Summary

• Vital construction material

• The Mixture of Portland cement, water, aggregates and in some cases, admixtures.

• The cement and water form a paste that hardens and bonds the aggregates together.

Concrete is one of the most commonly used building materials.

Concrete is a versatile material that can easily be mixed to meet a variety of special needs and formed to virtually any shape.

Ingredients of concrete

Cement

Sand

Coarse aggregate

Fine Aggregate

Water

Method of mixing of Concrete

Hand mixing

Machine mixing

Main Ingredients of concrete

HAND MIXING

• For small & important works mixing of concrete is done by hand.

• Hand mixing of concrete should be done on hard,clean,water tight surface like a concrete floor or metal tray.

• It requires about 10% more of cement than what is required in Machine mixing.

MACHINE MIXING• For large scale work concrete mixers are used.

• The interval of time for which the concrete should be mixed depends upon the quantity of mixer.

• Time ranges from 1.5 to 3 min.

• Types ofconcrete mixer:-1)Rotary mixer 2)Tilting mixer

Types Of Grade Mix Portion (Cement : Sand : Corse aggregate)

M5 1 : 5 :10

M7.5 1 : 4 : 8

M10 1 : 3 : 6

M15 1 : 2 : 4

M20 1 : 1.5 : 3

M25 1 : 1 : 2

M refers to the Mix and the number indicates the specified compressive strength of that Mix at 28 days expressed in N/mm^2

Classification Of Cement

According To Binding Material

Cement Concrete

Lime Concrete

According To Design of Concrete

Plain Cement Concrete(PCC)

Reinforced Cement

concrete(RCC)

• The process of keeping concrete wet to enable

it to attain full strength is known as curing.

• The objective of curing is to prevent loss of

moisture from concrete due to evaporation or

because of any other reasons.

• Curing should be done for a period of three

weeks but not less then 10 days.

• To do curing, any one of the following method can be used.

i. The surface of concrete is coated with a layer of bitumen or similar other waterproofing compound which gets into the pores of concrete and prevent loss of water from concrete.

ii. Concrete surface is covered with waterproof paper or with a layer of wet sand. It could also be covered with gunny bags.

ADVANTAGES

• High compressive strength

• More economical than steel

• Not subjected to corrosive wreathing

• Versatile material in building construction

• Hard and durable

• Water tightness & strength

DISADVANTAGES

• Poor tensile strength

• Develops shrinkage stresses

• Requires skill and supervision

• Cracks may occur & strength of concrete may come down

• Repairing is difficult

• Curing time of concrete is more

• Sand is an important building material. IT CONSISTS OF

SMALL ROUNDED OR ANGULAR GRAINS OF SILICA

sio2 AND IS FORMED BY THE DECOMPOSITION OR

DISINTEGRATION OF SAND STONE UNDER THE

ACTION OF WEATHER SUCH AS WIND,RAINS FORST

ETC.

• It forms a major ingredient in concrete , lime mortar ,

cement mortar etc.

• It abundantly occurs in nature.

• Sand is formed by weathering of rocks

• Sand can be divided into three main class

depending upon the source from it is obtained

• 1)pit sand

• 2)river sand

• 3)sea sand

• It is obtained by digging pits in the soil. It is excavated

from A depth of about 1.2 M from the ground level.

• This soil consists of sharp angular grains, which are free

from silt, clay, salts etc.

• Clean pit sand forms an excellent material for mortars

and concrete.

• This sand is widely used for all purposes, it is considered

to be best sand suitable for important works

• It is obtained from the banks or beds of rivers and it

consists of fine rounded grains.

• The river sand is available in clean conditions and is

almost white in color.

• Sea sand is obtained from the sea shores. It is also

clean having rounded particles.

• Sea sand is light brown in color. Sea sand is always

available in combination with certain injurious salts and

hence sea sand is unsuitable for making mortar or

concrete.

• Sea sand increases the setting time of cement.

• Hence, it is the general rule to avoid use of sea sand for

engineering purposes.

• According to the particle size the sand can be classified as coarse

sand, medium sand and fine sand

• 1)coarse sand:

• Sand particle passing through 3.175 mm SIEVE IS TERMED AS

COARSE SAND. It is generally used for masonry work.

• 2)medium sand

• Sand particle passing through 2.36 mm SIEVE WILL BE CALLED

MEDIUM SAND. It is used for plastering.

• 3)fine sand

• Sand particle passing through 1.5875 mm SIEVE WILL BE

CALLED FINE SAND. It is used for plastering.

• Good sand should possess the follwing

characterisitics

• It should be chemically inert

• It should have sharp angular grains

• The size of grains should be between 4mm and 6mm

• It should be strong and durable

• It should be not conain salts wich attract moisture from

the atmosphere

• Following are the various uses of sand

• It is used for making lime mortar

• It is used for making cement mortar

• It is used for making cement mortar

• It is used for making cement concrete

• It is used for masonry work , plastering and pointing

works

• Aggregate: – Granular material of

mineral composition such as sand, gravel, shale, slag or crushed stone.

