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Building and Road Materials
By: Saqib Imran
Assala mu alykum My Name is saqib imran and I am the
student of b.tech (civil) in sarhad univeristy of
science and technology peshawer.
I have written this notes by different websites and
some by self and prepare it for the student and also
for engineer who work on field to get some knowledge
from it.
I hope you all students may like it.
Remember me in your pray, allah bless me and all of
you friends.
If u have any confusion in this notes contact me on my
gmail id: Saqibimran43@gmail.com
or text me on 0341-7549889.
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Saqib imran.
What is a construction material?
A construction material is any material used in the construction industry.
Examples: Concrete, cement, soil, stones, aggregates, plastics, and
asphalt.
The basic materials used in civil engineering applications or in construction
projects are:
Wood
Cement and concrete
Bitumen and bituminous materials
Structural clay and concrete units
Reinforcing and structural steels
Advantages of Natural Seasoning of Wood
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There are many reasons for drying wood. Four main reasons include:
To increase dimensional stability. Wood shrinks across the grain (not along the
grain) when it dries. If wood is cut to size before it is seasoned, it will shrink during
drying and thus be undersized in its final form.
To reduce or eliminate attack by decay or stain. Wood that is dried below 20 percent
moisture content is not susceptible to decay or sap staining.
To reduce the weight. The weight of lumber will be reduced by 35 percent or more
by removing most of the water in the wood or, as we say, by "seasoning."
To increase the strength. As wood dries, the stiffness, hardness and strength of the wood
increases. Most species of wood increase their strength characteristics by 50 percent or
more during the process of drying to 15 percent moisture content.
When and Where to use the Different Types of Paints
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Sealers
Sealers are applied to unpainted surfaces to
Stop stains and marks from bleeding through topcoats
For oily or smokey stains leg on ceilings use an acrylic stain sealer
For water stains use an oil-based sealer
Already painted surfaces don't need a sealer unless stained
Stop bare surfaces absorbing too much topcoat
For new plasterboard use an acrylic wallboard sealer
For new timber use an acrylic Primer/Sealer
For fibrous plaster use an oil-based sealer
In moist areas always use an oil-based sealer
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What is the Purpose of Applying Paints?
Paints may be used for many purposes. The main purposes of paint are to provide:
Decoration to Interiors and Exteriors of a
Building
They are used to enhance the interior and exterior of a building by adding pigments,
lightness or darkness
Reflective surfaces can be also be obtained
Now a days textures are also added for different designs
Protective Layer
Paint are used to protect the outer surfaces of a building or metals to protect them against:
Sunlight
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Dampness
Dust
Abrasion
Weathering
Ease of Cleaning
To provide easily cleanable surfaces
To keep the substrates clean and tidy
Composition of Ordinary Portland Cement
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Composition of Ordinary Portland Cement
The chief chemical components of ordinary Portland cement are:
1. Calcium
2. Silica
3. Alumina
4. Iron
Calcium is usually derived from limestone, marl or chalk while silica, alumina and iron
come from the sands, clays & iron ores. Other raw materials may include shale, shells and
industrial byproducts.
Basic Composition:
Contents %
CaO 60-67
SiO2 17-25
Al2O3 3-8
Fe2O3 0.5-6.0
MgO 0.5-4.0
Alkalis 0.3-1.2
SO3 2.0-3.5
The chief compound which usually form in process of mixing:
1-triclcium silicate (3CaO.SiO2)
2-Dicalcium silicate (2CaO.SiO2)
3-tricalcium aluminates (3CaO.Al2O3)
4-tetracalcium aluminoferrite (4CaO.Al2O3.Fe2O3)
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Environmental Impact of Ordinary Portland Cement
There are lots of environmental impacts of Cement on our ecology. One of the major
problems is emission of CO2 from the Cement industry. It is found that world yearly 1.6
billion tons production of cement covers 7% of carbon dioxide's yearly production. As
CO2 is harmful for human health and also for the wild life. It causes many respiratory
problems like asthma, bronchitis, and nasal infections.
