Engineering materials include cementing materials, lime, cement, gypsum plasters, ceramics, glass, clay products, refractories, abrasives, composites, adhesives, lubricants, rocket fuels, and insulators. Their properties and applications depend on their chemical, electrical, mechanical, optical, physical, thermal, and technological characteristics. Common engineering materials are discussed, including their composition, manufacturing processes, properties, and uses.

1. ENGINEERING MATERIALS
Engineering Materials consist of:-
1. Cementing and binding materials
2. Lime
3. Cement
4. Gypsum plasters
5. Ceramics
6. Glass
7. Clay Products

2. 8. Refractories
9. Abrasives
10. Composite
11. Adhesive
12. Lubricants
13. Rocket fuels
14. insulators

3. The field of application of a particular engineering
material are governed by the characteristics and
various properties such as:-
1. Chemical properties: Reactivity, Solubility, chemical
effects like corrosion, acidity
2. Electrical properties: Insulations, Dielectric strength
3. Mechanical properties: Elasticity, hardness.
4. Optical properties: Transmission, refractivity,
reflectivity.
5. Physical Properties: Bulk density, durability,
porosity, fire resistance.
6. Thermal properties: Thermal expansion, specific
heat
7. Technological properties: Castability, Weldability

4. Cementing and Building
materials
 These are inorganic materials.
 Having the tendency of setting and hardening
on mixing with water or air.
 Two types:
(i) Hydraulic cementing materials: Portland
cement
(ii) Non-Hydraulic cementing materials:
Lime

5. Lime

6. LIME:-
Lime is calcium oxide obtained by calcination
(heating to red hot in the presence of air) of
naturally occurring CaCO3 in the form of
limestone, chalk, marble to about 900̊ C so that all
the CO2 and moisture content removed from it.
CaCO3 calcination CaO + CO2

8. Types of Lime
Different types of lime obtained depending of the
chemical composition of lime stone. Limestone
usually contain magnesium carbonate, aluminium
oxide, iron and silicon oxide.
Four Types:
1. Fat lime or high-calcium lime
2. Dolomitic or high-magnesia lime
3. Hydraulic lime
4. Lean or poor lime

9. Fat Lime
 Contain 95% CaO and less than 2% oxides of
iron, aluminium and silicon.
 Non-hydraulic cementing material, setting occur
only by drying.
 During its slaking large amount of heat is evolved.
Uses: 1) Whitewashing and plastering the walls.
2) With sand form lime mortar to fill the joints.
3) Used in metallurgical processes
4) Used for water softening
5) Used in glass industry

10. Dolomitic Lime
 Obtained from naturally occurring dolomite
(CaCO3.MgCO3).
 It contain more than 25% of MgO.
 It slakes very slowly with less heat evolution.
 It yields plastic mortar with an easy and
smooth working.
 Uses: Used in the formation of basic
refractories and as a flux in metallurgical
process.

11. Hydraulic lime
 It is obtained from the lime stone containing
5-30% clay.
 Due to hydraulic properties set to hard mass
on immersing in water.
 It slakes with difficulty
 Uses: Used as a substitute for cementing the
thick walls and marine works.

12. Lean or poor lime
 It contain 70-80% CaO, >5% MgO and
smaller proportion of silica and alumina.
 It slakes slowly and shows a behavior in
b/w fat lime and dolomitic lime.
 Uses: It is used to make mortar for interior
works and plaster finishing.

13. Manufacture of lime
It is manufactured by calcination of limestone
in vertical kiln using coal or producer gas as
fuel.

14. Properties of Lime
 Slaking – Exothermic reaction. (280 kcal/kg)
(volume increases to 2-21/2 times)
 Plasticity – Easy spreading (MgO improves
plasticity)
 Sand carrying capacity – to reduce the shrinkage
of lime (fat lime > dolomitic lime) (CaO has
greater sand carrying capacity)
 Setting and hardening – Involve hydration and
carbonation
 Hardness – High Mg content better hardness

15. Gypsum Plaster
 Gypsum (CaSO4.2H2O)
 CaSO4.2H2O CaSO4.1/2H2O
150 ̊ C Hemi hydrate
600̊ C
800 ̊ C
CaO + SO3 CaSO4
Anhydrite

16. Applications of Gypsum
1. Plaster of Paris: It is CaSO4.1/2H2O form of
gypsum. Used in making plaster casting
moulds, indoor wall plastering. In plaster
boards.
2. Keen’s plaster: It is CaSO4 form of gypsum. It is
less soluble in water as compared to hemi-
hydrate so set and harden slowly. Used for
plastering exterior walls.
3. Estrich Plaster: It is obtained by heating
gypsum above 800 ̊ C . Set and hardened very
slowly.

