Cement as a construction material

1. CEMENT

2. GROUP 4
NAME REGISTRATION
NUMBER
COURSE
AHUMUZA AGNES 16/U18656 QS
BAINOMUGISHA GASTON 16/U/4161/PSA QS
KANKIRIHO GODFREY 16/U/5393/PSA QS
MAWANDA ALICIA 16/U/590 QS
OWINO SHELAH RUTH 16/U/1070 QS
AGUDU RACHAEL 16/U/2862/PSA LE
MAKOKO IVAN 16/U/18823 LE
TUMWINE COLLETTE 16/U/1216 LE
KASASA EDRINE FELIX 16/U/5502/PSA CM
LWANGAAARON 16/U/551 CM
TWESIGYE RICHARD 16/U/1231 CM
WAMALA RONALD 16/U/1261 CM

3. A Brief History
Assyrians and Babylonians were probably the first to use
clay as a cementing material.
Vitruvius, a Roman scientist, is believed to be the first to
have the know how about the chemistry of the cementitious
lime..
The most significant incorporation of the Romans was the
use of pozzolan-lime cement by mixing volcanic ash from
the Mt. Vesuvius with lime.
Portland Cement was invented in 1824 by English
stonemason Joseph Aspdin (1778-1855)
Joseph Aspdin

4. Definition
In construction, it is defined as an adhesive agent in mortar and/or
concrete with the ability to unite aggregate particles and
reinforcement into a strong compact consolidated entity.
Cements in a general sense are adhesive and cohesive materials which
are capable of bonding together particles of solid matter into a
compact durable mass.
For civil engineering works, they are restricted to calcareous cements
containing compounds of lime as their chief constituent, its primary
function being to bind the fine (sand) and coarse (grits) aggregate
particles together.

5. Manufacture of Cements
There are basically three broad categories of cement to be
used here;
I. Portland cement (most common)
II. Pozzolan cement ( Roman origin)
III. Natural cements

6. NATURAL CEMENT
Basically any naturally occurring mixture of limestone and
clay
It is also known as;
• Roman cement
• Rosendale cement
• Medina cement
High Bridge over the Harlem River in New York City.

7. Natural Cement
 The composition of the raw materials are similar to those of
Portland cement containing higher proportions of silica and
aluminum.
 One main raw material is Dolostone which is magnesium carbonate
 In the manufacture of natural cement, clinker is never produced
unless it has overburned
 Natural cement is burned at calcining temperatures

8. POZZOLANA CEMENT
Pozzolans are basically a broad category of siliceous and
aluminous materials
They are broadly categorized as;
I. Artificial
II. Natural
Pantheon in Rome

9. POZZOLANS
Natural
 Volcanic Ashes from *Rons in
Italy at Pozzuoli
 Pumice an Igneous rock from
volcanic mountains in Italy,
Germany, Greece and china
Artificial
 Metakolin from thermal activation
of kaolin clays
 Fly ashes from coal-fired electricity
production
 Silica fume from silicon smelting
 Rice husk ash: burned organic
matter rich in silica

10. Pozzolana Cement
Pozzolans have no cementitious values on their own
React with calcium hydroxide in the presence of water
Reaction at room temperature when finely ground
The reaction gives the pozzolans cementitious properties

11. PORTLAND CEMENTS
 The raw materials are;
• Lime, CaO from limestone, chalk, calcite (calcareous rock), shells and
shale
• Silica, SiO2 from sand, old bottles, clay or argillaceous (clay containing)
rocks
• Alumina, Al2O3 from bauxite and recycled aluminum clay
• Iron, Fe2O3 from clay, iron ore, scrap iron and flash ash
• Gypsum, CaSO4.2H2O found in limestone
There are 4 processes of manufacture of Portland cement; wet, semi-wet,
semi-dry and dry. We shall focus on the wet and dry processes.
Calcite rock a.k.a alabaster
Iron oxide pigments

12. Wet Process
 The crushed raw materials are fed into a ball mill with some water.
 Clay is mixed with water to form a slurry.
 Sand is removed by settlement.
 An equivalent slurry is formed with chalk (limestone)
 The two slurries are blended and any coarse materials removed by
screening and the slurries are stored in large slurry tanks.
 The slurries contain about 40% water.

13.  Slurry fed into slow rotating kiln usually 200m long at temperatures of
approx. 1450oC
 The slurry is dried, calcined, and sintered into cement clinker.
NOTE:
 Calcine : to heat something without melting to drive off water and heat limestone to
form quick lime
 Sintering: process in which powder particles are welded together by pressure and heat
 Clinker: hard grey or black lumps or nodules formed during cement manufacture
Manufacture of Portland Cement by the wet process

14. Dry process
This process is adopted when the materials to be used are
hard.
The process is slow
The products are costly.

15. Dry Process
 Limestone (80%), shale (17%) and sand (3%) are crushed and
milled into fine powders then blended.
 The dry meal is preheated at 750oC & calcined at 900oC
 It is then fed into a fast rotating kiln usually 60m at temperatures of
approx. 1450oC.
 Cement clinker is produced.

16. Dry process
 In some industries, the blend of ground raw materials is mixed with
some water.
 Cakes containing 14% moisture are formed and fed into the rotary
kiln.
 Clinker is produced much in the same way as previously explained.
 Ferric oxide acts as flux.
 Aeration of the clinker helps with slaking free lime. The clinker
absorbs some moisture and carbondioxide.
Kiln

17. Final steps
Clinker from both processes is cooled stored.
It is ground (in tube mills) with gypsum (2-3%) to slow
down the setting and prevent rapid flash setting of cement.
Other additives aside from gypsum are added at this stage
to optimize the functionality of the cement.
The final product is stored in silos before being packed
and distributed
Cement clinker
clinker
storage
Gypsum and the secondary additives are added
to the clinker.
Finish grinding

19. Wet process Vs Dry Process
 The wet process has the following advantages;
I. Low cost of excavating and grinding materials
II. Economical use of fuel through the elimination of separated drying
operations.
III.Accurate control of composition and homogeneity of the slurry
 On the opposite side of the coin;
I. The longer kilns used cost more and are less responsive to a
variable clinker demand.

20. Classification of cements
Cements used in construction can be characterized
depending upon the ability of the cement to be used in the
presence of water.
I. Hydraulic cements
II. Non-hydraulic cements

21. Hydraulic Cements
 Hydraulic cement: cement which gains strength in wet conditions
 Hydraulic cement is made by replacing some of the cement in a mix
with activated aluminum silicates, pozzolans, such as fly ash.
 The chemical reaction results in hydrates that are not very water-
soluble and so are quite durable in water and safe from chemical
attack.
 This allows setting in wet condition or underwater and further
protects the hardened material from chemical attack (e.g. Portland
cement).

22. Applications of Hydraulic cement
 Used in swimming pools
 Drainage systems
 Foundations
 Elevator pits
 Basement walls

23. Non-hydraulic cements
Non-hydraulic: cement which gains strength is dry
condition
Non-hydraulic cement will not set in wet conditions or
underwater, rather it sets as it dries and reacts with carbon
dioxide in the air e.g. Plaster of Paris
It can be attacked by some aggressive chemicals after
setting.

