LIME

One of the oldest manufactured building materials used as a mortar and plaster by all the early civilizations:

• Egyptians used lime plaster before 2600 B.C. • Greeks used it extensively for mortars and plasters• Romans developed a mixture of lime putty and volcanic

ash for the first real cement.

Manufactured by the calcination of limestone (carbonates of calcium and magnesium).

LIME: INTRODUCTION & MANUFACTURE

Calcium oxide (CaO), commonly known as quicklime or burnt lime is a widely used chemical compound.

Calcium oxide is usually made by the thermal decomposition of materials such as limestone that contains calcium carbonate in a kiln. This is accomplished by heating the material to above 825 °C.

CaCO3     →     CaO     +     CO2

Addition of water will lead to the transformation of quicklime into slaked lime also called calcium hydroxide or portlandite.

CaO     +     H2O     →     Ca(OH)2

Result is a paste, called lime putty. In contact with the atmosphere, lime putty will react following the carbonation reaction.

Ca(OH)2     +     CO2     →     CaCO3     +     H2O↑

LIME: APPLICATION

LIME: APPLICATION

LIME: APPLICATION

LIME AND CEMENT: COMPARISON

Cement hardens in days whereas lime hardness is a matter of years and that is the reason for popularity of cement.

Lime is manufactured at a temperature of 900-1200°C, whereas the temperature of the kiln in case of cement exceeds 1500°C.

Lime mortar is ecologically more preferable product, as it absorbs CO2 during hardening.

Lime has an open pore structure. Cement has a closed pore structure, which inhibits the circulation of moisture through it.

Before quicklime can be used, it must first be mixed with water in the process called slaking or hydration.

The lime has now become calcium hydroxide (Ca(OH)2), known as slaked lime or hydrated lime.

The carbonates decompose into carbon dioxide, which is expelled, and calcium oxide (CaO) called quicklime.

Quicklime

LIME

Hydrated lime mixed with water to make lime putty, is used as an ingredient of hard-finish coat for two-and three-coat Portland cement plasters. It is also used for mixing with cement mortar or concrete to:

• increase its workability• decrease its permeability

to water • reduce cracking due to

shrinkage

A type of lime which will set under water is hydraulic lime, used only where slow underwater setting is required.

LIME

Gypsum, like lime, was used as a plaster by the Egyptians, Greeks and Romans.

“Plaster” from the Greek word for both the raw material and calcined product. In architectural terminology the words “Plaster” and “gypsum” are often used interchangeably.

GYPSUM

Gypsum rock is ground fine and heated (calcined) to between 325 F. to 340 F. when it loses about three-fourths of its combined water.

The remaining product is Plaster of Paris if pure gypsum is used, or hard wall plaster if 39.5 % impurities are present or added to retard the set and improve the setting qualities. Hard wall plaster is harder than lime plaster, sets more quickly and thoroughly.

Gypsum plaster is rendered more plastic by the addition of hydrated lime.

Fiber or hair is also sometimes added for greater cohesiveness. The fiber may be hemp, sisal or jute; the hair is generally cleaned goat or cattle hair.

GYPSUM

First developed by the Romans by mixing slaked lime with pozzolana (volcanic ash) which hardened under water.

With the fall of the Roman Empire the art of cement-making was lost and for several centuries.

CEMENT

In 1756, Smeaton, an Englishman, rediscovered hydraulic cement but it was not until 1824 that Aspdin, an English bricklayer and mason, invented and patented Portland cement.

Today, the word “cement” generally refers to Portland cement which is the principal type of cement in use.

Portland cement is obtained by finely pulverizing clinker produced by calcining a proportioned mixture of argillaceous (silica, alumina) and calcareous (lime) materials with iron oxide and small amounts of other ingredients.

Types of Portland cement:• slow-setting cement• quick-setting high early

strength cement• sulfate-resisting cement for

applications where alkaline water and soils occur

• white cement (or stainless cement which is free of iron impurities).

CEMENT

Portland cement is sold in bags of 40 kilos total weight.

• Cement is the binding agent of concrete.• Something that serves to bind or unite.• A building material made by grinding limestone and

clay to a fine powder, which can be mixed with water and poured to set as a solid mass or used as an ingredient in making mortar or concrete.