17. Cement: It is a lime based product
having adhesive and cohesive
properties.

18. Manufacturing of Cement

20. Chemical Composition of Cement
The cement is usually expressed in terms of CaO,
SiO2, Al2O3, Fe2O3. These oxides exist in the
form of four phases :-
1. Dicalcium silicate, 2CaO.SiO2 (abbreviated As
C2S)
2. Tricalcium silicate, 3CaO.SiO2 (abbreviated As
C3S)
3. Tricalcium aluminate, 3CaO.Al2O3
(abbreviated As C3A)
4. Tetracalcium aluminoferrite,
4CaO.Al2O3.Fe2O3 (abbreviated As C4AF)

21. Points to remember
 The free oxides of CaO, MgO, K2O, Na2O,
TiO, SO2, H2O, CO2 constitute the remaining
10% weight of cement.
Mg rich dolomitic limestone is not suitable
for cement manufacturing since the MgO
being less basic than CaO does not readily
react with the acidic oxides of clay and
remains as such in the clinker.

22. Setting and Hardening of
cement
The process of setting occur in two stages:-
1. Initial set: It depends on temp. and
quantity of H2O. For portland cement it is
45 minutes
2. Final setting: It occur over a few hours
(about 10 hours for portland cement).

23.  Hardening a slow process takes a few days for
the complete crystallization.
 The setting and hardening process is a hydration
process in which hydrated calcium silicate
formed in the gel form called tobermolite gel.
 This gel precipitate over the cement grains and
slow down the initial fast hydration.
 The setting time and properties of the cement
depends on the alumina and ferric oxide content,
a higher content accelerate the setting process.

24. Important points
 The rapid hydration of alumina causes the
quick setting, it is controlled by addition of
gypsum ( 2 – 5 % ) to clinker to retard the
setting time.
 Large excess of gypsum leads to cracking of
the set cement due to expansion.
 Other substances such as POP, anhydrite,
sugar decrease the setting time and alkali
carbonates, chlorides, accelerates the setting
process.

25. Types of cement
1. Natural cement: mixture of natural
calcareous and argillaceous material.
2. White portland cement: free from iron
oxide.
3. Pozzolona cement: 45-65% silica, 10-20%
alumina, <10% ferric oxide, some minor
oxides of Ca, Mg, Na, K, Ti.
4. Water proof cement: mixture of portland
cement and calcium stearate or non-
saponifiable oil.

26. 5. Slag cement: Highly resistant to sea water and
sulphate solution. It is the mixture of blast
furnace slag, Ca(OH)2 and CaSO4.
6. Super sulphated cementand and High alumina
cement: resistant to sea water and sulphate
solution.
7. Portland blast furnace cement: decreased rate of
hardening.
8. Barium and strontium cement: Here Ca is
replaced by Ba and Sr. Used to form concrete act
as radiation shield.
9. Slow setting cement: Mixture of portland
cement with starch or cellulose as retarders.

27. Weathering of cement and
Concrete
Due to the environmental conditions the
deterioration of cement and concrete. There are
two types of environmental conditions:-
1. Attack by acid solution of CO2,
organic and inorganic acids:- Attack of
these acids increases with decrease in pH. Acidic water
damage the Lime structure and hydrolyse the
aluminate and silicate.
Prevention: Coating the cement with protective agents
such as drying oil, epoxy resin paint, paint with SiF4.

28. 2. Attack of sulphate solution:
Sulphate solution react with Ca(OH)2 to form
gypsum. The C3A phase of hardened cement react
with CaSO4 form Calcium sulphoaluminate with a
huge increase in volume (about 227%) . This volume
expansion lead to the destruction of cement and
concrete.
Prevention:
1) By increasing the amount of C4AF in cement which
form a protective layer of C4F.
2) By curing with superheated steam which converts
the free Ca(OH)2 into more resistant hydrated
mono calcium silicate.