24. Non-hydraulic cements
After non-hydraulic cement is utilized in construction, it
must be kept dry in order to gain strength and hold the
structure.
When non-hydraulic cement is used in mortars, those
mortars can set only by drying out, and therefore gain
strength very slowly.
Due to the difficulties associated with waiting long periods
for setting and drying, non-hydraulic cement is rarely
utilized in modern times.

25. Composition
 Primarily composed of limestone or chalk with clay mixed in appropriate
proportion.
 Various additives may be added to give the cement unique properties
 Chemically, it is comprised of Bogue compounds after the name of Bogue
who identified them.
 These compounds are as follows:
 Alite (Tricalcium silicate or C3S)
 Belite (Dicalcium silicate or C2S)
 Celite (Tricalciumalluminate or C3A)
 Felite (Tetracalciumalumino ferrite or C4AF).

26. FUNCTIONS OF CEMENT AND FUCTIONS OF
ITS CONSTITUENT MATERIALS
The main function of cement as a construction material is
to bind fine (sand) and coarse (grit) aggregate together as
it fills voids between fine and coarse aggregate to form a
compact mass.
Raw material ingredients for Portland cement
1. Calcareous materials. The common calcareous materials
are compounds of calcium and magnesium. For example
limestone
2. Argillaceous materials. These are compounds of silica,
alumina and oxides of iron

27. FUNCTIONS OF INGREDIENTS OF
CEMENT
 Lime(CaO)
• It is the major constituent of cement of cement and its proportion
needs to be maintained carefully.
• The lime in excess makes the cement unsound and causes the
cement to expand and disintergrate.
• If lime is in deficiency, the strength of cement is decreased and
cement sets quickly.
• If lime is in right proportion, it makes the cement sound and strong

28.  Silica (SiO2)
 It is an important ingredient of cement and imparts strength to the
cement due to the formation of dicalcium and tricalcium silicates
 Silica in excess provides greater strength to the cement but at tthe
same time prolongs its setting time
 Alimina(Al2O3)
 It imparts quick setting quality to cement
 It acts as a flux and lower the clinkering temperature
 Alumina in excess reduces the strength of cement

29.  Calcium Sulphate (CaSO4)
 It is present in the form of gypsum
 It helps in increasing the initial setting time of cement
 Iron Oxide (Fe2O3)
 It provdes colour, hardness and strength to cement.
 It also helps the fusion of raw materials during manufacture of
cement

30.  Magenesium oxide (MgO).
 This ingredient , if present in small amount , imparts hardness and
colour to the cement
 Magnesium oxide in excess makes the cement unsound
 Sulphur Trioxide (SO3)
 If present in very small quantity, it makes the cement sound
 If present in excess, it causes the cement to become unsound
 Alkalies
 They should be present in small quantities
 Alkalies in excess will cause the efflorescence

31. Harmful constituents of cement
 The following two oxides affect the quality of cement.
 Alkali oxides (K2O and Na2O);
 If the amount of alkali oxides exceeds 1%, it leads to failure of
concrete made from cement
 Magnesium oxide (MgO)
 If the content of magnesium oxide exceeds 5%, it causes cracks after
mortar or concrete hardness

32. Chemical composition of raw materials
 Hydraulic cements constituents are lime, silica and alumina with
addition small proportions of iron oxide, magnesia, Sulphur trioxide
and alkalis
 For Portland cement there has been a change in composition
reflected by the increase in the lime content over the years which
makes it difficult to completely combine with other compounds.
 Free lime exists in clinker and results into an unsound cement.
 Increase in silica content at the expense of alumina and ferric oxides
makes cement difficult to fuse and form clinker

33. Percentage chemical composition of Portland
cement
Lime (calcium oxide and calcium hydroxide) – 60 to 65%
Silica (silicon dioxide) – 17 to 25%
Alumina (aluminium oxide) – 3 to 8%
Magnesia (magnesium oxide) – 1 to 3%
Iron oxide – 0.5 to 6%
Sulphur trioxide – 1 to 2%

34. Effect of each element
 Lime. Controls strength and soundness and its deficiency reduces strength
of cement and quickens its setting. Excess lime makes cement unsound
and causes expansion and disintegration.
 Silica. Imparts strength and in excess it causes slow strength.
 Alumina. Responsible for quick setting, if in excess, it lowers the
strength.
 Magnesia. Imparts colour and hardness. If in excess, it causes cracks in
mortar and concrete and unsoundness.
 Iron oxide. Gives colour and helps in fusion of different ingredients.
 Sulphur trioxide. Makes cement sound.

35. NOTE;
 The rate of setting of cement paste is controlled by regulating the ratio of silica to
alumina plus iron oxide.
 Where development of much heat of hydration is undesirable, the silica content is
increased to about 21% and the alumina and iron oxide contents are limited to 6%
each.
 Resistance to action of sulphate waters is increased by raising further the silica
content to 24% and reducing the alumina and iron contents to 4% each.
 Small percentages of iron oxide renders the highly siliceous raw materials easier
to burn, but if its excess a hard clinker difficult to grind is produced. When iron
oxide combines with lime alone, it promotes instability.
 The alkalis accelerate the setting of cement paste.

36. Clinker
Various constituents combine in burning and form clinker.
 The compounds formed have a setting and hardening
properties in presence of water.
These compounds are known as Bogue compounds and
they include; Tricalcium Silicate, Dicalcium Silicate,
Tricalcium Aluminate, and Tetracalcium Alumino Ferrite

37. Tricalcium silicate (Alite)
 Supposed to be the best cementing material and its well burnt
cement.
 It is about 25 – 50% (normally about 40 %) of cement.
 It renders clinker easier to grind.
 Increases resistance to freezing and thawing.
 Hydrates rapidly generating high heat and develops an early
hardness and strength. However if its content is raised beyond
specified limits, heat of hydration and solubility of cement in water
increases.
 Its hydrolysis is responsible for 7 day strength and hardness.
 Heat of hydration is 500 J/g

38. Dicalcium Silicate (Belite)
 It is about 25 – 40% (normally 32%) of cement
 It hydrates and hardens slowly and takes long time to add to the
strength
 It imparts resistance to chemical attack
 Its rise renders clinker harder to grind, reduces early strength,
decreases resistance to freezing and thawing at early stages and
decreases heat and hydration.
 Its hydrolysis proceeds slowly.
 At early stages, it has little influence on strength and hardness while
after one year it’s contribution to strength and hardness is
proportional to alite.
 Heat of hydration is 260 J/g

39. Tricalcium aluminate (Celite)
 About 5 – 11% (normally 10.5%) of cement.
 Rapidly reacts with water and is responsible for flash set of finely
ground clinker.
 Its rapid action is regulated by addition of 2 – 3% gypsum at the
time of grinding
 It is responsible for the initial set, high heat of hydration and has
greater tendency to volume changes causing cracking.
 Its rise reduces setting time, weakens resistance to sulphate attacks
and lowers ultimate strength, heat of hydration and contraction using
air hardening.
 Heat of hydration is 865 J/g