The cement manufacturing industry is labor intensive and uses large scale and potentially
hazardous manufacturing processes. The industry experiences accident rates that are high
compared with some other manufacturing industries. There are a number of hazards
inherent to the cement production process. Some examples for health hazards are:
1. Exposure to dust and high temperatures;
2. Contact with allergic substances; and
3. Noise exposure
And some examples for safety hazards:
1. Falling / impact with objects
2. Hot surface burns
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Tests Applied on Bitumen in Roads for Quality
Construction
Experience in using bitumen in engineering projects has led to the adoption of certain test
procedures that are indicative of the characteristics that identify adequate performance
levels. Some of the tests have evolved with the development of the industry and are
empirical methods. Consequently it is essential that they are carried out in strict
compliance with the recommended procedures if they are to be accurate measurements of
the bitumen's properties.
1. Penetration Test
2. Flash Point Test
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3. Solubility Test
4. Ductility Test
5. Viscosity Test
Test 1. Penetration Test on Bitumen
The penetration test is one of the oldest and most commonly used tests on asphalt
cements or residues from distillation of asphalt cutbacks or emulsions. The standardized
procedure for this test can be found in ASTM D5 [ASTM, 2001]. It is an empirical test
that measures the consistency (hardness) of an asphalt at a specified test condition.
Procedure of Penetration Test on Bitumen:
In the standard test condition, a standard needle of a total load of 100 g is applied to the
surface of an asphalt or Liquid bitumen sample at a temperature of 25 °C for 5 seconds.
The amount of penetration of the needle at the end of 5 seconds is measured in units of
0.1 mm (or penetration unit). A softer asphalt will have a higher penetration, while
a harder asphalt will have a lower penetration. Other test conditions that have been
used include
1. 0 °C, 200 g, 60 sec., and
2. 46 °C, 50 g, 5 sec.
The penetration test can be used to designate grades of asphalt cement, and to measure
changes in hardness due to age hardening or changes in temperature.
Test 2. Flash Point Test on asphalt:
The flash point test determines the temperature to which an asphalt can be safely heated
in the presence of an open flame. The test is performed by heating an asphalt sample in
an open cup at a specified rate and determining the temperature at which a small flame
passing over the surface of the cup will cause the vapors from the asphalt sample
temporarily to ignite or flash. The commonly used flash point test methods include
1. The Cleveland Open Cup (ASTM D92)
2. Tag Open Cup (ASTM D1310).
The Cleveland Open-Cup method is used on asphalt cements or asphalts with relatively
higher flash points, while the Tag Open-Cup method is used on cutback asphalts or
asphalts with flash points of less than 79 °C. Minimum flash point requirements are
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included in the specifications for asphalt cements for safety reasons. Flash point tests
can also be used to detect contaminating materialssuch as gasoline or kerosine in an
asphalt cement. Contamination of an asphalt cement by such materials can be indicated
by a substantial drop in flash point.
When the flash point test is used to detect contaminating materials, the Pensky-Martens
Closed Tester method (ASTM D93), which tends to give more indicative results, is
normally used. In recent years, the flash point test results have been related to the
hardening potential of asphalt. An asphalt with a high flash point is more likely to have a
lower hardening potential in the field.
Test 3. Solubility Test on asphalt bitumen
Asphalt consists primarily of bitumens, which are high-molecular-weight hydrocarbons
soluble in carbon disulfide. The bitumen content of a bituminous material is measured by
means of its solubility in carbon disulfide.
Procedure for Solubility test on Bitumen
In the standard test for bitumen content (ASTM D4), a small sample of about 2 g of the
asphalt is dissolved in 100 ml of carbon disulfide and the solution is filtered through a
filtering mat in a filtering crucible. The material retained on the filter is then dried and
weighed, and used to calculate the bitumen content as a percentage of the weight of the
original asphalt. Due to the extreme flammability of carbon disulfide, solubility in
trichloroethylene, rather than solubility in carbon disulfide, is usually used in asphalt
cement specifications. The standard solubility test using trichloroethylene is
designated as ASTM D 2042.
The solubility test is used to detect contamination in asphalt cement. Specifications for
asphalt cements normally require a minimum solubility in trichloroethylene of 99.0
percent.
Unfortunately, trichloroethylene has been identified as a carcinogen and contributing to
the depletion of the earth’s ozone layer. The use of trichloroethylene will most likely be
banned in the near future. There is a need to use a less hazardous and non-chlorinated
solvent for this purpose. Results of several investigations have indicated that the solvent
n-Propyl Bromide appears to be a feasible alternative to trichloroethylene for use in this
application.
