Session 7 Plaster

8/10/2019 Session 7 Plaster

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Plastering

1. Objectives And Requirements of Plastering.

2. Material for plastering.

3. Tools for plastering.

4. Method of Plastering.

5. Special External Finishes.

6. Precautions required to take before plastering7. Defects in plastering.


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Objectives of Plastering

1. Provide a even, smooth,durable surfacefor finishing.

2. Protect the construction material such asbrick, and concrete.

3. Conceal the defective workmanship.

4. Conceal the use of defective material.5. Specially for internal plaster- make dust

proof surface.


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IMPORTANT TECHNICAL TERMS

Background :-The surface to which first coat ofplastering is applied is called background.

Dubbing out: - The filling the hollow spaces of the background before applying the plaster is called dubbing out.

Finishing coat:- The final layer of the surface finish iscalled finishing coat.

Hacking:- The process of making the background rough toact as key for plastering is called hacking.


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Requirementsof plaster mix

1. It should provide nonabsorbent surface.

2. It should not contract in volume while

drying and setting.

3. It should adhere to the surface.

4. It should offer good resistance against

sound and fire.

5. It should give good decorative effect.


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Mortars used in plastering

Mud mortar

Lime mortar

Cement mortar

Water proof mortar


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Tools for Plastering


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Method of plastering

Plastering: Estimation of quantity of materials (for 10 m2)

Thickness

of plaster

in mm

Mortar

Quantity

in m3

Cement Sand (1:3) Cement Sand (1:4) Cement Sand (1:6)

Cement

m3

Sand

m3

Cement

m3

Sand

m3

Cement

m3

Sand

m3

6 0.072 0.0256 0.077 0.019 0.077 0.012 0.077

10 0.12 0.0426 0.128 0.032 0.128 0.021 0.128

12 0.144 0.0513 0.154 0.038 0.154 0.025 0.154

15 0.172 0.0613 0.184 0.046 0.184 0.030 0.184

18 0.216 0.0770 0.231 0.057 0.231 0.038 0.231

20 0.224 0.0800 0.240 0.06 0.240 0.06 0.240


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Special external finishes for plastered surface

1. Rough cast finish

2. Smooth cast finish

3. Pebble dash finish

4. Depeter Finish

5. Sand face Finish6. Scrapped Finish

7. Textured Finish/Stucco Finish


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Rough cast plaster: Estimation of quantity of materials (for 10 m2)

Rough cast plaster with a mixture of sand and gravel or crushed stone from 4.75 mm to 10 mm nominal

sized dashed over and including the fresh plaster in two layers, under layer 12 mm cement plaster 1:4 andtop layer 10 mm cement plaster 1:3 mixed with 10 % finely grounded hydrated lime by volume of cement

Item in 10 m2 Mortar

Quantit

y in m3

Coarse Sand

Quantity in

m3

Find Sand

Quantity in

m3

Cement

In Kg

Aggregates of

size in between

4.75 to 10 mm in

m3

(a) 12 mm under layer 1:4 0.144 0.16 - 55

0.10(b) 10 mm top layer 1:3 0.12 - 0.13 61

(a) 12 mm under layer 1:5 0.144 0.16 - 44

0.10(b) 10 mm top layer 1:3 0.12 - 0.13 61


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Various materials used in plastering

Sr. No. Type of Material Properties of Material

1

Plaster of Paris: Heating the Gypsum 1) Adheres well to any surface like

wood, brick, Cement plaster, metalsetc.

2) Provide smooth surface.

3) White in colour and hence used for

ceiling plasters.