DEFINITION OF CEMENT

MANUFACTURE OF CEMENT

Manufacture of Portland cement

Raw material: Calcareous, Siliceous and Argillaceous

Grinding and mixing in kiln at about 1500C

Fusion into balls known as Clinker

Cooling and grinding of Clinker with addition of Gypsum

Result is Commercial Portland cement

MANUFACTURE OF CEMENT

Quarry face

1. BLASTING 2. TRANSPORT

quarry

3. CRUSHING & TRANSPORTATION

crushing

conveyor

dumper

storage at the plant

loader

THE CEMENT MANUFACTURING PROCESS

1. RAW GRINDING

Raw grinding and burning

2. BURNING

conveyor Raw mix

kiln

cooling

preheating

clinker

storage at the plant

Raw mill

THE CEMENT MANUFACTURING PROCESS

1. GRINDING

Grinding, storage, packing, dispatch

2. STORAGE, PACKING, DISPATCH

clinker storage

Gypsum and the secondary additives are added to the clinker.

silos

dispatch

bags

Finish grinding

MANUFACTURE OF CEMENT

Chemical Name

Chemical Formula

Shorthand Notation

Percent by

Weight

Tricalcium Silicate

3CaO×SiO2

C3S 50

Dicalcium Silicate

2CaO×SiO2

C2S 25

Tricalcium Aluminate

3CaO×Al2O3

C3A 12

Tetracalcium Aluminoferrite

4CaO×Al2O3×Fe2O3

C4AF 8

Gypsum CaSO4×H2O

CSH2 3.5

http://python.rice.edu/~arb/Courses/360_04_cement.pdf

MAIN CONSTITUENTS IN A TYPICAL PORTLAND CEMENT

Tricalcium Silicate(50%)

Dicalcium Silicate(25%)

Tricalcium Aluminate(12%)

Tetracalcium Aluminoferrite(8%)

Gypsum(3.5%) Other

(1.5%)

MAIN CONSTITUENTS IN A TYPICAL PORTLAND CEMENT

• The four basic components namely C3A, C3S, C2S and C4AF are responsible for the different properties of the cement. If the amounts of these compounds are changed, the properties are also changed.

TYPES, PROPERTIES AND USES OF CEMENT

TYPES AND USES OF CEMENT

Types Salient features Use

I (OPC) Rate of strength development and heat evolution are medium

General purpose cement

II (Sulphate resisting cement)

C3A and C3S contents are comparatively lower than OPC

Aids in providing moderate resistance to sulphate attack and moderately low heat generation

III (Rapid hardening Cement)

Higher C3S content and higher fineness

When formwork is to be removed early

IV (Low heat Portland cement)

C3S and C3A contents are further lowered

For large masses

V (Sulphate resisting cement)

C3A content is reduced For extensive exposure to sulphates

Portland Cement

A hydraulic cement is a material capable of setting, hardening and remaining stable under water.

Portland cement is a hydraulic cement composed mainly of calcium silicates, obtained by heating a mixture of limestone and clay in a kiln at 1400-1600 °C.

Limestone (CaCO3) is the most common source of calcium oxide (lime, CaO).

Iron-bearing aluminosilicates are used as the primary source of silica (SiO2). Clays are preferred due to the finely divided state. The aluminum and iron oxides act as fluxing agents (i.e., decrease the fusion temperature).

Cement CompositionChemical formula Notation Name Typical

weight %

CaOSiO2

H2O

Al2O3

Fe2O3

MgOK2O, Na2O

SO3

CO2

CSHAFMK, NSC

Lime, calcium oxideSilica, silicon dioxideWaterAlumina, aluminum oxideIron or ferric oxideMagnesia, magnesium oxideAlkalis, Potassium & sodium oxidesSulphur trioxideCarbon dioxide

60-6717-25

--3-81-61-4

0.5-1.22-3.5

--

3CaO·SiO2

2CaO·SiO2

3CaO·Al2O3

4CaO·Al2O3·Fe2O3

CaSO4·2H2O

C3S

C2S

C3A

C4AF

CSH2

Tricalcium silicate, AliteDicalcium silicate, BeliteTricalcium AluminateTetracalcium AluminoferriteGypsum, Calcium sulphate dihydrate

45-6015-306-126-83-4

M. Santhanam

Hydration of Cement: Formation of Calcium Silicate Hydrate

2C3S + 7H → C3S2H8 + 3CH (ΔH = -500 J/g)Moderate reaction rate, gives high strength and heat liberation

2C2S + 5H → C3S2H8 + CH (ΔH = -250 J/g)Slow reaction rate, gives low initial but high later strength, and low heat liberation

Calcium silicates (C3S + C2S) + water → C-S-H + Ca(OH)2

Young et al.