• Coarse Aggregate:– Predominantly

retained on the 4.75mm (#4) sieve

Fine Aggregate: Completely passing through

the 9.5mm (3/8”) sieve

• Bedrock

– Igneous (solidification of

molten material

– Sedimentary (consolidated

transported material)

– Metamorphic (preexisting

rock changed by

temperature or pressure

over time)

• Mantle

– Material that covers

the bedrock which

may be cm or km in

thickness

– Boulders, cobbles,

gravel, sand, silt, clay

• Crystal Structure

• Optical Properties

• Hardness

• Color

• React with Acids

• Luster (dull, glassy)

• Fracture

• Group I –Glassy– Quartz, Obsidian

• Group II – Dull, Fine Grain– Scratch with a knife

• Shale, limestone

– Hard - Chert, Basalt

• Group III - Granular– Scratch with a knife

• Limestone, dolomite

– Hard • Granite, Gabbro

Topaz - 8

Corundum - 9

Diamond - 10

glass

Orthoclase - 6

file

Quartz, Chert - 7

Calcite - 3

Dolomite - 4

Apatite - 5

knife

Talc - 1

fingernail

Gypsum - 2

penny

Hardness

Mohs Hardness

Carbonates

Calcite

Powdered Dolomite

Non-Carbonates

HCl Reactivity

0.1N HCl

Double Plane

Feldspars

Single Plane

Mica, etc.

Planer

Fracture

Concave Surface

quartz, chert

Conchoidal

Fracture

Cleavage

Field Tests

• Voids (internal, external, interparticle)

Oven DrySurface Saturated

Dry

Wet

Moisture Content

• Normal-weight (ASTM C33)

– Gravel,

– Crushed stone

– Natural sand

– Manufactured sand

– Bulk Specific Gravity = 2.40 - 2.90

• Lightweight (ASTM C330)

– Pumice,

– Expanded shale and Clay

– 3M microspheres, cenospheres...

– Uses: filler or low modulus applications

• Geo Fills, Structural Slabs

Good adhesion with brick,stones etc.

Resist penetration of rain water.

Should be cheap, durable and workable.

Should be set quickly

Joints formed by mortar should not develop

cracks

Maintain their appearance for long period

•As per binding material:-

•Cement Mortar

•Lime Mortar

•Gauged Mortar

•Gypsum Mortar

•Surkhi Mortar

•As per Nature of application:-

•As per Density of the Mortar

•Special mortar

Uses of MORTAR

•Bind bricks or stone

•Used in plaster work as finishing material.

• Joints covered by plaster work.

• Bituminous binders used in pavement construction works includes both bitumen and tar.

• The bitumen is a binding material which is present in asphalt. It is also sometimes called the mineral tar.

• Bitumen is a petroleum product obtained by the distillation of petroleum crude whereas road tar is obtained by the destructure distillation of coal or wood.

• It is chemically hydrocarbon.

• The bitumen is black in colour and it is obtain in solid or semisolid state.

• Bituminous material are used for various engineering purposes such as dam roof courses,water proff layer for tanks etc.

• they are very commonly used in highway constructions n pavements

• Bitumen is available in variaties of types n grates. Thus

bitumen material is classified as bellow:

• It is defined as a natural or artificial mixture in which bitumen is associated with inert mineral matter

• it is black or brownish black in color.ASPHALT:

• it is also one off the most important bituminous material which is produced by destructive distillation of organic material such as coal, oil, peat, and wood.

• It is black to dark brown in color.

TAR:

• For cold application as in case of repairing cracks in roofs, floors etc. asphalt mixed with the liquid solvent and then it is called cut black asphalt.

• It is obtained by fluxing asphaticbitumen in presence of some suitable liquid distillates of cold tar or petroleum.

CUT BLACK:

• For cold application asphalt is available in the form of emulsion.

• it is the liquid product containing bitumen to a great extend in an aqueous medium.EMULSION:

• The bituminous material are also called binders

which are used in combination with mineral

aggregate in road construction. Their functions

are as follows:

1. BINDING EFFECTS: the bitumen binds the

surface particles together.

2. CUSHION: it acts as a cushioning material on

the surface absorbs impact friction etc due to

movements of vehicles on road.

3. SEALING OF SURFACE: When used with the

dense graded and angular material. It seals the

surface of the road against ingress of water.

4. RESISTANCE TO WEATHERING AGENTS: If

the bituminous material is selected properly

and is used in road construction can resists

effectively the actions of weathering agents like

the wind and the sun.

1. the viscosity of the bitumen at the time of

mixing and compaction should be adequate.

2. It should posses sufficient adhesion with the

aggregate in the mix in presence of water.

3. The presence of water the bitumen should not

strip off from the aggregate.

4. The bituminous material should not be highly

temperature susceptible.

• Book:-

– Elements of CIVIL Engineering

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