29.  Supersulphated steam and high alumina
cement have greater resistance to sulphate
attack.
 Supersulphated steam is a mixture of
granulated slag(80 – 85 %), anhydrite(10-
15%) and portland cement (5%).
 Alumina cement consists of equal
proportions of alumina and lime, 20 % iron
oxide and 4-7 % silica.
 The hardened supersulphated and alumina
cement cannot react further with sulphate as
no free lime is available.

30. Admixtures of Concrete
Chemical substances added to improve the
properties of cement. Admixture include:-
1. Air entraining agent: They form microscopic
bubbles when added to concrete with water and
get attached to hydrophobic part. Concrete has
pores which retains water and during winter season
they expand on freezing and leads to cracking and
if it contains air entrainer it prevents its cracking.
e.g. oleic acid, caprylic acid.
2. Water decreasing agent: These decrease the
water content up to 10-20% without affecting the
structure of cement. e. g. melamine formaldehyde
resin and sulphonate.

31. 3. Setting accelerators: e. g. CaCl2, Calcium
formate accelerate the hydration of C2S anf C3S
phases of cement.

32. Ceramics:
Clay products are further classified as:
White ware : White/ pale cream with a
refractory body and glaze.
 Raw materials are free from iron oxide.
 Porcelain process: Body and glaze in single
firing
China process: Glaze is developed in second
firing.
 Bisque: Porous body of the article dried and
fired in a biscuit oven.

33. Stoneware: strong and hard
 Made from crushed pottery,, clays and stones
fired at high temperatures.
 Used for making sanitary fixtures and
drainage pipes.
 They have high chemical and thermal
resistance and low coefficient for thermal
expansion.
Earthenware: They are made from same
materials fired at low temperature and they
are soft clay products.

34. Structural Clay products:
 They include bricks and tiles made from clay
and sand by moulding, drying and firing.

35.  Glass: It is an amorphous solid ,
transparent, hard and brittle.
 Manufacture of glass: raw materials are soda lime
and silica.
 Calcium carbonate, lead oxide, potassium
carbonate, alumina are added to improve the
quality and yield different types.
 Broken glass called cullet is added to ease the
melting and decrease the cost.
Three process:
I. Melting : Raw materials along with cullet are
ground and fused in furnaces.
Producer gas( CO +N2) and air provide temp. of
about 1800 °C.
Acidic silica + Basic Oxides = Silicates (glass)
II. Forming and shaping: Molten glass is formed and
shaped in desired shapes.

36. Irregular shapes are made by applying pressure to glass of
high viscosity. Moulding is used for making regular
shapes
III. Annealing: controlled slow cooling. Done to avoid strains
and stress built due to differential rates of cooling of
external and internal parts.
Longer the annealing period, better is the glass.
IV. Finishing : Involves cutting, polishing and cleaning.
Properties of glass: Poor conductor of heat and
electricity,
Transparent to light
Homogeneous structure
High compressive strength
Resistant to acids except HF as it forms volatile SiF4 and
silica.I t is used for etching glass.

37. Different types of glass
Soda Lime glass/ Soft Glass: Made from Sodium
silicate, Made insoluble by adding lime. melts at
low temperatures, RESISTANT to devitrification
(Loss of Plasticity and hence to be shaped).
Used in making electric bulbs, wind panes and
cheap table ware.
Borosilicate glass/ Pyrex/Jena Glass: Contains
silica and boron with Al, Na and K oxides in minor
amounts.
Hard glass with low thermal expansion, high
thermal and chemical resistance, high melting
point.

38.  Used in manufacture of laboratory ware, electric
insulators, kitchenware.
Flint glass/ Lead Glass: contains silica, Lead and
potassium oxide.
Soft and easy to grind., high refractive index.
Used in making optical lenses, radiation shields
and neon sign tubes.
Potash-Lime/ Hard Glass: contains silica, Calcium
carbonate and potassium carbonate. High
melting temp. More stable towards chemicals.
Alumina glass: contains 20% of alumina along
with B, Mg and Ca oxide. High softening
temperature.Used in discharge tubes and
combustion tubes.