Hydration of Cement: Formation of calcium sulphoaluminates

Ettringite (AFt) formation:C3A + 3CSH2 + 26H → C6AS3H32 (ΔH = -1672 J/g)Fast reaction rate, gives low strength and very high heat liberation

Ettringite, in the absence of gypsum, reacts further to become monosulfoaluminate (AFm) : C6AS3H32 + 2C3A + 4H → 3C4ASH12

Overall reaction:C3A + CSH2 + 10H → C4ASH12 (ΔH = -1144 J/g)

Taylor

Hydration of Cement: Formation of calcium aluminohydrate

C4AF + 2CH + 14H → C4(A,F)H13 + (A,F)H3

(tetracalcium (ferric-aluminum hydroxide) aluminate hydrate)

C4AF may also react with gypsum, as C3A does, but it is much less reactive.

Young et al.

Young et al.

Evolution of Hydration

Rate of Heat Evolution During Hydration

Mindess & Young

Stage I: Rapid evolution of heat, lasts about 15 minutes.Stage II: Dormant period, lasts until initial set occurs in 2 to 4 hoursStage III: Rapid reaction of C3S during the acceleration period, with the peak being

reached at about 8-10 hours, much after final set at 4-8 hours and hardening has begun

Stage IV: Rate of reaction slows down until steady state is reached in 12-24 hoursStage V: Steady state

Morphology of Hydration Products

Young et al.

Scanning electron micrograph of 7-day old hardened cement paste (×3500). Bottom left: cement particle coated with C-S-H surrounded by ettringite needles; Upper left: platelets of monosulfoaluminate; Right: large crystal of calcium hydroxide

Taylor; Mehta and Monteiro

Microstructure of Hydrated Cement PasteCalcium Silicate Hydrate or C-S-H gel

• C/S ratio of 1.5 to 2• High surface area (100-700 m2/g)• High covalent/ionic and Van der Waals forces• Volume – 50-65%

Mehta and Monteiro

Microstructure of Hydrated Cement PasteCalcium Hydroxide or portlandite

• Large hexagonal crystals can be formed• Low surface area (0.5 m2/g)• Low Van der Waals forces• Volume – 20-25%

Mehta and Monteiro; Mindess and Young

Microstructure of Hydrated Cement PasteCalcium Sulfoaluminates

• Ettringite (first): Prismatic needles• Monosulfate (later): Plane hexagonal crystals (low surface area: 2 m2/g) • Volume – 15-20%

Ettringite Monosulfoaluminate

Mehta and Monteiro

Microstructure of Hydrated Cement Paste

Standardization of Cement Indian Standard (BIS) Cements

Ordinary Portland Cement – IS:269-1989 (classified as 33, 43 and 53 grade; the grade implies the strength achieved by the cement mortar at 28 days)

Portland Cement, Low Heat – IS:12600-1989

Rapid Hardening Portland Cement – IS:8041-1978

Portland-Pozzolana Cement – IS:1489-1976

Portland-Slag Cement – IS 455-1976

M. Santhanam

Oxides Percentage

Lime, CaO 60-65

Silica, SiO2 20-25

Alumina, Al2O3 04-08

Iron oxide, Fe2O3 02-04

Magnesia, MgO 0.1-3

Sulphur trioxide, SO3 1-3

Alkalis (K2O, Na2O) 0.5-1.3

CHEMICAL COMPOSITION OF OPC

Type of Cement Compound Composition (%)

C3S C2S C3A C4AF CaSO4 Free CaO

MgO

Type-I Ordinary Portland

50 24 11 8 2.9 0.8 2.4

Type-II Modified Cement

42 33 5 13 2.8 0.6 3.0

Type-III Rapid Hardening Portland

60 12 10 8 3.9 1.3 2.6

Type-IV Low Heat Portland

31 45 5 12 2.9 0.3 2.7

Type-V Sulphate Resistant Portland

40 40 4 9 2.7 0.4 1.6

AVERAGE VALUES OF COMPOUND COMPOSITION OF PORTLAND CEMENTS OF DIFFERENT TYPES

HYDRATION

When Portland cement is mixed with water its chemical compound constituents undergo a series of chemical reactions that cause it to harden (or set).