40. Tetracalcium Alumino Ferrite (Felite)
About 8 – 14% (normally 9%) of cement.
Responsible for flash setting but generates less heat.
Has poorest cementing value.
Its rise reduces strength slightly.
Heat of hydration is 420 J/g

41. Physical properties of cement and their tests
Fineness: Sieve method, Air permeability method, Wagner
Turbidimeter method, Nurse and Blains method and
sedimentation method
Consistency: Consistency test
Setting time: Using Vicat’s apparatus
Soundness test: Le Chatelier’s method, autoclave method
Strength(compressive and tensile): compressive
strength test, briquette test (tensile)
Specific gravity: using Le Chatelier flask
Heat of hydration: using a calorimeter

42. Fineness
 The degree of fineness is the measure of the mean size of grains in
cement.
 The conditions affecting fineness include;
a) Chemical composition
b) Degree of calcination
c) Time of grinding
d) Character of grinding machine
e) Age

43. IMPORTANCE OF FINENESS OF CEMENT
 Finer cement is stronger
 Fine cement has a large surface area for hydration of cement
 Fine cement develops strength earlier with no effect on the ultimate
strength of the paste.
 Strong reaction with alkali reactive aggregates
 Finer cements have increased workability
DISAVANTAGES
 The finer the cement, the more the water required leading to higher
drying shrinkage and cracks.

44. Sieve method
 It measures grain size.
 However, mere grain size does not represent true mean size.
 Cement can consolidate into lumps causing distortion in the final
grain size distribution curve.
PROCEDURE
 Measure 100g of cement sample
 Break lumps with your fingers
 Place the sample in a 90 micron sieve and sieve continuously for 15
minutes
 For OPC, the percentage residue by weight should be 10% and the
specific surface area should not be less than 225m 2/kg

45. Air Permeability method
It is measured in either cm2/g or m2/kg.
It can be measured by Lea & Nurse apparatus / Wagner
turbidimeter

46. Lea & Nurse apparatus (air permeability)
A permeability test cell connected to a manometer and
flowmeter is used.

47. Flowmeter: determination of quantity of air per second
through its capillary tube per unit difference of
temperature.
Manometer: to measure the air pressure
PROCEDURE
20mm height of a sample is placed on a 40 micron plate
Air pressure is applied
The manometer is connected to the top of the air cell and
the air is turned on.

48. The lower end of the air cell is then connected slowly to
the other side of the manometer
Adjust the rate of flow until the manometer shows a
pressure difference (h2) of 30-50 cm. The reading h1 is
recorded.
Repeat until the ratio of h1 to h2 is constant.
Calculate the specific surface.
Minimum for OPC is 2250cm2/g

49. Wagner Turbidimeter (air permeability)
 This is used to estimate the surface area of one grain of cement.
 Cement is dispersed uniformly in a rectangular gas tank filled with
kerosene.
 Parallel light rays are passed through the glass tank and they strike a
photoelectric cell.
 The turbidity is determined from the reading of current from the cell
at a given instant.
 The reading is recorded at particular intervals as the particles fall
into the solution.
 The readings are in cm2/g

50. Consistency test
 To estimate the quantity of water required to form a paste of normal
consistency
 Consistency is defined as the percentage water requirement of a
cement paste
PROCEDURE
 300g of cement added to 25% of water.
 The paste is then filled in the mould of Vicat’s apparatus
 The surface of the paste is smoothened and levelled.

51.  A square needle (10mmx10mm) is attached to
the plunger.
 The plunger is lowered gently over the surface
of the paste and released quickly.
 The plunger pierces the paste.
 The reading on the scale is recorded.
 When the reading is 5-7mm from the bottom,
the amount of water added is considered as the
correct amount for normal consistency.

52. Setting time
 These are the rheological properties of cement
 Setting is the solidification of the plastic cement past.
 There are 2 states of stiffening;
• Initial setting time: this is the time it takes for the cement paste to
begin solidifying. At this point, the paste has become unworkable.
• Final setting time: This is the time after which the needle of Vicat’s
apparatus does not leave any mark.
IMPORTANCE
 It defines the time for handling because useful properties are lost if
cement is placed in the moulds after initial setting time.
 To know when to remove moulds-final setting time

53. Conditions affecting setting time
 Chemical composition of the cement
 Percentage of retardant
 Degree of calcination
 Fineness of grinding
 Aeration subsequent to clinker grinding
 Percentage of water used to make the paste
 Type of cement
 Atmosphere in which the cement paste is placed
 The amount of manipulation the paste receives.
 Conditions of temperature in storage

54. ABNORMAL SETTING BEHAVIOUR
There are two types of abnormal setting which can occur.
False set; this refers to the rapid setting of cement without
the liberation of much heat.
Here, plasticity can be regained by further mixing the
paste without adding water to it.
Flash set; this behavior is accompanied by liberation of
considerable heat.
Its also called the quick set and its not reversible because
in the type of setting, the plasticity cannot be regained by
further mixture of the paste or even addition of water.

55. SETTING TESTS
PROCEDURE
A paste is prepared with 0.85 times the water required for
a paste of standard consistency.
A stop watch is started immediately water is added.
The mould is placed on a non-porous plate, filled
completely with paste and the top is levelled.
This is done at room temperature 270C.

56. The mould is placed in Vicat’s apparatus.
The reading when the plunger is released is recorded.
This is done until the plunger fails to pierce by 5mm
depth.
The reading at this point is the initial setting time.
The cement has finally set when upon applying the needle
gently, it makes an impression but the attachment does not.

57. Soundness test
 Soundness is the ability of a hardened cement paste to retain its
volume after setting without delayed expansion.
 Ideally, concrete should not undergo a large change in volume after
setting.
 This is ensured by limiting quantities of free lime and magnesia.
(they slake slowly causing damage in volume)
 Cement should be allowed to aerate for 2-3 weeks to allow free lime
to hydrate.
 Raw materials finely to ease proportioning and mixing
 Soundness is largely affected by the presence of free lime.
IMPORTANCE

58. Le Chatelier Method
The mould is placed on a glass sheet.
It is filled with a cement paste. 100g of cement with water
0.78 times water required for standard consistency.
It is covered with a glass sheet and a small weight is
placed on top.
The mould is immersed in water at 27-320C
After 24 hours, the distance separating the indicator points
is measured.

59. The mould is submerged again in water that I boiled for 3
hours.
The mould is removed and cooled
The distance between the indicator points is measured
again.
The difference between the two measurements represents
the unsoundness of cement.