39.  Vitreosil: 99.5% pure silica glass. Low
coefficient of thermal expansion and highly
transparent. Used in chemical plants and
electric insulators.
 Toughened Glass: obtained by prestressing,
and tempering/thermal strengthening.
Tempering involves heating to its annealing
temp. and rapidly exposing to cold blast of
air. The surface becomes dense and interior
becomes plastic due to difference in cooling
rate. Used in window panes of automobiles.
 Machining of the glass should be done before
tempering.

40.  Safety/ Laminated glass: made by pressing a
sheet of glass in alternate layers of synthetic
rubber. This glass is tough and shatter proof.
The glass pieces donot fly when glass breaks
suddenly. Used in windshields of aircraft.
 Insulating glass: made by hermetically
sealing two glass plates separately by a gap
of about 10 mm thickness filled with air. Used
for thermal insulation against heat.
 Optical glass: highly homogeneous. Consist
of lead silicate, phosphorous and cerium
oxide. Cerium oxide absorbs uv rays harmful
for eyes. Used for making lenses.

41.  Glass ceramic/ Pyroceram: polycrystalline
vitrified glass formed by controlled
crystallisation in nucleating agents such as
TiO2, ZrO2, Cu etc. It has greater hardness
and impact strength as compared to ordinary
glass.

42. Refractories: are inorganic materials
capable of withstanding high temperature. They
resist corrosive and abrasive action. Used in
construction of furnaces and kilns.
Characteristics:
 High resistance to change in physical, chemical
and mechanical properties at high temperatures.
 Chemical inertness to corrosive metals.
 Good thermal strength or resistance to thermal
shocks.
 Resistance to abrasion and erosion by gases or
molten metals.
 Mechanical and structural strength to withstand
load.
 Low permeability or ability to contain heat
without loss to surroundings.

43. Classification of
refractories:
• Eg: Silica or Alumina
Acidic • Are attacked by basic environment
• Eg: CaO Or MgO
Basic • Are attacked by acidic environment
• Carbon, graphite, SiC, ZrO2
• Can withstand slightly acidic and basic
neutral conditions

44. Properties of refractories:
 Chemical inertness: Acidic refractories should be
exposed to acidic and basic refractories should be
exposed to basic environment.
 Refractoriness: Ability to withstand deformation and
is measured by fusion/softening temperature of the
material. Softening temp. is detemined by
Pyrometric cone equivalent(PCE) or seger Cone Test.
Refractory material is ground in form of small, slim
pyramid shaped cone of standard dimensions and
heated at the rate of 10˚C/ min along with standard
seger cones placed on the same plaque.The
softening behaviour is compared with that of
standard by noting the interval of temperature at
which cone starts to bend and the final temperature
at which tip of the cone touches the base.

45.  PCE value of test refractory is taken as the no. of the
standard Seger Cone which shows a similar behaviour.
Thus, it should have a high softening temperature.
 Refractoriness Under Load/ Strength of a refractory:
They should have high mechanical strength to
withstand the load applied, without breaking under
operating temperatures. Fire clay and high alumina
collapse while silica bricks have good load bearing
capacity. Load bearing capacity is evaluated by RUL
test by applying a constant load of 3.5 or 1.75 kg/cm2
on the refractory specimen of size 75 cm high and 5
cm2 and heating at a constant heating rate of 10 C
/min monitoring the deformation. RUL is expressed as
the temp at which 10% deformation takes place.RUL
for a high temp refractory under a constant load of 3.5
kg/cm2 is 1350˚C and for a moderate temp refractory is
1100 ˚C.

46.  Dimensional Stability: It should have high
resistance to reversible and irreversible changes
under operating conditions.Permanent changes
may occur due to fusion of low temperature
fusing constituent resulting in shrinkage of
material as in case of fire clay bricks. Permanent
changes occur due to transformation of one
crystalline form into another and lead to
contraction as in case of magnesite bricks,
whereas silica bricks undergo irreversible
expansion and convert into tridymite .

47. Lubricants:
 Are substances used to reduce friction btwn two
moving surfaces.
 The study of wear and tear, mechanisms of
friction and lubrication is called tribology.
 Irregularities appearing on rough surfaces in the
form of peaks are called asperities.
 Siezure is the prevention of movement of surfaces
due to strong adhesion.
 Scuffing is the removal of metal from the surface
due to forced movement under siezed conditions.