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Test 4. Ductility Test on Asphalt
The ductility test (ASTM D113) measures the distance a standard asphalt sample will
stretch without breaking under a standard testing condition (5 cm/min at 25 °C). It is
generally considered that an asphalt with a very low ductility will have poor adhesive
properties and thus poor performance in service. Specifications for asphalt cements
normally contain requirements for minimum ductility.
Test 5. Viscosity Tests on Bitumen Asphalt
The viscosity test measures the viscosity of an asphalt. Both the viscosity test and the
penetration test measure the consistency of an asphalt at some specified temperatures and
are used to designate grades of asphalts. The advantage of using the viscosity test as
compared with the penetration test is that the viscosity test measures a fundamental
physical property rather than an empirical value. Viscosity is defined as the ratio between
the applied shear stress and induced shear rate of a fluid.
Shear Rate = Shear Stress / Viscosity
When shear rate is expressed in units of 1/sec. and shear stress in units of Pascal,
viscosity will be in units of Pascal-seconds. One Pascal-second is equal to 10 Poises. The
lower the viscosity of an asphalt, the faster the asphalt will flow under the same
stress. For a Newtonian fluid, the relationship between shear stress and shear rate is
linear, and thus the viscosity is constant at different shear rates or shear stress.
However, for a non-Newtonian fluid, the relationship between shear stress and shear
rate is not linear, and thus the apparent viscosity will change as the shear rate or
shear stress changes.
Asphalts tend to behave as slightly non-Newtonian fluids, especially at lower
temperatures. When different methods are used to measure the viscosity of an asphalt, the
test results might be significantly different, since the different methods might be
measuring the viscosity at different shear rates. It is thus very important to indicate the
test method used when viscosity results are presented.
The most commonly used viscosity test on asphalt cements is the Absolute Viscosity Test
by Vacuum Capillary Viscometer (ASTM D2171).
The standard test temperature is 60 °C. The absolute viscosity test measures the viscosity
in units of Poise. The viscosity at 60 °C represents the viscosity of the asphalt at the
maximum temperature a pavement is likely to experience in most parts of the U.S. When
the viscosity of an asphalt at a higher temperature (such as 135 °C) is to be determined,
the most commonly-used test is the Kinematic Viscosity Test (ASTM D2170), which
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measures the kinematic viscosity in units of Stokes or centi-Stokes. Kinematic viscosity
is defined as: When viscosity is in units of Poise and density in units of g/cm3
the
kinematic viscosity will be in units of Stokes. To convert from kinematic viscosity (in
units of Stokes) to absolute viscosity (in units of Poises), one simply multiplies the
number of Stokes by the density in units of g/cm3
.
Applications & Uses of Building Stones in Civil
Engineering
Uses of stones:
Sandstone is a popular stone with sculptors.
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Good and durable construction material
Thresholds and steps in manor houses
War memorials in the 19th
and 20th
centuries
Limestone for burning lime and also for manufacture of cement
Limestone as a flux in blast furnaces
Insulators in electrical appliances
Building Stones:
Millions of tones of crushed rock are needed annually for road base, paving, ready-
mixed concrete and asphalt.
Sandstone which is not so hard-wearing or beautifully patterned is used for garden
walls and paths in landscaping.
Basalt: It is quarried and crushed as "Blue Metal" which is used as a road-base, and
in reinforced concrete as aggregate.
Although wood, straw and mud is used for houses in some parts of the world, most
buildings are preferred to be built of stones.
Building wells.
Material for foundation and walling of buildings, dams, bridges, etc.
Aggregate
Stone walls
Roof tile in the form of slates
Murram for covering and flooring of road surface
Limestone for burning lime and for the manufacture of Portland cement
Shale is a component of bricks and may also be used in manufacturing of cement.
Nite, another stone type is used for architectural construction, ornamental stones
and monuments.
Marble is widely used in construction industry, for aesthetic purposes, beautification
and strength
Stone being so important in the light of the above uses still is not widely used in
construction. The reasons are:
Stones are replaced by the increased use of RCC. Dressing of stones is time consuming
Stones are not cheaply and conveniently available in plain areas.