2 Acoustic Plaster: Gypsum + water Form tiny bubbles in the plaster coat

which absorb the sound waves

3 Barium Plaster: Barium Sulphate Absorbs X-rays hence used in X-ray

rooms

4 Asbestos- Marble mortar Provides marble like Finish

5

Keenes Cement: mixture of Plaster ofParis and alum

1) White in colour, and having glasslike finish

2) Quite costly and used only for

Internal works

6 White Cement or Coloured cement 1) Provide good finish to the surface.

2) It gives hard and durable surface


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Precautions required to take before plastering

1. Suction effect of background

2. Initial set of plaster mix

3. Shrinkage cracks

4. Mixed background

5. Thickness of plaster6. Mortar mix

7. Number of coats

8. Sand for plaster

9. Sequence of plastering

10. Preparation of surface

11. Preparation of mix

12. Curing


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Defects in Plastering

Cracking

Blowing/ Blistering of Plaster

Falling out of Plaster

Efflorescence on Plaster Surface

Popping and Crazing


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Defects in Plastering

Blistering or Blowing of the plasterThis Consists of formation of one or more

swellings in small patches over the finished

plastered surfaces. This is caused due tofaulty slaking of the lime. Properly slaked

lime should be used.


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Defects in Plastering Falling out of the Plaster

in this, plaster from the same portion of the surfacecomes out & results in the formation of patches. It is

called a peeling.

Causes:

1. Due to lack of adhesion

2. Excessive Moisture

3. Excessive moisture changes

4. Rapid drying of the plaster

5. Insufficient drying between each coat of plaster


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Defects in Plastering Cracking

This consists of formation of cracks, in the

plaster work.

Reasons:

1. Structural defects in the building

2. Old surface not properly prepared

3. Wet background4. Excessive shrinkage of the thin coats

5.


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Recent advances/ Latest trends SINICON PP ( Patented Technology )

It is a material derived from special kind ofvolcanic glass.

This volcanic glass is processed and

converted into well sealed tough glassgranules which is cementitious and is a good

replacement for sand in plastering.

Each granule consists of glass walled closedcells each enclosing near vacuum.

SINICON PP

SAND + CEMENT+WATER = PLASTER


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SINICON PP ( Patented Technology )

How does it work

Sinicon PP makes home behave like a thermos flaskScientifically it is a material with millions of vacuum cells

in each granule with less thermal conductivity./

Formation of the vacuum cells is a characteristic property

of the material.

A building plastered using SINICON PP, substantially

resists the ingress of heat/cold in the structure.

If 20 mm thick Sinicon PP plastered brick wall wouldeffectively provide a reduction of heat equal to twin brick

wall !


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Physical Properties

Not flamable. It is safe to handle like sand.

Not explosive. It is safe to handle like sand.

Not hazardous to skin. Could be cleaned with water.

Not hazardous to eyes except abrasion. Washable withwater.

Not hazardous to Ingestion however avoid ingestion. If

consumed, drink 2 x 250 ml of water to dilute.

Not Toxic.


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Material Properties

1. Exceptional Fire Resistance2. Excellent Thermal Insulator

3. Light Weight

4. Low Water Permeability5. Good Adhesion (in Plaster)

6. Zero Smoke and Zero Fumes

7. Non-Toxic Dust


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Advantages

A Substitute for sand in plastering and otherapplications.

1. K value ( thermal conductivity constant less)

2. Water permeability low

3. Increases durability/ life of the structure

4. Can be used over a roof

5. Can be used internal/external ( both

recommended )

6. Possible to use as a Fire proof seal

7. Both old and new buildings


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How SINICON PP is used

It is a direct replacement for sand while

plastering.

Mixing in a ratio of 4.5:1 ( S: C) .

To prepare this a ratio of 1.5 bag of SiniconPP and 1 bag of cement + 36 litres water

Area coverage

Roof : 20 mm thk = 50 Sq. Ft25 mm thk = 40 Sq.Ft

Wall : 12 mm thk = 75-80 Sq. ft


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Pointing

1. Introduction

2. Method of pointing

3. Types of finishes to joints


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Pointing

It is finishing the mortar joints in the exposed

brick or stone masonry with suitable cement or

mortar joint.