48. Mechanism of lubrication:
 Thin film/ Boundary Lubrication:involves a thin film
adsorbed on surfaces and held by weak forces.
Coefficient of friction is reduced to 0.05-0.15.The
thickness of lubricant is not enough to cover all the
asperities and hence lead to wearing of the
machinery. It occurs due to non availability of
continous film of lubricant. Friction can be prevented
by using lubricant of low shear strength and high
oiliness( vegetable oils).
 Fluid Film/Hydrodynamic Lubrication: involves a
thick film of lubricant and friction is considerably
reduced to a value of 0.001. Since no direct contact
of surfaces is there, no wear takes place. Observed in
sewing machines, guns and scientific instruments.
Hydrocarbon oils with long polymers are useful.

49.  Extreme Pressure Lubrication: involves
chemical action on the part of lubricant.
Under high load and speed resulting in high
temp, lubricant film melts and breaks
completely. Hence spcl additives called
extreme pressure additives are added to
lubricating oils. S, P and Cl containing cmpds
are added. They donot reduce friction but
prevent welding of surfaces. These additives
are not suitable for inert metal surfaces such
as Ag, Cr and Ti.

50. Classification of
lubricants:
 Liquid lubricants: derived from petroleum oils
as well as from animal and vegetable 0ils.
Theey provide continous film btwn moving
surfaces. They also help in cooling, corrosion
inhibition and sealing.
 Characteristics of good lubricant:
 High Boiling pt Thermal stability
 Low freezing point Resistance to corrosion
 Adequate viscosity resistance to oxidation

51. Liquid lubricant consist of
three classes:
 Mineral/petroleum oil: Obtained from distillation of
petroleum(Light, medium and heavy). Wax, asphalt
are present as impurities and hence cannot be used
as such as lubricants as wax has low pour point and
hence interfere with lubricating action. Asphalt also
deposit as carbon and deposit as sludge.
 Purification is done by : solvent extraction,dewaxing
and finishing operations.
 It consist of mixture of parrafins(low viscosity and
density and easily oxidised), napthalenes(low pour
point) and aromatic hydrocarbons((stable to
oxidation but form sludge).

52.  Animal and vegetable oil: glycerides of high
fatty acids and called as fixed oils as they
decompose on heating. They are used as
additives of petroleum oils because of high
oiliness.
 Blended oils: derived from petroleum oils.
Oiliness carriers: vegetable oils(castor or
coconut oil) and fatty acids(palmitic and
stearic acid).
 Pour point depressants: enable the oil to
remain fluid even at low temp. Eg: Phenol
and polyesters.

53.  Viscosity index improvers: are high mol. Wt.
polymers. Eg: Polyisobutylenes and
polymethacrylates.
 Antioxidants: retard the oxidation of oil by getting
themselves oxidised. Eg: 2-napthol, phenyl-1-
napthylamine.
 Corrosion inhibitors: alkyl succinic acids and
organic phosphates.
 Antiwear agents or extreme pressure additives:
tricresyl phosphate(also used as abrasion
inhibitor) and zinc dialkyldithiophosphate.
Detergents(2-10%) are used to prevent deposits
in internal combustion engines.
 Antifoaming agents: glycol and glycerol.

54. Properties of Liquid
lubricants:
 Viscosity: Viscosity decreases with increase in
temperature. A high value of V.I indicates
that viscosity is only slightly affected by
change in temp and vice versa. V.I can be
improved by addition of linear polymers.

55.  Flash and fire point:To determine the use of
lubricating oil at high temp. Flash Point is defined as
lowest temp. at which oil give enough vapours to give
a flash when they come in contact with flame.
 Fire point lowest temp. at which vapours of oil burn
continously at least for 5 sec with test flame.
 Oil should have above its service temp so as to avoid
risk of fire.
 Cloud and pour point: Used in determining the source
of the lubricant.The temperature at which oil becomes
cloudy and solidifies are called cloud and pour point
respectively.Pour point signifies the min. temp. at
whch oil can be transferred by pouring.