Properties of Stones and Tests Applied on Stones
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Properties of Stones
Strength & Durability:
The more compact grained and heavier a stone the harder it is. Due to alternate wetting
and drying the resulting crushing strength can be reduced even up to 30-40%. Being dry
stones allow more crushing strength than when wet.
Stone Weight in lb/cu. ft Ultimate strength to resist
crushing lbs/sq. in
Granite 165 13000
Basalt or Trap 185 12000
Limestone 160 7500
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Sandstone (stray) 140 5000
Slate 175 10000
Marble 170 7500
Table showing the relationship between weights and crushing strength.
It is the ability of a stone to endure and maintain its essential and distinctive
characteristics i.e. resistance to decay, strength and appearance. Physical properties such
as density, compressive strength and porosity are measured in order to determine its
durability. Durability is based upon the stones natural physical properties, characteristics
and the environmental conditions to which it will be or is subjected too. Another factor of
stones durability is its Aesthetic Durability or Dimensional Stability. Cosmetic changes
may occur. This has to do with the Color Stability of certain stones. These changes can
take place in two ways.
SUNLIGHT:
When some stones are used in exterior applications and exposed to direct sunlight they
fade or change color. Dark colored stones and those that contain organic matter will
generally fade to a much lighter color. The Coral stone being of a biogenic origin
contains organic material that will be affected by ultraviolet exposure.
MOISTURE:
Some stones have moisture sensitive mineral contents that will cause the stone to develop
rust spots, or other color variations, or contain moisture sensitive substances that will
cause blotchy and streaking discolorations. Certain lime stones contain bituminous
materials that are soluble when exposed to moisture. Some marbles are also moisture
sensitive when in high moisture areas, showers and those with steam features; these
stones have a tendency to develop dark botches.
Porosity & Permeability:
Porosity is the ratio of pores (micro-voids) in the stone, to its total solid volume. Pores
and the capillary structure develop differently in each of the three stone groups. Dense
and compact stones have very few or no pores in them. An important feature of
sedimentary rocks is their porosity. Pores are natural holes in the stones which allow
fluids like rainwater to enter and leave the fabric. Some free fluid flow through a rock is
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necessary to maintain the rock's durability, and it is not always advisable to block such
flow by using incorrect mortar mixes or by injecting unsuitable synthetic fluids.
Very high porosities, however, may allow excessive volumes of corrosive fluids such as
acid rainwater to enter and cause severe damage to the rock. Thin section rock analysis
can identify where such problems are likely to occur. Most durable sedimentary building
stones commonly have moderate porosity.
Associated with stones porosity is its permeability. This is the extent to which the pores
and capillary structures are interconnected throughout the stone. These networks, their
size, structure and orientation affect the degree and depth to which moisture, vapors and
liquids can be absorb into the interior of the stone or migrate from the substrate by
capillary action through the stone.
Permeability is increased when a stone is highly fractured or the veining material is soft
or grainy. A particular variety of stone may be highly permeable (a well defined
interconnected network of pores), although its porosity is low (a low percentage of
voids).
The size and shapes of pores and the capillary structure differs in stones and is an
important factor in relation to stone decay.
Color, Surface Texture and Veining:
Hardness & weathering:
Hardness is the property of a material to avoid and resist scratching. It is determined by
comparison with the standard minerals of the Moh’s scale. The objective of the MOH
Scale is to measure stones resistance to hardness.
Measurement of Hardness:
1. Talc
2. Gypsum
3. Calcite (Most Marbles)
4. Fluorite
5. Apatite
6. Feldspar (Granite)
7. Quartz (Granite)
8. Topaz
9. Corundum
10.Diamond
Weathering
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It is a complex interaction of physical, chemical and biological processes that alters the
stone in some general or specific way. The physical properties of stone differs widely
between stone groups and even within the same stone type.
The mineral composition, textural differences, varying degrees of hardness and
pore/capillary structure are the main reasons why stone nor all the surface of the same
stone shows signs of alteration the same and evenly. These minerals can be broken down,
dissolved or converted to new minerals by a variety of processes which are grouped as
Mechanical and Chemical. Intensity and duration are two key elements that govern to
what extent weathering reactions will have on stone.