This chemical reaction with water is called "hydration". Each one of these reactions occurs at a different time and rate. Together, the results of these reactions determine how Portland cement hardens and gains strength.

Dry cement

Water

HYDRATION

• Tricalcium silicate (C3S). Hydrates and hardens rapidly and is largely responsible for initial set and early strength. Portland cements with higher percentages of C3S will exhibit higher early strength.

• Dicalcium silicate (C2S). Hydrates and hardens slowly and is largely responsible for strength increases beyond one week.

• Tricalcium aluminate (C3A). Hydrates and hardens the quickest. Liberates a large amount of heat almost immediately and contributes somewhat to early strength. Gypsum is added to portland cement to retard C3A hydration. Without gypsum, C3A hydration would cause portland cement to set almost immediately after adding water.

• Tetracalcium aluminoferrite (C4AF). Hydrates rapidly but contributes very little to strength. Its use allows lower kiln temperatures in portland cement manufacturing. Most portland cement color effects are due to C4AF.

HYDRATION

FinenessFineness, or particle size of portland cement affects

hydration rate and thus the rate of strength gain. The smaller the particle size, the greater the surface

area-to-volume ratio, and thus, the more area available for water-cement interaction per unit volume.

PROPERTIES

SoundnessDuring setting and hardening, the cement undergoes

changes in volume. If this change is considerable, the cement is unsound.

An unsound cement results in cracking and disintegrating of concrete.

PROPERTIES

Setting Setting refers to a change from a fluid to a rigid state. Normally, two setting times are defined

Initial set. Occurs when the paste begins to stiffen considerably.

Final set. Occurs when the cement has hardened to the point at which it can sustain some load.

PROPERTIES

Strength Strength reflects the ability of a material to

withstand external force. Cement is weak in tension and much stronger in compression. Normally, three types of strength are studied. Direct tension test: Performed on a 1:3 mortar briquette

25.4 x 25.4 x7 6.4 mm (IS). Compression test (ASTM C 109-92): Performed on a 1:2.75

mortar cube (51 mm or 2 in. side) with W/C ratio of 0.485.

PROPERTIES

Visual TestsColorPresence of lumps

Adulteration testStrength test

FIELD TESTING OF CEMENT

High Alumina Cement It develops 80% ultimate strength at 24 hours. High alumina cement is made from calcarious rock and bauxite (abundant in

Aluminium) High alumina cement is used in cold weather and under seawater applications.

White Cement For architectural purposes The grey color of cement is due to the presence of iron. White cement has a very

minimal iron content and is exposed to gas or oil fuel heating instead of coal. Colored Cement

For architectural purposes Expansive Cement

Against shrinkage cracks Low Alkali Cement

Against deleterious aggregates

SPECIAL CEMENTS

Cement should be protected at the building site from injury through contact with dampness.

They should be stored in shed with a wood floor raised about 300mm (12”) from the ground.

STORAGE OF CEMENT

Cement is soft and silky to the touch. If it has lumps that do not readily break, the cement has already absorbed a damaging amount of moisture.

Cement should be used as soon as possible after delivery.

Piles should be limited to twelve sacks in height.

Warehouse set - when the cement is stored in high piles for long periods, there is a tendency for the lower layers to harden caused by the pressure above.

• Fly ash is the finely divided residue resulting from the combustion of ground or powdered coal

• Fly ash is a waste by-product material that must be disposed of or recycled.

• 131 million tons of fly ash are produced annual by 460 coal-fired power plants in the U.S. alone.

Fly Ash : Introduction

• Because fly ash is a by-product material chemical constituents can vary considerably but all fly ash includes:– Silicon Dioxide (SiO2)– Calcium Oxide (CaO) also known as Lime– Iron (III) Oxide (FeO2)– Aluminum Oxide (Al2O3)

• Depending on source coal may include on or more toxic chemicals in trace amounts:– Arsenic, Beryllium, Boron, Cadmium, Chromium, Cobalt, Lead,

Manganese, Mercury, Molybdenum, Selenium, Strontium, Thallium, and Vanadium.