60. Determination of strength
 Compressive strength:
 Strength of mortar depends on the nature and type of cement.
 Concrete must develop a particular minimum strength the be used in
construction.
 Concrete is tested for compressive and tensile strengths.
CONDITIONS AFFECTING STRENGTH
I. Fineness of grinding
II. Degree of burning; under burnt cement is likely to be weak
III. Composition
IV. Age

61. Compressive strength: required for mix design.
PROCEDURE
 70.6 mm cubes with 5000 sq. mm surface area for specimen
 Temperature of water and test room should be 270C ± 2
 Dry mix 1:3 of cement and sand with a trowel for one minute
 Water added until the mixture is of uniform color.
 Three specimen cubes prepared
NB: Each should be prepared separately
 Mould is filled completely with paste and set on vibration table
 Impart vibrations for about 2 minutes (12000 per minute)

62.  Cubes removed from moulds and submerged in clean water until
they are taken to the compression testing machine.
 The compressive strength is taken to be the average of the 3 cubes
Tensile strength
 Determined using Briquette’s method or split strength test
IMPORTANCE
 Tensile strength of cement indicates defects in the cement faster than
any other test
BRIQUETTE METHOD
 Cement sand mixture is gauged 1:3 by weight
 (P/5)+2.5 is the percentage of water used. (P is percentage required
to produce a standard consistency)
 Temp of the water and room should be 270C

63.  The mix is filled in moulds of the shape shown.
 An additional heap of mix is placed on the mould and pushed down
with a spatula on either side of the mould.
 The briquettes are finished by smoothing the surface with a trowel
and kept for 24 hours at temp 270C and 90% humidity.
 They are kept in clean fresh water and only taken out for testing
 Six briquettes are tested and their average tensile strength
calculated.
 Load is applied uniformly from zero increasing at a rate of 0.7N/
sq. mm in 12 seconds
 OPC should have a tensile 2.0N/mm2 (3 days) and 2.5 N/mm2 (7
days)

64. SPECIFIC GRAVITY
 This is done using Le Chatelier’s flask
 The flask is filled with either kerosene free of water, or naphtha having a specific
gravity not less than 0.7313 to a point on the stem between zero and 1-ml mark.
 The flask is immersed in a constant temperature water bath and the reading is
recorded.
 A weighed quantity of cement (about 64 g of Portland cement) is then introduced
in small amounts at the same temperature as that of the liquid.
 After introducing all the cement, the stopper is placed in the flask and the flask
rolled in an inclined position, or gently whirled in a horizontal circle, so as to free
the cement from air until no further air bubbles rise to the surface of the liquid.
 The flask is again immersed in the water-bath and the final reading is recorded.
The difference between the first and the final reading represents the volume of
liquid displaced by the weight of the cement used in the test.

66. Chemistry of cement: Hydration
 This is the chemical combination of cement and water to produce a
very hard and strong binding medium for the aggregate particles in
concrete. It’s accompanied by the liberation of heat (heat of
hydration).
 2C3S + 6H C3S2H3 + 3CH
 2C2S + 4H C3S2H3 + CH
 The calcium silicate hydrate (C-S-H gel) forms extremely small
fibrous platy or tibular crystals which can be regarded as a rigid
sponge referred to as cement ‘gel’. Hence it is largely amorphous.

67.  This reaction initially proceeds vigorously forming that dense layer
of the gel which is slightly impermeable and soon prevents more
water from reaching the surface of anhydrous silicate hindering
further hydration due to the protective layer around it.
 The interval of low reactivity (induction period)follows and later
becomes more permeable and hydration picks up.
 However the gel must saturated with water if hydration is to
continue.

68.  Calcium hydroxide partially dissolves in water in damp conditions
to form hydroxyl ions which are important for the protection of steel
in concrete by saturating the cement slurry’s aqueous phase hence
raising its PH between 12.5 and 13. Ca(OH)2 Ca2+ + 2OH-
 The Tricalcium aluminate and Tetra calcium aluminoferrite both
produce calcium aluminate hydrate through intermediate metastable
reactions. 2C3A + 27H C2AH8 + C4AH19 2C3AH6
+ 15H. However the reaction of C3A is responsible for flash setting
of cement (stiffening without strength hardening)

69.  However the hydrates are crystalline hence do not form a protective
layer around the aluminate grain surfaces and therefore rapid
hydration and this the reason gypsum is added .
 CaSO4 Ca2+ + SO4
2-
 These ions from gypsum react with the aluminate and hydroxyl ions
released by the hydrate forming insoluble trisulphoaluminate
(ettringite).

70.  This precipitates as needle shaped crystals on the anhydrous
aluminate grain surfaces hindering further hydration (creating an
artificial induction period).
 Hence hydration of cement considered as a sequence of overlapping
reactions leading to continuous thickening and hardening.
 Gypsum controls setting and hardening of cement but excess of it
leads to an expansion consequent disruption of the set cement paste
and so amount added also carefully watched.

71. NOTE
 During hydration when the anhydrous material is added to water
and products begin to form, the cement grains remain independent
and the cement slurry can be pumped.
 This continues for most of the induction period but when hydration
picks up after the period, the cement grains begin to link together
and the slurry is not pumpable.
 Compressive strength develops as hydration products become inter-
grown.

72. Factors that affect speed of hydration
 Temperature; these reactions speed up as temperature increases.
 Relative concentrations of the cement components; the more
tricalcium silicate there is relative to dicalcium silicate, the quicker
cement sets because tricalcium reacts quicker than dicalcium
silicate.
 Fineness/particle size; this is because the finer the cement, the
more water required to prepare a pumpable slurry and the faster
compressive strength develops.
 Concentration of tricalcium aluminate; cements containing less
amount of it are less susceptible to sulphate attack . Magnesium and
sodium sulphates in down hole brines/saline water or sea water react
with cement hydration products and cause loss of compressive
strength.

73. Chemical properties
 Insoluble residue; fraction of cement is insoluble in hydrochloric
acid. This comes from mainly clay compounds or silica which has
not reacted to form silicate compounds in the rotary kiln. It is a
measure of the completeness of reactions in the kiln thus determines
the amount of unburnt raw material and contamination from
gypsum or storage.
 Loss on ignition (L.O.I); this is the loss of weight of a cement
sample when heated at 1000 degrees Celsius. L.O.I ≤ 3%. Indicates
prehydration or carbonation due to prolonged/improper storage.

74. Chemical properties
 Alkalis; the alkali content of cement is reflected in the amounts of
potassium and sodium oxides. Large amounts can cause certain
difficulties in regulating set times of cement. Limiting volume of
alkali oxides is often specified for cements which are used with
reactive aggregates to prevent alkali-aggregate reaction which
results in disruptive expansion.