Water absorption and frost resistance:
Moisture from rain, snow or other environmental conditions penetrates the wall leading
to cracks, efflorescence, rust staining, wood rotting, paint peeling, darkening of masonry
and spalling. The perfect sealing of a masonry wall surface is almost impossible since
fine cracks and joints will allow the passage of water into the wall.
Absorbency:
It is the result of these two properties (permeability and porosity). Absorbency is an
important determining factor in stones sensitivity to stains. The size of the pores, their
orientation, how well they are networked and the type of finish the stone has are
important contributing factors to a stones overall absorbency. In relation to cleanability
this factor is more important than how porous a stone is. Honed and textured surfaces are
more susceptible to soiling and staining due to the fact that there are more open pores at
the surface than a highly polished finish.
The polishing process has a tendency to close off pores leaving fewer ones exposed,
resulting in a low absorbent surface. However, some varieties of stone have large pores
and capillary structures and even when these stones are polished they still remain very
absorbent. Most common oils can be easily absorbed into all types of stone.
Frost action or commonly called freeze/thaw cycles occur when water within the pore
structure or cracks freezes to ice. It has been estimated when water freezes it expands
between 8 to 11 percent, with a force of 2,000 pounds per square inch to 150 tons per
square foot. This increase of internal pressure combined with repeated freeze/thaw cycles
produces micro-fissures, cracks, flaking and spalling.
Tests on Stones
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Once a stone has been selected on aesthetic basis, it is important than to ensure whether it
exhibits the necessary physical properties and durability to remain in working condition
for a long time. Fixing method adopted for the construction of stones also affects the type
of stones selected. Physical properties such as density, compressive strength and porosity
are measured in order to determine its durability.
Geological Classification and Characteristics of
Stones
Geologically the stones can be classified as follows:
1) Sedimentary stones:
(a) Characteristics:
Sandstone, limestone, dolomite originally formed mainly in sea water, or lakes, from the
remains of animals and plants, also from transportation and deposition of rock products.
A. Formed at or near the surface
B. Distinctive strata
C. Many fossils have been found in this type of rock
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Grain shape
A. Rounded
B. Angular
(b) Classification of Sedimentary Stones:
A. Detrital is made from disintegrated pre-existing rock.
B. Biogenetic is made from shells and other fossilized fragments.
C. Chemical is made from chemical precipitation.
2) Metamorphic stones:
(a) Characteristics of Metamorphic Stones:
Marble, serpentine, onyx, slate, quartzite, gneiss are produced from sedimentary or
igneous rocks by the action of heat and pressure.
A. No pressure - fossils survive
B. Low pressure - fossils distorted or destroyed
C. Moderate pressure - Grains form moderately
D. High pressure - Active fluids may circulate
E. Heat alone, Metamorphic Aureole surrounding a deep plutonic intrusions, possibly
with active fluids
F. Dynamic Meta - Large scale movement phenomena
G. Crushing actions produce Xylonite Meta rock from powder
H. Low angle thrust fault: Plate pressure coupled with subsidence
I. Thrust movement, plate movement
(b) Classification of Metamorphic Stones:
1. Structure
A. Contact type is crystalline
B. Regional type is usually foliated
2. Grain size
A. +0 Big grain, High pressure
B. 00 Med grain, Med pressure
C. -o Small grain, Low pressure
3. Basic PSI and temperature:
Basic PSI and temperature of occurrence is 480* F - 1472* F 2,000 - 10,000 K
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3) Igneous stones:
These stones are formed when the magma from the earth cools inside the earth or on the
earth surface.
(a) Characteristics of Igneous Stones:
A. Intrusive - subsurface crystallization
B. Extrusive- above surface crystallization
*note Temperature and time has alot of effect on crystal sizes i.e.: Heat + time = Larger
crystal
Igneous form occurrence below ground presents itself in 2 basic ways:
Intrusive basic dike, which is like having layers of cardboard over your head and
punching your fist up into it. Plutonic, this is like a huge hot ball of stone burning its way
around deep below the surface and it usually has "hot arms" that reach out from its main
mass. Crystal habit can successfully delineate a Igneous stones origin, usually. Dikes are
cooler thus forming smaller crystals and Plutons are hotter thus forming larger crystals.