Chemical Composition

Flyash Vs. Clay : Composition

• ASTM C618 Defines two classes of fly ash:– Class C– Class F

• ASTM C618 requirements:– Loss of Ignition (LOI) < 4% – 75% of ash must have fineness of 45 µm or less

• Primary difference between Class C and Class F fly ash is the amount of the amount of calcium, silica, alumina, and iron content in the ash

Classes

• Class F fly ash– Produced from burning harder, older anthracite and bituminous coal.– Contains less than 20% lime– Requires cementing agent like PC, quick lime, hydrated lime– Used in

• high sulfate exposure conditions• Used for structural concretes, HP concretes, high sulfate exposure concretes • Useful in high fly ash content concrete mixes

Class F and Class C Fly Ash

Class C fly ash Produced from burning younger lignite and sub-bituminous coal Higher concentration of alkali and sulfate Contains more than 20% lime Self-cementing properties Primarily residential construction Limited to low fly ash content concrete mixes

Flyash: Some Properties

Class C

Classes

Class F

• In the past fly ash produced from coal power plants was simply entrained in flue gasses and released into the environment. Now in the U.S., EPA regulations requires greater than 99% of total fly ash produced in a plant to be captured and either stored, recycled, or disposed.

• Worldwide, more than 65% of fly ash produced in the world is disposed of in landfills or ash ponds.

• In India alone fly ash landfills comprise 40,000 acres of land.

Disposal

• General environmental advantages:– Diverts material from waste stream– Reduces the energy investment in processing virgin materials– Conserves virgin materials– Reduces pollution

• An Estimated 43% of fly ash generated in the U.S. is re-used. • 131 million tons of fly ash are produced annually and

approximately 56 million tons of that fly ash is recycled. • Recycling this fly ash saves approximately 36,700 acre-ft of

landfill space which is equivalent to roughly 28,200 football fields one foot deep.

Recycling

• Brick and CMU• Portland Cement and Grout• Embankment/ Structural Fill and Mine Reclamation• Road Sub base• Soil Stabilization• Flowable Fills (CLSM)• Waste Stabilization and Solidification• Raw Feed for Cement Clinkers• Numerous Agricultural Applications

Fly Ash : Applications

Fly Ash Bricks

• Fly ash bricks are durable, have low water absorption, and are economical/eco-friendly.

• Fly ash bricks can have up to three times the strength of conventional bricks

• Flyash bricks can be divided into the following four types

Clay Fly ash Bricks.Fly ash – Sand Lime Bricks.Cold Bonded Lightweight Fly ash BricksFlux Bonded Fly ash Bricks

Fly Ash Bricks : Types

Normal Bricks Vs. Clay Fly Ash Bricks : Properties

• Manufacturing process of clay fly ash bricks by manual or extrusion process involves mixing of fly ash (60 %) with clay of moderate plasticity.

• The green bricks are dried under ambient atmospheric conditions.

• Dried bricks are fired in traditional brick kilns at 1000º ± 1000º C with a soaking period of 5 – 7 hours at maturing temperature.

Clay Flyash Bricks : Production

• Clay (wt%) :50• Fly ash (wt%) :50• Forming pressure (Kg/ cm2) : 300• Curing time (h) : 6• Curing Temp. : 950 0C

• Under these circumstances Firing shrinkage(%) : .56 Water adsorption(%) : 20.2 Weight per unit volume(Kg/cm3) : 1379 Firing loss(%) : 6.05

Clay Fly Ash Bricks Making: Standard Parameters and properties

Clay Fly Ash Bricks Making : Selected Parameters

• No of sample of each composition: to be selected

• Each Sample will be fired in the furnace at 750,850 and 950 0C

• The compositions given here are on dry basis. In every specimen, 14 wt% water will be added (correct water percentage to allow good, dense compaction of the clay, and the brick will release easily from the mould)

• Compressive strength testGreen Compressive strength (GCS) testDry Compressive strength (DCS) test

• Water adsorption test• Shrinkage test• Firing loss test• Weight per unit volume loss test etc.

Clay Fly Ash Bricks Making : Tests To Be Done

• Appearance : Uniform in shape Smooth in finish, Bricks are of dense composition, Free from visible cracks, Colors can be altered with the addition of

admixtures

• Compressive strength of fly ash bricks is 9.00 N/mm2 (as against3.50 N/mm2 for handmade clay bricks)

Clay Flyash Bricks : Performance

• Thermal properties Thermal conductivity is 0.90-1.05 W/m2 ºC (20-30% less than those of

concrete blocks). Do not absorb heat; reflects heat and gives maximum light reflection without

glare.