75. Chemical properties
 Detrimental/ autoclave expansion; provides an index of potential
delayed expansion caused by the hydration of free MgO and CaO. It
is impossible to tell exactly how much CaO fails to combine into
clinker minerals during the burning process. Calcium oxide that
doesn’t combine is called free lime too much of which can cause
delayed expansion. They show large volume expansion after
hydration resulting in disintegration of hardened concrete.
CaO + H2O Ca(OH)2 (1.32 times volume expansion)
MgO + H2O Mg(OH)2 (1.45 times volume expansion)

76. Chemical properties
 Air content; all cements when mixed with water and sand have a
tendency to entrain air. The air content of concrete is influenced by
many factors including the potential for air entrainment from
cement.
 Sulphur trioxide, SO3 from gypsum; amount of gypsum is
approximated by multiplying amount of sulphur trioxide by 2.15

77. CHEMICAL TESTS
Loss On Ignition
1.00g of the sample is heated for 15 minutes in a weighed and covered
platinum crucible of 20 to 25 ml capacity by placing it in a muffle
furnace at any temperature between 9000C and 10000C. It is then
cooled and weighed. Thereafter, the loss in weight is checked by a
second heating for 5 minutes and reweighing. The loss in the weight is
recorded as in the loss on ignition and the percentage of loss on
ignition to the nearest 0.1 is recorded (loss in weight*100). The
percentage loss on ignition should not exceed 4%.

78. Silica
 0.5g of the sample is kept in an evaporating dish, moistened with 10
ml of distilled water at room temperature to prevent lumping. To this
5 to 10 ml of hydrochloric acid is added and digested with the aid of
a gentle heat and agitation until solution is complete. Dissolution
may be aided by a light pressure with the flattened end of a glass
rod. The solution is evaporated to dryness on a steam bath. Without
heating the residue any further, it is treated with 5 to 10 ml of
hydrochloric acid and then with an equal amount of water. The dish
is covered and digested for 10 minutes on a water bath.

79.  The solution with an equal volume of hot water is diluted and is
immediately filtered through an ashless filter paper, and the
separated silica (SiO2) is washed thoroughly with hot water and the
residue is reserved. The filtrate is again evaporated to dryness,
baking the residue in an oven for an hour at 1050C to 1100C. Then
the residue is added with 10 to 15 ml of hydrochloric acid (1:1) and
is heated on a water bath. This solution is then diluted with an equal
volume of hot water and the small amount of silica it contains is
filtered and washed on another filter paper. The filtrate and washing
are reserved for the determination of combined alumina and the
ferric oxide.

80. The papers containing the residues are transferred to a weighed
platinum crucible. The papers are dried and ignited first at low
heat until the carbon of the filter papers is completely consumed
without inflaming, and finally at 11000C to 12000C until the
weight remains constant (say W1).
The ignited residue thus obtained, impurities is treated in the
crucible with a few drops of distilled water, about 10 ml of
hydroflouric acid and one drop of sulphuric acid and evaporated
cautiously to dryness. Finally, the small residue is heated at
10500C to 11000C for a minute or two: cooled and weighed (say
W2). The difference between this weight and the weight of the
ignited residue represents the amount of silica (W).
Silica(%) = 200(W1-W2)

81. Combined ferric oxide and Alumina
200 ml of the sample from the filtrate reserved in silica test is heated to a boil.
A few drops of bromine water or concentrated nitric acid is added during boiling in
order to oxidize any ferrous ion to the ferric condition. It is then treated with
ammonium hydroxide (1:1), drop wise, until in excess. The solution containing the
precipitates of aluminium and ferric hydroxides is boiled for one minute. The
precipitate is allowed to settle, filtered through an ashless filter paper and washed
with 2% hot ammonium nitrate solution. The filtrate and washings are set aside. The
precipitate is then dissolved in hydrochloric acid (1:3). The solution is diluted to
about 100 ml and the hydroxides are reprecipitated. The solution is filtered and
precipitated with two 10 ml portions of hot ammonium nitrate solution. The filtrate
and washings are then combined with the filtrate set aside and is reserved for the
determination of calcium oxide.

82. The precipitate is placed in a weighed platinum crucible, heated slowly
until the papers are charred, and finally ignited to a constant weight at
10500C and 11000C with care to prevent reduction, and weighed (W1)
as combined alumina and ferric oxide. If silica is suspected to be
carried into the filtrate used for this estimation, the residue in the
crucible is treated with a drop of water, about 5ml of hydroflouric and
a drop of sulphuric acid and is evaporated cautiously to dryness.
Finally, the crucible is heated at 10500C to 11000C for one or two
minutes; cooled and weighed (W2). The difference between this weight
and the weight (W1), represents the amount of residue silica. This
amount is subtracted from the weight of ferric oxide and alumina
found as W1. and the same amount is added to the amount of silica
(W). The ratio of percentages of alumina to iron oxide should not
exceed 0.66.
Combined ferric oxide and alumina (%) = weight of residue *100

83. Ferric oxide
40 ml of cold water is added to 1 g of the sample and while the mixture
is stirred vigorously, 50 ml of hydrochloric acid is added. If necessary,
the solution is heated and cement is ground with a flattened end of a
glass rod until it is evident that cement is completely decomposed. The
solution is heated to a boil and is treated with stannous chloride
solution added drop by drop while stirring, until the solution is
decolorized. A few drops of stannous chloride solution is added in
excess and the solution is cooled to room temperature. Then, 15 ml of a
saturated solution of mercuric chloride and 25 ml of manganese
sulphate solution are added and titrated with standard solution of
potassium permanganate until the permanent pink color is obtained.
Iron as ferric oxide is calculated.

84. Alumina
The calculated weight of ferric oxide and the small amount of silica is
subtracted from the total weight of oxides (W1). The remainder is the
weight of alumina and of small amounts of other reported as alumina.

85.  The combined filtrate reserved in the combined ferric and alumina
test is acidified with hydrochloric acid and evaporated to a volume
of about 100 ml. 40 ml of saturated bromine water is added to the
hot solution and ammonium hydroxide is added until the solution is
distinctly alkaline. The solution is boiled for 5 minutes or more,
making certain that the solution is at all times distinctly allowed to
settle, filtered and washed with hot water. The beaker and filter is
washed once with nitric acid (1:33) and finally with hot water. Any
precipitate (of manganese dioxide) that may be left on the tunnel is
discarded. The filtrate is mixed with hydrochloric and boiled until
all the bromine is expelled. 25 ml of boiling ammonium oxalate
solution is added to the boiling solution.
Calcium oxide

86. The solution is made alkaline with ammonium hydroxide and
brought to boiling, the boiling being continued until the
precipitated calcium oxalate assumes a well defined, granular form.
The precipitate is allowed to stand for about 20 minutes or until it
has settled, filtered and washed moderately with ammonium
oxalate solution (1 g per litre).
The filtrate and washings(W3) are set aside for estimating
magnesia.
The precipitated lime after ignition and heating at 11000C to
12000C is weighed.
The percentage of CaO = weight of residue*200. also,
𝐶𝑎𝑂−0.7𝑆𝑂3
2.8𝑆𝑖𝑂2
+1.2 𝐴𝑙2
𝑂3
+0.65𝐹𝑒2
𝑂3
in percent should be less than 0.66.