C. Mineral content
D. Grain size, Plutonic >3/16" coarse. Extrusive 1/64" - 3/16" Medium and < 1/64" fine
E. Crystal shape
F. Texture % A, %B, crystal angle.
G. Color
(c) Classification of Igneous Stones:
A. Acid rocks > 65% Si + > 10% Modal Quartz
B. Intermediate rocks 55% - 65% Si
C. Basic rocks 45% - 55% Si < 10% Modal Quartz
D. Ultra-Basic < 45% Si.
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Lab Report of Los Angeles Abrasion Test on a Given
Sample
(AASHTO DESIGNATION: T-96 | ASTM C 131)
The Los Angeles test is a measure of degradation of mineral aggregates of standard
gradings resulting from a combination of actions including abrasion or attrition, impact,
and grinding in a rotating steel drum containing a specified number of steel spheres. The
Los Angeles (L.A.) abrasion test is a common test method used to indicate aggregate
toughness and abrasion characteristics. Aggregate abrasion characteristics are important
because the constituent aggregate in HMA must resist crushing, degradation and
disintegration in order to produce a high quality HMA.
Apparatus:
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Steel Spherical Balls
Machine (The machine is equipped with a counter. The machine shall consist of hollow
steel cylinder closed at both ends. An opening in cylinder shall be provided for
introducing the sample
Sieves
Aggregate used in highway pavement should be hard and must resist wear due to the
loading from compaction equipment, the polishing effect of traffic and the internal
abrasion effect.
The road aggregate should be hard enough to resist the abrasion of aggregate. Resistance
to abrasion is determined in laboratory by loss angles abrasion test.
Principle of the Test:
To produce the abrasive action by use of standard
steel balls which when mixed with the aggregate
and rotated in a drum for specific number of
revolution cause impact on aggregate. The %age
wear due to rubbing with steel balls is determined
and is known as abrasion value.
Prepare the sample by the portion of an aggregate
sample retained on the 1.70 mm (No. 12) sieve and
place in a large rotating drum that contains a shelf
plate attached to the outer wall.
Procedure of the LA Abrasion Test:
Prepared sample is placed in the abrasion-testing machine.
A specified number of steel spheres are then placed in the machine and the drum is rotated
for 500 revolutions at a speed of 30 - 33 revolutions per minute (RPM).
The material is then separated into material passing the 1.70 mm (No. 12) sieve and
material retained on the 1.70 mm (No. 12) sieve.
Dry the sample in an oven.
Calculate %age loss due to Abrasion by calculating the difference between the retained
material (larger particles) compared to the original sample weight. The difference in weight
is reported as a percent of the original weight and called the "percent loss".
Test Sample :
Sample shall be washed and oven-dried at a temperature of 105°C - 110°C and should
conform to one of the grading in observation.
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The L.A. Abrasion test is an empirical test; it is not directly related to field performance of
aggregates. Field observations generally do not show a good relationship between L.A.
abrasion values and field performance. L.A. abrasion loss is unable to predict field
performance. Specifically, the test may not be satisfactory for some types of aggregates.
Some aggregates, such as slag and some limestones, tend to have high LA. abrasion loss
but perform adequately in the field. L.A. abrasion loss seems to be reasonable well
correlated with dust formation during handling and HMA production in that aggregates
with higher LA. abrasion loss values typically generate more of dust.
Uses & Significance of LA Abrasion Test :
1. For an aggregate to perform satisfactory in pavement, it must be sufficiently hard to resist
the abrasive effect of traffic over long period of time. The soft aggregates will be quickly
ground to dust, whilst the hard aggregates are quite resistant to crushing effect.
2. The test also will determine the quality of the aggregate.
3. The L.A. Abrasion test is widely used as an indicator of the relative quality or competence
of mineral aggregates.
Standard Test Methods are:
AASHTO T 96 and ASTM C 131: Resistance to Degradation of Small-Size
Coarse Aggregate by Abrasion and Impact in the Los Angeles Machine
ASTM C 535: Resistance to Degradation of Large-Size Coarse Aggregate by
Abrasion and Impact in the Los Angeles Machine
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To Perform Penetration Test on Bitumen
(AASHTO DESIGNATION: T-49)
In this test we examine the consistency of a sample of bitumen by determining the
distance in tenths of a millimetre that a standard needle vertically penetrates the bitumen
specimen under known conditions of loading, time and temperature. This is the most
widely used method of measuring the consistency of a bituminous material at a given
temperature. It is a means of classification rather than a measure of quality.
