and lime (Limestone) at a certain temperature.
The setting time of high alumina cement is greatly affected by the addition of plaster of Paris, lime, Portland cement, and organic matter. Thus, no additives should be used.
High alumina cement is very reactive and has very high compressive strength.
As per IS Code: 6452:1989, the maximum initial and final setting time for high alumina cement is same as ordinary cement.
Due to the property of the cement, in actual the alumina cement has higher initial setting time but lower final setting time as compared to ordinary cement.

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In this type of mortar, lime is used as binding material.
The lime may be fat lime or hydraulic lime.
The fat lime shrinks to a great extent and hence it requires about 2 to 3 times its volume of sand. The lime should be slaked before use. This mortar is unsuitable for water logged areas or in damp situations.
For hydraulic lime, the proportions of lime to sand by volume is about 1:2 or so. This mortar should be consumed within one hour after mixing. It possesses more strength and can be used in damp situations.
The lime mortar has high plasticity and it can be placed easily.
It possesses good cohesiveness with other surfaces and shrinks very little.
So, lime mortar gives a fairly strong surface finish.
It is sufficiently durable, but it hardens slowly.
It is generally used for lightly loaded above-ground parts of buildings.
Also known as Gauged mortar.
It is made from cement and lime.
The advantages of lime-cement mortar are increased Water retentivity, workability, bonding properties and frost resistance.
This mortar gives good and smooth plaster finish and is used in buildings.

Mix proportions are given below-

Location Ratio (by volume) (Cement : Lime : Sand)

Outside walls 1 : 1 : 6 to 1 : 2 : 9
Inside walls 1 : 2 : 9 to 1 : 3 : 12

Note:-

Since presence of lime increases the water retentivity in cement. This presence of water reduces the shrinkage of cement upon drying.

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The term mortar is used to indicate a paste prepared by adding the required quantity of water to a mixture of binding material like cement or lime and fine aggregate like sand.

Types of mortar depending on binding material are:

1. Lime mortar
2. Cement mortar
3. Gauged mortar
4. Surkhi mortar
5. Gypsum mortar

The requirement of a mortar before it has set:

It should remain usable for 2 hrs after mixing
It should be sufficiently cohesive to stay on a trowel.
It should be sufficiently workable to spread easily.

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It should be strong enough to carry the loads that are applied to it by the masonry units.
It should be capable of resisting the penetration of rainwater.
It should be capable of resisting the penetration of rainwater.
It should not affect the durability of the materials with which it comes into contact.
The joints formed by mortar should not develop cracks and they should be able to maintain their appearance for a sufficiently long period

Note:

The lime mortar should be consumed within 36 hours after its preparation and it should be kept wet or damp.
The cement mortar should be consumed within 30 minutes after adding water and for this reason, it is advisable to prepare cement mortar of one bag of cement at a time.
The gauged mortar or composite mortar should be used within 2 hours of the addition of cement.

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Polymer concrete is a composite material in which the aggregate is bound together in a matrix with a polymer binder. The composites do not contain a hydrated cement phase, although Portland cement can be used as an aggregate or filler.The impregnation of monomer and subsequent polymerisation greatly improves some properties of the concrete.

Properties:

a.High tensile, flexural, and compressive strengths
b.Resistance to oil, grease, abrasion and good adhesion to most surfaces
c.Good long-term durability with respect to cycles of freezing and thawing
d.Low permeability to water and aggressive solutions
e.Light weight.

Applications:

a.Most suitable for sewage disposal works because of its high sulphate and acid resistance properties.
b.In the production of prefabricated elements and prestressed concrete.
c.In ferro-cement products and marine works.
d.In nuclear power plants and industrial applications.

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*Strength of concrete is generally tested after 28 days as concrete cube strength because concrete gains strength with time after casting. It takes much time for concrete to gain 100 % strength and the time for the same is still unknown. The rate of gain of concrete compressive strength is higher during the first 28 days of casting and then it slows down.

The below table shows the concrete compressive strength with age:

Age Strength (Percent)

1 day 16 %
3 days 40 %
7 days 65 %
14 days 90 %
28 days 99 %

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As per IS 456:2000, cl. 15.2.2, The minimum numbers of samples required for testing depending upon the quantity of concrete in the work is given below –

No of concrete sample
Quantity of concrete in the work, m3	Number of samples
1 – 5	1
6 – 15	2
16 – 30	3
31 – 50	4
51 and above	4 plus one addition sample for each additional 50 m3

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Durability is defined as the capability of concrete to resist weathering action, chemical attack and abrasion while maintaining its desired engineering properties.

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i) Cement content and water-cement ratio of concrete
ii) Cover to embedded steel
iii) Shape and size of member
iv) The Environment
v) Type and Quality of constituent materials

LIST OF IS:CODES RELATED TO CEMENT IN CIVIL ENGINEERING

Cement content:

Mix must be designed to ensure cohesion and prevent segregation and bleeding. If cement is reduced, then at fixed w/c ratio the workability will be reduced leading to inadequate compaction. However, if water is added to improve workability, water / cement ratio increases and resulting in highly permeable material.

If excess cement content is used, problems like drying shrinkage, alkali-silica reaction may occur which finally effects the durability of concrete.

Curing:

It is very important to permit proper strength development aid moisture retention and to ensure hydration process occur completely.

Permeability:

It is considered the most important factor for durability. It can be noticed that higher permeability is usually caused by higher porosity. Therefore, a proper curing, sufficient cement, proper compaction and suitable concrete cover could provide a low permeability concrete.