• Durability and moisture resistance These blocks are highly durable Water absorption is 6-12% as against 20-25% for handmade clay bricks,

reducing dampness of the walls.

• Buildability, availability and cost Easy workability and high compressive strength eliminates breakages/wastage

during handling giving a neat finish, with lower thickness of joints and plaster

Clay Flyash Bricks : Performance( Cont.)

The bricks being available in several load bearing grades are suitable for use in

Load bearing external walls, in low and medium size structures.

Non-load bearing internal walls, in low and medium size structures.

Non-load bearing internal or external walls, in high-rise buildings

Clay Fly Ash Bricks: Applicability

AGGREGATES

• Aggregates are granular Mineral Particles• Aggregates combined with cement to form

concrete or asphalt surfaces. • Alone as road bases or backfilling • Properties required in an aggregate depends

on its proposed used. But the type of aggregates, their basic properties, and tests used to evaluate these properties apply to most uses.

USES• Portland cement concrete, Asphalt concrete,

and Asphalt surfaces • Road bases and sub bases • Railroad ballast • Trench backfill • Fill under floor slab • Concrete blocks. • Water filtration beds. • Drainage structures

Aggregates Sources• Natural sand & gravel deposits • Crushed rock • Slag & mine refuse • Rubble & refuse • Artificial aggregates • Pulverized concrete and asphalt pavement

Role of Aggregates in Concrete

60-80% of the volume of concrete is occupied by aggregates.

Main significance:• Cost• Dimensional stability• Strength and stiffness• Abrasion resistance

Size Gradation of Aggregates

Mindess & Young

uniform size continuous grading smaller versus larger sizes

gap grading no-fines

- a proportioned mixture of siliceous materials (sand, crushed stone) and cement (lime, Portland) which, after being prepared in a plastic state with water, hardens into a stonelike mass.

MORTARS AND PLASTERS

• Mortar is cement mix used to glue masonry units to each other, or other surface finishing materials like tiles, bricks, stones to a receiving structure like a wall or floor.

• Plaster is mortar applied to wall surfaces as a preparation or a hard finish coat.

CEMENT MORTAR

- is a proportioned mixture of cement, fine aggregate and water.

- For first-class mortars 1 part of cement should be added to not more than 3 parts of sand.

- Replacing 10 or 15 percent of the cement by volume with hydrated lime gives greater workability and increases the strength of the mortar.

- For rubble stonework, 1 : 4 will be much stronger than lime mortar.

- For the top surface of floors and walks, use 1 : 1 to 1-1/2.

- Mortar made with fine sand requires a much larger quantity of cement to obtain a given strength than mortar made with coarse sand.

CEMENT MORTAR

- Mortar may be mixed by hand or mechanical mixers, the latter being preferred for large quantities.

- When the mixing is done by hand, it should be done on platforms made watertight to prevent the loss of cement.

- The cement and sand should be mixed dry in small batches in the proportions required on a clean platform.

- Water is added and the whole remixed until it is homogeneous in color and leaves the mixing hoe clean when drawn out.

- Mortar should never be retempered after it has begun to set

PLASTER

- is a mortar of cementitious material ( lime, gypsum or cement), sand and water which is applied in coats (layers) to masonry surfaces, lath or various types of plaster board to give a hard finish surface to interior or exterior walls and ceilings.

- the word “plaster” refers to gypsum plaster and the words gypsum and plaster are often used interchangeably.

- Fiber or hair is sometimes added to the mixture to give increased strength as when used for the first coat.

- Plastering is done according to two basic methods: two-coat and three-coat. A three-coat job consists of :

• a first binding coat called scratch coat;• a second straightening coat called the brown-coat; and • a final coat called the finish coat.

In the two-coat work, the scratch and brown coats are combined into one.

TYPES OF PLASTER AND THEIR USES

a. Lime Plaster

Lime putty (hydrated lime and water), mixed on the job with sand and gypsum plaster, used for two and three-coat finish surfaces for interior walls and ceilings.

Scratch coat : 1 part lime putty, 1 part Portland cement or Keene’s cement, 2-3/4 parts sand by weight.

Brown coat : 1 part lime putty, 1part Portland cement or Keene’s cement, 3 parts sand by weight.