APPARATUS:
Penetration Apparatus
Needle
Container
Water Bath
Thermometer for Water Bath
Stop watch
Principle:
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It measures the hardness or softness of bitumen by measuring the depth in tenths of a
millimeter to which a standard
loaded needle will penetrate
vertically in 5 seconds.
PROCEDURE:
Heat the sample until it becomes
fluid.
Pour it in a container to a depth
such that when cooled, the depth of sample is at least 10mm greater than the expected
penetration.
Allow it to cool in an atmospheric temperature.
Clean the needle and place a weight above the needle.
Use the water bath to maintain the temperature of specimen.
Mount the needle on bitumen, such that it should just touch the surface of bitumen.
Then start the stop watch and allow the penetration needle to penetrate freely at same
time for 5 seconds. After 5 seconds stop the penetration.
Result will be the grade of bitumen.
Take at least three reading.
USES AND SIGNIFICANCE:
Penetration test is used to measure the consistency of bitumen, so that they can be
classified into standard grades. Greater value of penetration indicates softer consistency.
Generally higher penetration bitumen is preferred for use in cold climate and smaller
penetration bitumen is used in hot climate areas.
It measures the hardness or softness of bitumen by measuring the depth in tenths of a
millimeter to which a standard loaded needle will penetrate vertically in 5 seconds
The penetrometer consists of a needle assembly with a total weight of 100g and a device
for releasing and locking in any position
The bitumen is softened to a pouring consistency, stirred thoroughly and poured into
containers at a depth at least 15 mm in excess of the expected penetration.
The test should be conducted at a specified temperature of 25 °C
It may be noted that penetration value is largely influenced by any inaccuracy with regards
to size of the needle, weight placed on the needle and the test temperature
A grade of 40/50 bitumen means the penetration value is in the range 40 to 50 at standard
test conditions
In hot climates, a lower penetration grade is preferred.
Grading of the Bitumen on the basis of test
Results
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Applications and Uses of Aggregates
Aggregates are the most mined material in the world. Construction aggregate is a broad
category of granular raw material of different sizes (sand, gravel, crushed stone, slag,
recycled concrete etc) used in construction.
Also See: Types of Aggregates
Uses of Aggregate
Aggregate can be used in a number of ways in construction. In roads and railway ballast
the aggregates are used to resist the overall (static as well as dynamic) load, to distribute
the load properly to the supporting ground and to drain the water off the surface. In
concrete the aggregate is used for economy, reduce shrinkage and cracks and to
strengthen the structure. They are also used in water filtration and sewage treatment
processes. The uses of aggregates can be summarized in to the following three categories:
As a Load Bearing Material
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As a Filling Material
As an Infiltrating Material
Uses of Aggregate in Concrete
Aggregate is an essential ingredient of concrete. The purpose of aggregates in concrete is:
To provide a rigid structure
To reduce the shrinkage and cracking
Concrete aggregate is used in many structures and substructures e.g. different elements of
a Building, bridges, foundations
The smaller the aggregate size the greater its surface area and the more binding material
(cement) will be required, resulting in a higher cost
The greater the aggregate size the larger will be the voids, resulting in wastage of binding
material(cement)
Hence a mixture of coarse and fine aggregate is used in concrete to avoid both these
problems.
Uses of Aggregate in Railway Ballast
Properties of aggregate used in railway ballast are very different from those used in roads.
A fully loaded train weighs in thousands of tons. To avoid damage to the rails, ground and
other nearby structures a very tough aggregate is needed not only to support this high
weight but also to distribute and transfer it properly to the ground.
Railway ballast generally consists of a tough igneous rock (crushed), such as granite, with
a larger diameter varying between 30mm to 50mm. Particles finer than this diameter in
higher proportion will reduce its drainage properties. While a higher proportion of larger
particles result in the load on the ties being distributed improperly.
Since the angular stones interlock with each other, therefore, they are used to resist any
movement of the rails and ties.