87. Magnesia
The filtrate (W3) is acidified with hydrochloric acid and is concentrated to about 150
ml. To this solution, about 10 ml of ammonium hydrogen phosphate solution is added
and the solution is cooled by placing in a beaker of ice water. After cooling,
ammonium hydroxide is added drop by drop while stirring constantly, until the
crystalline magnesium ammonium phosphate begins to form, and the reagent is added
in moderate excess( 5 to 10 percent of the volume of the solution), the stirring being
continued for several minutes. The solution is set aside for at least 16 hours in a cool
atmosphere and then filtered. The precipitate is washed with ammonium nitrate wash
solution (100 g of ammonium nitrate dissolved in water, 200 ml of ammonium
hydroxide added and diluted to 1 litre). It is then charred slowly and the resulting
carbon is burnt carefully. The precipitate is ignited at 11000C to 12000C to constant
weight, taking care to avoid bringing the pyrophosphate to melting.
From the weight of the magnesium pyrophosphate obtained, the magnesia content of
the material taken for the test is calculated.
The percentage of MgO = Weight of residue *72.4.
Free magnesia in cement should be less than 4%

88. Sulphuric anhydride
To 1g of the sample, 25 ml of cold water is added and while the mixture is stirred
vigorously 5 ml of hydrochloric acid. If necessary, the solution is heated and the
material is ground with a flattened end of a glass rod until it is evident that the
decomposition of cement is complete. The solution is diluted to 50 ml and digested
for 15 minutes. The mixture is filtered and the residue washed thoroughly with hot
water.
The filter paper with the residue (W4) is set aside. The filtrate is diluted to 250 ml and
heated to boiling. 10 ml of barium chloride (100 g per litre) solution is added drop by
drop and the boiling is continued until the precipitate is well formed. The solution is
digested on steam bath for 4 hours or overnight. The precipitate is filtered and the
precipitate is washed thoroughly. The filter paper and the contents are placed in a
weighed platinum crucible or porcelain crucible and slowly the paper is incinerated
without inflaming. Then it is ignited at 8000C to 9000C, cooled in a desiccator and the
barium sulphate is weighed. From the weight of the barium sulphate obtained, the
sulphuric anhydride content is calculated.
The percentage of SO3 = Weight of residue*34.3. sulphur in cement should be less
than 25%

89. Insoluble residue
The filter paper containing the residue (W4) is digested in 30 ml of hot
water and 30 ml of 2M sodium carbonate solution maintaining constant
volume, the solution being held for 10 minutes at a temperature just
short should of boiling. It is then filtered and washed with dilute
hydrochloric acid (1:99) and finally with hot water till free from
chlorides. The residue is ignited in a crucible at 9000C to 10000C, in a
desiccator and weighed. The insoluble residues not exceed 1.5%.

90. TYPES OF CEMENT AND THEIR USES
 Ordinary Portland Cement
 OPC air-entraining
 Modified Portland Cement
 MPC air-entraining
 High Early Strength Cement
 High early strength air-entraining
 Low Heat Portland Cement
 White Portland Cement
 High Alumina Cement (HAC)
 Portland Pozzolana Cement
 Portland Blast Furnace Slag Cement
 Masonry Cement
 Natural Cement
 Expansive Cement
 Sulfate Resistant Portland Cement

91. Rapid hardening Portland cement
 It has high lime content and can be obtained by increasing the
tricalcium silicate content but is normally obtained from ordinary
Portland cement clinker by finer grinding.
 The basis of it's application is its hardening properties and heat
emission rather than the setting rate.
 Uses: it is suitable for repair of roads and bridges when load is
applied in a short period of time.

92. High Alumina cement
 It is not a type of Portland cement and is manufactured by fusing
40% bauxite, 15% iron oxide with little of ferric oxide, silica and
magnesia at a very high temperature.
 The resultant product is ground finely.
 Uses: it is resistant to the action of fire, sea water, acidic water and
sulphates and is used as refractory concrete in industries and is used
widely for precasting.

93. SuperSulphated Portland cement
 It is manufactured by inter grinding a mixture of granulated blast
furnace slag not less than 70%, calcium sulphate and small quantity
of ordinary Portland cement.
 Uses: for hydraulic installations and in construction intended for
service in moist conditions.
 Ground water pipes, concrete structures in sulphate bearing soils,
sewers carrying industrial effluents, concretes exposed to sulphates
of weak mineral acids.

94. Sulphate Resisting Portland cement
 The amount of tricalcium aluminate is restricted to an acceptably
low value, less than 5%.
 It is manufactured by grinding and mixing together calcareous and
argillaceous or other silica, alumina and iron oxide bearing materials
which are burnt to a clinkering temperature.
 The resultant clinker is burnt to produce the cement.
 Uses: in conditions where concrete is exposed to the risk of
deterioration due to sulphate attack, sea water concrete, concrete in
contact with soils or ground waters containing excessive sulphate.

95. Portland slag cement
 Manufactured either by uniform blending of portland cement and
finely granulated slag or inter grinding a mixture of portland cement
clinker and granulated slag with addition of gypsum or calcium
sulphate.
 Uses: used in all places as ordinary portland cement but can be used
for mass concreting in dams because of its low heat hydration.

96. Low Heat Portland Cement
Heat is limited by minimizing tricalcium aluminate
component and a high percentage of dicalcium silicate and
tetracalcium alumino ferrite is added.
Uses: suitable for large concrete works such as dams,
large raft foundations.

97. Portland Puzzolana Cement
 Manufactured by grinding Portland cement clinker and puzzolana (
usually fly ash) or by intimately and uniformly blending Portland
cement and fine puzzolana( burnt clay, shale, fly ash).
 Uses: it has a low heat evolution and is used in places of mass
concrete such as dams, and in places of high temperature.

98. Quick Setting Portland Cement
The quantity of gypsum is reduced and small percentages
of aluminum sulphate is added.
 It is ground much finer than ordinary Portland cement.
Uses: it is used when concrete is to be laid under water or
in running water.

99. Water Proof Cement
It is manufactured by adding stearate of calcium and
aluminum treated with tannic acid at the time of grinding.
Uses: water retaining structures like tanks, reservoirs,
retaining walls, swimming pools, bridge piers etc.

100. Water Repellant or hydrophobic Cement
A small amount of surfactants such as stearic acid, boric
acid, or oleic acid is mixed with ordinary portland cement
during grinding of clinker.
Uses: it is most suitable for basements and making water
tight concretes.

101. White and Colored Portland Cement
Manufactured from pure white chalk and clay free from
iron oxide. Colored cements are made by adding 5 to 10%
coloring pigments before grinding.
Uses: used for making terrazzo flooring, face plaster of
walls(stucco), ornamental works and casting stones.

102. Air entraining cement
Vinsol resin or vegetable fats and oils and fatty acids are
ground with ordinary cement.
These materials have the property to entrain air in the form
of fine tiny air bubbles in concrete.
Uses: air entraining cements are used for the same
purposes as ordinary Portland cements.

103. Calcium Chloride Cement
It is also known as extra rapid hardening cement. Made by
adding 2% of calcium chloride. It is highly deliquescent
and so should be stored under dry conditions.
Uses: it is very suitable for cold weathers.