Finish coat: Hard finish : 1 part lime putty, 1/3 gypsum plaster by

volume Sand float : 1 part lime putty, ¼ gypsum plaster, 2 parts sand

by volume

TYPES OF PLASTER AND THEIR USES

b. Gypsum Plaster

• Gypsum plaster. Plaster of Paris mixed with clay, lime and other materials in combinations covered by trademarks or patents. Mixed on the job with water, sand, lime putty, hair or fiber for two or three-coat finish surfaces for interior walls and ceilings; or used dry as ingredient for hard or sand float finish with lime plaster (see above).

• High-strength gypsum plaster. Same as gypsum plaster but mixed to meet established standards. Mixed on the job with water, sand, lime putty, hair or fiber for two and three-coat finish surfaces for both exteriors and interiors.

- Scratch and brown coats : 1 part high-strength gypsum plaster to 2 parts sand by weight.

- Hard finish : ¼ lime putty to 1 part high-strength gypsum plaster by volume

TYPES OF PLASTER AND THEIR USES

b. Gypsum Plaster

• Fibered gypsum plaster. Gypsum plaster premixed with fibers. Mixed on the job with water and sand for scratch coat for three-coat plastering job

• Prepared gypsum plaster. Gypsum plaster mixed with fine white sand. Used for two and three-coat finish surfaces for interior walls and ceilings .- Scratch and brown coats : mix per manufacturer’s

instructions.- Finish coat: Any type of final coat plaster

(gypsum, Keene’s cement, lime or prepared finish coat

TYPES OF PLASTER AND THEIR USES

b. Gypsum Plaster

• Bonding plaster. Gypsum plaster mixed with ingredients develop more adhesive strength in combinations covered by trademarks or patents. Used for interior finish for smooth concrete walls or ceilings. Mix and apply as per manufacturer’s directions

• Lightweight gypsum plaster, fire-resistant plaster. Gypsum plaster mixed on the job with water, perlite, vermiculite or other suitable mineral aggregate. Lightweight gypsum plaster is used when weight is important, and for fire-proofing other materials such as steel. Applied on lath. For interior use only .- Scratch and brown coats : 2 sand, 2 cu. ft. perlite or vermiculite per 100

lb. of plaster.- Brown coat: 3 sand, 3 cu ft. perlite or vermiculite per 100

lb. of plaster.- Finish coat: Hard finish: 1/3 gypsum plaster, 1 lime putty by volume Sand Float Finish: 1 gypsum plaster, 1-1/2 sand by volume

TYPES OF PLASTER AND THEIR USES

b. Gypsum Plaster

• Keene’s cement. Plaster of Paris mixed with alum or borax or other materials and burned (calcined) at 932F. Mixed on the job with water, lime putty and fine white sand as hard finish for two and three-coat gypsum plaster. For interior use only

- Hard finish : 1 Keene’s cement, ¼ lime putty, 1/10 fine white sand by weight .

- Sand float finish : ½ Keene’s cement, 2 lime putty, 4 ½ sand by volume.

• Plaster of Paris. For ornamental plaster work and castings.

• Molding plaster. For ornamental plaster work and castings. Mix with water as per manufacturer’s directions.

• Acoustics plaster. For acoustic treatment of interior walls and ceilings. Applied on gypsum plaster base coats. Mix with water as per manufacturer’s directions.

TYPES OF PLASTER AND THEIR USES

c. Portland Cement Plaster

• Mixed with water, sand and lime putty. Used for two and three-coat finish surfaces for exterior and interior walls and ceilings - Scratch and brown coats : 1 cement, ¼ lime putty, 3 sand.- Sand float finish : 1 cement, ¼ lime putty, 3 sand.

• Thickness of plaster coats depends on the type of material to which the plaster is applied. Generally, the total thickness is 5/8” on metal lath and ½” on lathing board and gypsum block.

• In three-coat plastering work, the scratch and brown coats are ¼” thick at minimum; the finish coat is 1/8” with a minimum of 1/16” at any point.

• For two-coat work, the base coat is ½” and the finish coat is the same as three-coat work.

TYPES OF PLASTER AND THEIR USES

d. “Sgraffito”

• is highly decorative type of plaster work developed in Italy during the Renaissance. This type of technique consists of applying two or three thin coats of plaster different colors and then cutting away certain areas of one or two coats to produce a three-dimensional colored design.