56.  Oiliness: ability of oil to stick on the surface. Mineral
oils are poor in oiliness, Hence vegetable oils are
added to mineral oils.
 Volatility: shoul have low volatility as they volatise
leaving behind residual oil having different
characteristics.
 Emulsification: indicates the tendency of oil to get
mixed with water. Water attracts dirt and other
solids and hence it should not form stable emulsion
with water.Steam emulsion temp(S.E.N) is the time
required in seconds to separate water and oil in
distinct layers. Good lubricant should have low
S.E.N.
 Neutralisation no: is the measure of acidic and basic
impurities. Acid value is defined as no. of mg of KOH
required to neutralise acids in 1 g of the oil.Generally
this value is less than 0.1.

57.  Saponification no: is the no. of mg of KOH
required to saponify fatty acids present in 1 g
of the oil.
 Carbon Residue: this value is quite high and
increases on heating of oils. Good lubricant
should have low carbon content.
 Aniline point: indicates possible deterioration
of oil with rubber surfaces. Aromatic
hydrocarbons tend to dissolve rubber and
hence oil should have low aromatic content.
The higher the aniline point, lower is the
aromatic content.
 Ash content: indicates the presence of
materials that cause abrasion and wear.

58.  Corrosion Stability: a good lubricant should not
cause any corrosion to copper strip.
 Decomposition stability: stability of oil towards
oxidation, hydrolysis and pyrolysis.
 Precipitation no: % of asphalt in oil.
 Specific gravity: used for identifying oil from
unknown source.
 Mechanical stability: used for judging the
lubricant under high pressure.

59. Greases:
 Are defined as solid to semi solid dispersion of a
thickening agent in a liquid lubricant. Thickening agent
are metal soaps. Na, Li, Ca or Al soaps are used as
gelling agents.The greases are nemed after the soap
used in their manufacture.
 Calcium /cup grease: prepared by saponifying fatty
acid with Ca hydroxide. Insoluble in water , water
resistant and most commonly used. Can be used upto
70°C.
 Sodium based: higher dropping point. Slightlu soluble
in water. And can not be used under wet
conditions.Used upto 120°C.
 Lithium based: water resistant and stable upto 80°C.

60.  Al based: high wter resistance and high adhesive
characteristics.Used for lubricating chains.
 Axle greases: prepared by addition of lime to
resin and fatty acids. Cheap and used for less
delicate instruments working under high load
and low speed.
Properties of Greases:
Consistency/ yield value: distance in tenths of
millimeter that a standard cone penetrates
vertically into the sample under a load of 150 g,
temp. of 25°c, and time of 5 seconds.
Drop point: is the temp at which it becomes
sufficiently fluid so as the drop of cup falls from
a cup having a hole of specified diameter.

61. Solid lubricants:Both
organic and Inorganic
 Characteristics:
 Strong adhesion to surfaces
 Low Shear strength
 Chemically inert
 Good Thermal conductivity
 Stability at operating temperature
 Graphite and Molybdenum disulphide are most
widely used as they have layered structure. Mica and
boron nitride also have layered structure but are
ineffective as lubricants becase of poor adherence to
surfaces and strong interlayer binding.
 Graphite is used as solid powder in oil less bearings.

62. Choice of Lubricants:
 Properties of Lubricant should not change under
adverse conditions such as fluctuations in
temperature, load and in oxidising or corroding
atmospheres.
 Cutting fluids and emulsions: used where metal and
alloys undergo cutting, machining and grinding
operations. The chosen lubricant is required to
lubricate as well as cool the tool and are called
cutting fluids. They also prevent distortion and
dimensional inaccuracies as they remove unwanted
solid particles.
 For heavy cutting, mineral oils of low viscosity
blended with fatty oils and chlorinated compounds,
called cutting oils are used because they remain
attached to metal surface.

63.  For light cutting, emulsions of lubricating oils in aqueous
soap solutions are used.Oil act as lubricant while water acts
as coolant.
 Lubricants for internal combustion engines: Should have
high thermal stability, oxidation stability as they are exposed
to high temperature. Petroleum based lubricating oils are
used for this.
 Lubricants for gears: should have good oiliness, adhesion,
resistance to oxidation and high load bearing capacity as
high pressure and centrifugal forces prevail in engines.
Mineral oils are used along with chlorine ,soaps, S or P
compounds.
 Lubricants in transformers: should have good dielectric and
heat transfer properties as they have to dissipate heat. Highly
refined mineral oils are used.
 Lubricants for refrigeration: should have low pour point, low
cloud point and low viscosity. Napthalenic based oils are
used.