104. Masonry Cements
Many commercial masonry comments are mixtures of
portland cement and pulverized limestone often containing
as much as 50 to 60% limestone.
Uses: used for setting unit masonry such as brick, tile and
stone.

105. Cement additives
An additive is any substance added to some thing in small
quantities, typically to improve or to preserve it
Liquid or powder additives to improve grinding efficiency
, and reduce production costs, and enhance properties of
cement

106. Cement additives
They include;
I. Accelerators
II. Retarders
III. Defoamers
IV. Dispersants
V. Free water and suspension additives
VI. Expansion/ Bond improving additives
VII.Fluid loss control additives
VIII.Gas blocking additives
IX. Spacers and flushers

107. Accelerators
 Cement setting can be adjusted with accelerators .
 They speed up the time required for cement slurry to become hardened
in a reaction that provides faster drill of this reaction process is known
as hydration.
 Accelerators essentially speed the reaction with water , which in turn
reduces the thickening time and causes early compressive strength
development after set .
 Examples
 Potassium chloride
 Calcium chloride

108. Retarders
 Cement setting times can be adjusted with retarders . Cement
retarders control the time when slurry will set hard, keeping the
slurry viscous and pumpable in expected wellbore temperatures and
for the amount of time required to place the slurry
 They decrease the rate of cement hydration, acting in a manner
opposite to that of accelerators
 Examples
 Organic acids
 Cellulose derivates

109. Defoamers
 Defoamers can control or prevent frothing, foaming and air
entrainment in cement slurries that may occur during the mixing
process
 Excessive foaming can cause an underestimation of slurry density
downhole.
 Excessive foam can lead to caveating during mixing, which in turn
may lead to equipment damage and or loss in hydrostatic pressure

110. Dispersants
 Cement slurry flow properties are complicated and do not exemplify
the fluidity of ideal Newtonian fluid behavior.
 The thinning effects of dispersants help modify the slurry for easier
mixing and placement.
 Adding dispersants can lower friction and lower pressure during
pumping, enhance turbulent flow at reduced pumping rates, and allow
operators to mix densified cement slurries
 Dispersants also help to reduce pressure exerted when placing cement
across unconsolidated sands

111. Free water and suspension additives
 Slurry performance can be enhanced with additives that control free
water and prevent solids from settling.
 Free water and suspension additives can help particles and solids in
slurry to remain suspended .
 They also help over come the potential for fluid to develop at the top
of a slurry column or on the high side of deviations in a highly deviated
well or a horizontal well bore

112. Expansion/Bond improving additives
 Special additives are available that can enhance the expansive
properties of various cements. These additives work by way of
crystalline growth or in situ gas generation. Expansive cements expand
slightly after the cement is set . This can help promote bonding
integrity between cement and the casing and the life of the well to
provide the following benefits
 Control gas migration
 Protect casing from corrosive conditions
 Reduce or eliminate un wanted fluid production(water or gas )

113. Fluid loss control additives
 they are added to cement slurries for the following
 To reduce the possibility of dehydration opposite porous zones and
consequently flash setting of the cement
 Loss of fluid from the slurry will result in increasing slurry
viscousity and gradient and higher circulating pressures
 Excessive fluid loss will reduce slurry volume and give less cement
fill

114. Gas blocking additives
 During the hardening process the cement slurry passes through a semi
solid phase in which the liquid has gelled up. As a result the over
burden pressure will be lost thus permitting gas migration into, and
through, cement matrix
 Surfactants added to the slurry will form a stable foam with the gas
bubbles preventing their transport through the cement slurry.
 Additives may be incorporated into the slurry which act to block the
gelled cement pore structure preventing gas migration

115. Spacers and flushers
 Spacers fully displace drilling fluid from the annulus and condition
the casing and annular surface to accept a cement bond .
 Spacers and flushers are intended to displace drilling fluid from the
annulus, leave the casing and formation which is free of oil and
separate drilling fluids from the cement slurry. Thus the spacer is
pumped ahead of the lead cement slurry.
 flushers are used to thin and disperse drilling fluid particles
 If even a thin layer of oil from the drilling fluid is let on the casing
and /or the formation it can prevent the cement slurry from directly
contacting each surface to form a good bond

116. Quality checks for cement on site
 It is necessary to check the quality of cement on site at the time of
preliminary inspection.
 It is not possible to check all the engineering qualities of cement on
site but there exist some field test which gives us a rough idea of
quality of cement.

117. Field test for cement
 Date of packing
 Color
 Rubbing
 Hand Insertion
 Float Test
 Smell Test
 Presence of lumps
 Shape Test
 Strength Test

118.  Date of Packing
Date of manufacture should be seen on the bag. It is important
because the strength of cement reduces with age.
 Color
The cement should be uniform in color. In general the color of
cement is grey with a light greenish shade. The color of cement
gives an indication of excess lime or clay and the degree of burning.
 Rubbing
Take a pinch of cement between fingers and rub it. It should feel
smooth while rubbing. If it is rough, that means adulteration with
sand.

119.  Hand Insertion
Thrust your hand into the cement bag and it should give cool
feeling. It indicates that no hydration reaction is taking place in the
bag.
 Float test
Throw a small quantity of cement in a bucket of water. It should
sink and should not float on the surface.
 Smell Test
Take a pinch of cement and smell it. If the cement contains too
much of pounded clay and silt as an adulterant, the paste will give
an earthy smell.

120.  Presence of Lumps
Open the bag and see that lumps should not be present in the bag.
It will ensure that no setting has taken place.
 Shape Test
Take 100g of cement and make a stiff paste. Prepare a cake with
sharp edges and put on the glass plate. Immerse this plate in water.
Observe that the shape shouldn’t get disturbed while settling. It
should be able to set and attain strength. Cement is capable of
setting under water also and that is why it is also called ‘Hydraulic
Cement’.
 Strength Test
A block of cement 25 mm*25 mm and 200 mm long is prepared
and it is immersed for 7 days in water. It is then placed on supports
15000 mm apart and it is loaded with a weight of 340 N. the block
should not show any sign of failure.

121. STORAGE OF CEMENT
• The storage of cement should be such that no dampness is
allowed to reach the cement either from the ground, walls
or the environment.
• The main equipment for storing cement are the storage
silos.
• Cement is also stored in go downs and warehouses at the
construction site

122. TEMPORARY STORAGE OF CEMENT
 Sometimes cement requirement for a day or two may have to be
stored at the site in the open.
 In such cases, cement bags should be laid on a dry platform made of
wooden planks resting over brick-masonry concrete, dry sand
aggregates raised about 25cm above the ground level.
 The stack must be fully covered ,with polythene sheet and protected
against atmospheric moisture.
 The cover sheets must overlap each other properly.
 This type of storage though should not be adopted in wet conditions.

123. Cement silosTemporary storage

124. CEMENT STORAGE SILOS
 It has a capacity to hold up to 45 metric tones of bulk cement.
 The cement storage silos are the storage containers used in the
construction area for both the storage and distribution of cement
mixtures.
 The silos could be of different shapes and sizes.
 They are used at sites for both handling and storage of cement.