Scope of pointing

1. Where smooth or even finish not required

2. Beauty of materials to be retained


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POINTING

Final treatment with cement or lime mortar made to the joints ofthe masonry to provide neat appearance is termed aspointing.

The joint on the face of stone or brick masonry are roughly filledin while the walls are being raised.

They are after wards neatly finished off to make them water tight.

The joints thus finished, give a better appearance to surface and

prevent rain water from entering the interior of the masonry.


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PURPOSE

1. To prevent the moisture and the rain water

from entering the interior of masonry

through joints and to make them durable.

2. To improve the appearance of the

structure.


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SUITABILITY

Pointing is preferred to plastering under following

conditions.

1. When a smooth and even surface is not

essentially required.

2. Where it is desirable to exhibit to view the

natural beauty of the materials (bricks or stones)

used in construction.

3. When the workmen ship is neat and good.


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TYPES OF POINTING

The selection of particular type of pointing

depends upon the types of bricks or stoneused and the appearance required..


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TYPES OF POINTING (-ctd-)

1. Flat or flush pointing

In this pointing, the mortar is pressed tightly and the

joints are filled up and made flush with the face of the

wall.

This is the simplest type of pointing and is provided

extensively.

It is economical and durable because it requires lesslabor than all other pointing.

It does not afford a lodging place for dust.


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2. Struck pointing

In this pointing the face of the mortar joint instead ofkeeping it vertical, its upper side is kept about 12 mminside the face of the masonry and the bottom is kept

flush with the face of the wall as shown in fig 14.2.

This pointing has a better effect of throwing rain water.

This is also known as ruled pointing.

This pointing is the best in ordinary circumstances.


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3. Recessed pointing

In this pointing the face of the mortar joint ispressed inside by means of a suitable tool and is

left vertical instead of being made inclined.

This pointing is provided when face work of good

textured bricks with good quality mortar is used.


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4. V-pointing

This type of pointing is provided by forming a v-shaped groove inside the mortar of the joint with a

special tool (steel or iron jointer).

This pointing is commonly recommended for

brick work in case of governmental buildings.


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5. Weather pointing

This is similar to V-Pointing but in this caseinstead of pressing a v shaped grooveinside, it is provided by forming a v shapedprojection outside the walls surface.

This pointing is generally recommended forsuperior brick work.


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6. Keyed or grooved pointing

In this case, the joints are first filled up flush, and then acircular piece of steel or iron is pressed in and rubbed in

the middle of joints.

Grooved pointing has a big groove in the face thankeyed.

Keyed pointing gives an attractive appearance to thestructure and is generally used for superior work.


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Types of Finishes for Pointing joints


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Types of Finishes for Pointing joints


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Pointing: Estimation of quantity of materials (for 10 m2)

Item in 10 m2 Mortar

Quantityin m3

Sand

Quantityin m3

Quantity of cement

Cement

in m3

Cement in

bags

Brick masonry wall with Flush,

Struck, Keyed pointing

0.03 0.032 0.0107 0.31

Brick masonry wall with Vgroove, cut, beaded pointing

0.046 0.049 0.016 0.47

Brick Flooring 0.02 0.022 0.0072 0.20

Brick tile work 0.046 0.0489 0.016 0.47

Stone work with Flush, Struck,Keyed pointing

0.023 0.025 0.008 0.24

Stone masonry wall with V

groove, cut, beaded pointing

0.038 0.41 0.014 0.39


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White washing

1. Preparation of white wash.

2. Preparation of Surface.

3. Application of white wash

C l W hi


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Colour Washing

Buff Colour Wash Multani Mitti + White

Wash

Green Colour Wash Boiled Mango Bark

+White wash + Tootia (Copper Sulphate)

Blue Colour Wash Burnt Coconut Shells +

White Wash

Yellow Colour Wash Yellow earth + White

wash

Pink Colour Wash Vermiclion + White Wash

Documents

Session 7 Plaster