Mixing of concrete.pptx

WEL-COME

THE MS UNIVERSITY OF BARODAPOLYTECHNIC

SECOND SEM., S.Y.D.CIVILROLL NO: 34 TO 44

CIVIL ENGINEERING DEPARTMENT

TOPICS:1. WHAT IS CONCRETE2. INGRADIENTS OF CONCRETE3. VARIOUS TYPES OF CONCRETE4. PROPOSTIONING OF CONCRETE5. BATCHING OF CONCRETE6. WATER CEMENT RATIO7. MIXING OF CONCRETE8. SLUMP TEST9. WORKABILITY

It is simply defined as the mixture of cement , fine aggregates , coarse aggregates , water , admixtures

Concrete used on worked is specified according to IS 456(2000) .

It is one of the very important and widely used material in construction .

concrete = binder + fillers

Cement , water,

admixture

Fine aggregates and coarse aggregates

(which occupies around 60%)

CONCRETE

INGREDIENT

cementIf fills up voids existing in fine aggregates.It provides strength and binding properties to the concrete mixture.

Fine aggregate

The particles which passes from IS sieve 4.75 mm & should be retained from 75 micron is known as fine aggregates.It should not contain any organic material.The main function of fine aggregate is to fill-up voids existing in coarse aggregates.

Coarse aggregate

The particles which are retained through IS sieve 4.75 is known as coarse aggregates.Coarse aggregates should be hard & strong to give enough strength and durability to concrete.

INGREDIENTWater

Water acts as a lubricant for the aggregates and gives workability to the concrete.The quality of concrete depends on the quality and quantity of the water added.

AdmixtureAdmixtures or additives as required by situation, ingredients added to concrete or mortar modifies its properties immediately before or after mixing.

Admixtures1. Chemical admixture (for specific property i.e. performance &

enhancement)2. mineral admixture (for improvement of long – term strength &

durability) others : Air entraining admixtures. High range of water reduces or super plasticizers. Normal range of water reducers or plasticizers &

retarders.

Types of concrete

According to design of concrete:

P.C.C. (Plain cement concrete) R.C.C. (Reinforcement cement concrete) B.B.C.C. (Brick bats cement concrete) B.B.L.C (Brick bats lime concrete)

According to grade it is defined as:

The grade of concrete is specified by its 28 Day’s cube strength ( e.g. M20 means the cube strength is 20 N/sq. mm)

M7.5 1:4:8M10 1:3:6M15 1:4:8M20 1:1.5:3M25 1:1:2

PROPORTIONING OF CONCRETE

Methods By designing the concrete mix. By adopting nominal mix. Arbitrary method. Fineness modulus of method. Maximum density method. Maximum voids method. w/c ratio method (water cement ratio).

• Batching is the process of measurement of specified quantity of ingredient in correct proportion batching is done by two process.

1. By volume batching :• Batching by volume means measuring

ingredient of concrete by its volume.2 . By weigh batching :• Batching is done according to the weight

of ingredients. It is more preferable method to volume batching.

BATCHING OF CONCRETE

Batching

The equipment falls into three categories in both batching process as follow:

1. Manual batching 2. Semi-automatic batching3. Fully-automatic batching

Volume batchingBatching by volume means the measurement of ingredients is

done by volume. Generally cement is measured by weight or number of bags. Batching of aggregate should be done with the Forma or

Cage Box Batching of water is done with the help of calibrated canes &

the measuring accuracy should be within 1%. Batching of admixture should be done as same accuracy for

cement (mineral admixture) and water (chemical admixture).

For e.g. proportion (1:2:4) i.e. 1 part of cement 2 part of sand 3 part of coarse aggregates

weigh batching

Batching is done by the weight of ingredient. It is more preferable than volume batching. It is more accurate & needs more uniform proportioning.

For the process of hydration dry mix of ingredients , the water is added.

The water make the concrete mix workable.

According to Abram’s w/c law , lesser the w/c ratio in a workable mix , greater will be the strength.

The lower water content will produce stiff paste having greater binding strength will be increase.

Higher water will increase the workability but decrease the strength of the concrete mix.

Generally a minimum w/c ratio is taken 0.3 by weight.Typical values are 0.4 to 0.6 .

w/c ratio=water

cement

Water-cement ratio

Water cement ratio

Concrete ratio quantity Water1:3:6 34 litre1:2:4 30 litre1:1.5:3 27 litre1:1:2 25 litre

For different ratio of concrete the amount of water for 50 kg of cement is as below:

Mixing of the concrete

For producing the homogeneous mass of concrete , the ingredient are mixed . Depending upon the requirement , quality , quantity , etc, the method of mixing is decided.

Generally there are two methods for mixing the concrete ,

o 1. hand mixing : by manual labors Small workso 2 . Machine mixing :• For big works where requirement is continuous• Mixed automatically in batching plants

Hand mixing In this type , the mixing is done by manual

labors. This method is adopted for small construction

works . Requirement of cement is more than machine

mixing (10%). Normally the mixing time is about 3 minutes.

Hand mixing procedure

Construction of platform of bricks , lean concrete or iron-sheet.

Spread-out sand evenly , spread cement on it. Mix it till the color of mixing become uniform. Spread this mixture & spread coarse admixture

then mix it. During mix it remaining water should be added

with continuation process. Time for mix is generally 2 to 3 minutes.

Hand mixing

Machine mixing This is similar to hand mixing only the mixing is

carried out in a rotating drum

Machine mixing

For machine mixing , all the ingredients of concrete including water are collected in a revolving drum and then the drum is rotated for a certain period.

Machine mixing

Machine mixing Types of machine mixing1. Manual mixer2. Electrical mixer3. Fuel mixer

R M C( Ready Mix Concrete )

Ready – mix concrete is type of concrete that is manufactured in a factory or batching plant , according to design and then delivered to a work site , by transit truck.

RMC is bought and sold by volume. The truck carries a mix in a revolving chamber

which like the concrete mixer . It prevents the segregation of concrete .

RMC( Ready Mix Concrete )

It is manufactured under computer-controlled operations and transported and placed at the site of constructed.

RMC( Ready Mix Concrete )

Advantages of ready mix

concrete Better quality concrete is produced. storage space for basic materials at site is not

required . Wastage of basic materials are avoided.

Workability It is desirable that freshly mixed concrete be

relatively easy to transport , place , compact and finish without harmful segregation.

A concrete mix satisfying these condition is said to be workable.

Use of aggregates which are round and have smooth surface increases the workability.

Slump Test This test is performed for getting rough idea of workability. Procedure: Place frustum on the base plate. Fill the wet concrete mixture in the cone in three equal

layers. Compact each layer 25 times using compacting steel rod and

the top surface is struck off by means of a sawing and rolling motion of the temping rod.

The cone is slowly lifted and observed the slump. Invert the frustum and place it close to the collapsed

concrete. Measure and record the slump and type of slump. The slum can be measure as shown in figure.

Slump test

Slump test Results: There are three types of slump that can

happen which are: True slump Shear slump Collapsed slump as shown in the below figure.

Slump test

Group members

Jadav KeyurJangid Rinku Joshi Parth

Kachipulav IshtiyaqKachot NileshKadam KaranKadu Mayur

Katariya KiranKharva Nehal Kharva Jaina

We are thankful to….

All respected lecturers and all supported members for preparation of this presentation…

Special thank to, Lafarge Pvt. Ltd., Harni (Baroda)

(RMC batching plant)

Thank youto all of you……