125. ADVANTAGES OF CEMENT STORAGE
SILOS
The cement storage silos come in different sizes and
therefore can be used in big and small construction sites
for storing cement.
The cement storage silos may be temporary or permanent
depending on the construction sites.
The silos have bowlers and its therefore easy to get the
cement fitted into the truck in case of transportation.

126. GUIDELINES ON HOW TO STORE
CEMENT ONSITE
 Store cement in a building which is dry ,leak proof and as moisture
proof as possible.
 There should be a minimum number of windows on the building.
 Stack the cement bags off the floor on wooden planks in such a way
that its about 150mm to 200mm above the floor.
 Maintain a space of 600mm all round between the exterior walls and
the stacks.
 Stack the cement bags close to each other to avoid circulation of air.
 The height of the of the stack should not be more than 10 bags to
prevent the possibility of lumping due to pressure.

127. GUIDELINES ON HOW TO STORE
CEMENT ON SITE
 The width of the stack should not be more than 4 bags length.
 In stacks more than 8 bags high, the cement bags should be arranged
alternately lengthwise and crosswise , so as to tie the stacks together
and avoid toppling.
 Stack the cement bags in such a manner so as to facilitate their
removal in order of how they were received.
 Put labels showing the date of receipt so as to show the age of the
cement.
 Different types of cement must be stored differently.

128. CEMENT GO DOWN AT SITE
In most construction projects, go downs are constructed
for storage of a few days requirement of cement.
The go downs are constructed based on the following
dimensions;
Length of cement bags 70cm(average)
Width of cement bags 35cm(average)
Thickness of cement bags 14cm(average)
Clearance and passages 60cm (average)

129. Arrangement in a go down

130. REQUIREMENTS OF A GO DOWN
 The walls must be plastered and made dump proof.
 The roof must be given an appropriate water proofing treatment.
 The floor must be raised by at least 80cm above the ground level to
prevent inflow of water.
 The flooring must consist of a 15cm thick layer of bricks laid in two
courses over a layer of earth consolidated to a thickness of 15cm
above the ground.
 For further protection, cement bags should be stacked at least 10-20
cm clear above the floor by providing wooden battens.
 If any windows are provided, they should be small and tightly shut
at all times to prevent entry of atmospheric moisture.
 It should be thoroughly dry.

131. SHELF LIFE OF CEMENT
 This depends on the conditions of humidity and temperature under
which the cement has been stored .
 If the container for storage is airtight and has been stored where
temperature and humidity have been carefully controlled, then it can
stay for upto 12 months.
 Bagged cement is not airtight and even if unopened should be used
within a few months.
 Unopened bags might have shelf life of up to six months.

132. EFFECT OF STORAGE ON THE
STRENGTH OF CEMENT
 In spite of the best precautions taken to store cement, its found that
its strength is reduced due to long storage. Effort should be made to
store the cement for lesser periods .
 Cement that has been stored for long periods should be checked
before its used.
PERIOD OF STORAGE RELATIVE STRENGTH(%) AT
28 DAYS
Fresh 100
3 months 80
6 months 70
1 year 60

133. GENERAL USES OF CEMENT
• Cement mortar for Masonry work, plaster and pointing etc.
• Concrete for laying floors, roofs and constructing lintels, beams, weather
shed, stairs, pillars etc.
• Construction for important engineering structures such as bridge, culverts,
dams, tunnels, light house, clocks, etc.
• Construction of water, wells, tennis courts, septic tanks, lamp posts,
telephone cabins etc.
• Making joint for joints, pipes, etc.
• Manufacturing of precast pipes, garden seats, artistically designed wens,
flower posts, etc.
• Preparation of foundation, water tight floors, footpaths, etc.

134. CEMENT FACTORIES IN UGANDA
 We have 3 Cement manufacturing factories in Uganda
namely;
I. Tororo cement
II. Hima cement
III. Kampala cement

135. TORORO CEMENT
 After an extensive feasibility study of Tororo carbonate and
limestone was carried out by building research centers in UK,
Russia and Japan, it was decided that a cement factory be built in
Tororo to utilize the available raw materials
 In December 1952, Uganda Cement Industry was incorporated. It
was later taken over by Uganda Development Corporation (UDC) in
1953.
 The ownership of Tororo cement changed at the end of 1995 to the
present owners under the Government Privatization Scheme
 It is the largest manufacturer of cement in Uganda producing an
estimated 1.8 million metric tonnes annually

136. HIMA CEMENT
 It was founded in 1994 and it is wholly owned by Lafarge , the
construction materials manufacturer based in France.
 It is the second largest manufacturer of cement in Uganda after
Tororo cement with an estimated production of 850000 metric
tonnes
 Its vision is to be the preferred provider of cement and concrete
based building solutions in East Africa with a strong focus on
construction experience

137. KAMPALA CEMENT
 It was started in 2015 and it's found in Namataba Mukono
 The plant has installed capacity of one million tons of cement under
brand names of Nyate 32-5, Kifaru 42-5 , Ndovu 42-5 and
Supercrete 52-5
 The plant runs continously throughout the year with little
maintenance done due to latest developed grinding plants imported
from Europe
 Before raw materials are dispatched from the source, they are first
tested and certified
 Its vision is to be a model cement manufacturing company ,
benefiting customers, shareholders and fulfilling corporate social
responsibility while enjoying citizens' respect and goodwill

138. REFERENCES
 Lyons, A. (2010). Materials for Architects & Builders (4th ed.). Oxford: Butterworth-
Heinemann Elsevier Ltd.
 www.engr.psu.edu/ce/courses/ce584/Composition%20of%20cement.html11/09/2017
 Marshall, P. C. (n.d.). Natural Cements. Retrieved from Philip Marshall :
http://www.philipmarshall.net 11 September 2017
 Macfadyen, J.D., 2006: Cement and cement raw materials. Pages 1121-1136 in Industrial
Minerals and Rocks 7th edition. Edited by J.E. Kogel, N.C., Trivedi, J.M. Barker & S.T.
Krudowski. Littleton, Colorado: SME
 Kanuti, A.,2017: Common Building Materials; CEMENT ppt

139. REFERENCES
 http://www.encyclopedia.com/education/dictionaries-thesauruses-pictures-and-press-releases/opus-
caementicium 06/09/2017
 WFM, T. (2016, August 25). WFM Construction Industry Marketplace. Retrieved September 18, 2017, from
https://www.wfm.co.in/hydraulic-cement-vs-non-hydraulic-cement/
 Sini, J. (2012, February 27). Materials in civil engineering. Retrieved September 18, 2017, from The Cutest
Blog on the Block: http://groupc20112012.blogspot.ug/
 Suryakanta. (2015, February 6). How to check the quality of cement on site? Retrieved September 18, 2017,
from CivilBlog.org: http://civilblog.org/2015/02/06/how-to-check-quality-of-cement-on-site/
 Duggal, S. (2008). Building Materials (3rd ed.). New Dehli: New Age International (P) Ltd.