Concrete

Concrete is a composite material that is a mixture of binding materials, coarse aggregate, fine aggregate, water, and admixtures.

Cement imparts adhesive and cohesive properties to the concrete and binds various ingredients into a compact mass.

Coarse aggregate occupies the bulk of the volume of concrete and contributes to its strength.

Fine aggregate act as a filler material and helps in improving the workability of concrete.
Water causes hydration of the cement.

Admixtures are the material that is added to the concrete to give it certain desired characteristics.

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Definition

Ash produced in small dark flecks by the burning of powdered coal or other materials and carried into the air.

Properties

Fly ash is a pozzolanic material that is used as a replacement of cement.
It also acts as a replacement of sand, when the sand in concrete is replaced by 10% of fly ash the concrete strength increases and thus makes concrete economical. Although if fly ash is increased beyond 10% then the overall strength of concrete decreases.
Fly ash as a replacement of cement provides later strength to concrete.
Initially pozzolana does not have cementious property, but when it reacts with calcium hydroxide(generated by hydrating cement) it acts as a cementitious material. Thus the early age strength provided by pozzolanic material (fly ash) cement is very less.

Range

15% - 30%

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**Workability of Concrete based on Tests**
Work Description	Slump (mm)	Compaction Factor	Vee-Bee time
Moist Earth	-	-	40 to 25-20
Very Dry	-	.70	20 to 15-10
Dry	0 - 25	.75	10 to 7 - 5
Plastic	25 - 50	.85 - 90	5 to 4 -3
Semi Fluid	75 - 100	.90 - .95	3 to 2-1
Fluid	100 - 150	.95 - 100	less than1

**Slump Test**
Degree of Workability	Slump value in mm
Very low	Less than 25
low	25-75
medium	50-100
high	75-100
very high'	100 – 150

Degree of workability	Slump mm	Compacting factor
Degree of workability	Slump mm	Small apparatus	Large apparatus
Very low compacting factor is suitable	-	0.78	0.80
Low	25 – 75	0.85	0.87
Medium	50 – 100	0.92	0.935
High	100 – 150	0.95	0.96
Very High	-	-	-

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Ferroecement developed by P.L. Nervi, an Italian architect, and engineer, in 1940. It consists of closely spaced wire meshes which are impregnated with rich cement mortar mix.
The wire mesh is usually of 0.5 to 1.0 mm diameter wire at 5 mm to 10 mm spacing and cement mortar is of the cement-sand ratio of 1: 2 or 1: 3 with water/cement ratio of 0.4 to 0.45.
The ferrocement elements are usually of the order of 2 to 3 cm in thickness with 2 to 3 mm external cover to the reinforcement. The steel content varies between 300 kg to 500 kg per cubic meter of mortar.
The basic idea behind this material is that concrete can undergo large strains in the neighbourhood of the reinforcement and the magnitude of strains depends on the distribution and subdivision of reinforcement throughout the mass of concrete.
It is impervious in nature, has the capacity to resist shock and no formwork is required to gain initial strength.
The main advantages are the simplicity of its construction, a lesser dead weight of the elements due to their small thickness, its high tensile strength, fewer crack widths compared to conventional concrete, easy repairability, noncorrosive nature and easier mouldability to any required shape.

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Surkhi is broken brick powder or burnt clay soil and used as a substitute for sand for concrete and mortar, and has almost the same function as of sand but it also imparts some strength and hydraulicity.

Surkhi is used as a substitute for sand for concrete and mortar, and has almost the same function as of sand but it also imparts some strength and hydraulicity. Surkhi is made by grinding to powder burnt bricks, brick-bats or burnt clay ; under-burnt or over-burnt bricks should not be used, nor bricks containing high proportion of sand. When clay is especially burnt for making into surkhi, an addition of 10 to 20 per cent of quick lime will improve its quality ; small clay balls are made for burning.

Table of Contents

Cement, Mortar and Concrete

Building material Civil engineering

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Admixture

Type of admixtures:

Example:

Example:

Retarders

Example:

Accelerators

Example:

Air-entraining admixture

Example:

Tetra-calcium alumino-ferrite(C4AF)

Tricalcium aluminates(C3A)

Di-calcium silicate(C2S)

Tri-calcium silicate(C3S)

Note

Properties of Cement

Ordinary Portland cement OPC:

Low heat Portland cement:

Super Sulphated Portland cement :

Portland Slag cement:

Quick setting cement:

White and Coloured Portland cement (IS: 8042) :

Portland Pozzolana cement PPC:

Effects of pozzolana in ordinary Portland cement

Rapid Hardening Cement RPC

Properties of Rapid Hardening Cement:

Type of test water content

High alumina cement (HAC)

Lime-Cement Mortar:

Mix proportions are given below-

Location Ratio (by volume) (Cement : Lime : Sand)

Mortar

Types of mortar depending on binding material are:

The requirement of a mortar before it has set:

*The requirement of a mortar after it has set:

Note:

Polymer concrete:

Properties:

Applications:

Strength of concrete

The below table shows the concrete compressive strength with age:

Age Strength (Percent)

*Minimum Number of concrete sample

*Durability

As per IS 456:2000, the factors influencing the durability of concrete are:

Cement content:

Curing:

Permeability:

Concrete

Definition

Properties

Range

*Workability of Concrete based on Tests

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