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Determine the Softening Point of Bitumen
(AASHTO DESIGNATION: T-53)
(RING AND BALL APPARATUS)
APPARATUS:
Ring
Ball
Beaker
Ring hold and Assembly
Thermometer
Release Agent
Distilled Water
PROCEDURE:
Heat the bitumen sample with care and stirred to prevent local over heating until it becomes
sufficiently fluid to pour.
Heat the brass ring to approximate pouring temperature, and using one of the release
agents.
Pour the heated bitumen into ring and allow it to cool.
When specimen has cooled cut away excess bitumen clearly with slightly heated knife so
that the top is leveled.
Take distilled water for softening point of different temperature.
Assemble the apparatus.
The ring should be 1 inch above the base of the beaker.
Start heating the beaker from below.
Record the temperature at the instant the ball surrounded by bitumen touches bottom of the
beaker.
32. 32 | P a g e
The temperature thus recorded will be the softening point of the bitumen.
USES AND SIGNIFICANCE:
Bitumen is viscous elastic material without sharply defined melting points. They gradually
become softer and less viscous as the temperature rises. This is the reason why the softening
point of bitumen is determined. Softening point is not a melting point, bituminous material
do not melt but instead gradually change from semi solids to liquids on application to
heating. Softening point is indicative of the tendency of the material to flow at elevated
temperature encountered in service.
To Perform Ductility Test on Bitumen
Ductility test is conducted to determine the amount bitumen will stretch at temperature
below its softening point. A briquette having a cross sectional area of 1 in2
is placed in a
tester at 77 °F. Ductility values ranges from 0 to over 150 depending on the type of
bitumen.
APPARATUS:
Penetration Apparatus
Needle
Container
Water Bath
Thermometer for Water Bath
Stop Watch
PROCEDURE:
33. 33 | P a g e
Ductility is the property of bitumen that permits it to undergo great deformation or
elongation. Ductility is defined as the distance
in cm, to which a standard sample or briquette
of the material will be elongated without
breaking. Dimension of the briquette thus
formed is exactly 1 cm square. The bitumen
sample is heated and poured in the molds
assembly placed on a plate. These samples
with molds are cooled in the air and then in
water bath at 27 °C temperature. The excess
bitumen is cut and the surface is leveled using a hot knife. Then the mould with assembly
containing sample is kept in water bath of the ductility machine for about 90 minutes.
The sides of the moulds are removed, the clips are hooked on the machine and the
machine is operated. The distance up to the point of breaking of thread is the ductility
value which is reported in cm. The ductility value gets affected by factors such as pouring
temperature, test temperature, rate of pulling etc. A minimum ductility value of 75 cm
has been specified by the BIS. shows ductility moulds to be filled with bitumen.
34. 34 | P a g e
Factors Affecting Strength, Hardness and Toughness
of Stones
a. Hardness or softness of the components
b. Proportions of the hard and soft minerals
c. Size and shape of the minerals
d. Cohesion
e. Porosity
f. Density
g. Cementing material
35. 35 | P a g e
a) Hardness or softness of the components:
The composition of the compounds determines its hardness or softness. Stones containing
Si, Na, K are poor while that containing Mg, Ca, and Fe are good, as they are harder. If the
stone is composed of soft and unhardened materials it will result in a soft materials and
vice versa.
b) Proportion of hard and soft materials:
The amount of soft and hard material in a specific sample of stone also matters. Greater
the amount of hard materials more will be the resistance to weathering.
c) Size and shape of the minerals in stones:
Crystalline solids are hard and compact, thus superior to non-crystalline. Finer the crystals,
stronger the stones and vice versa, This property i.e fineness reduces the pores in the stone.
d) Cohesion:
It is the property of atoms or particles to attract each other. The fine grains have more
cohesive power than the coarser grains. Greater the cohesion in stone causes increase in
the hardness, strength and toughness of stones. The property of compactness also depends
deeply on cohesion.
e) Porosity:
Stones in wet conditions and having pores in them allow a lower crushing strength than
normal. Porosity can reduce the strength upto 30 - 40% e.g limestone and sandstone are
affected by this property. Porosity is the property of a substance in which it contains pores
i it. It also reduces the resistance to a concentrated (point) load.
f) Density:
If a stone is compact, dense, it would also be non-porous and strong , thus toughness also
depends upon density.
g) Cementing material:
Stones with silicates as cementing material will be resistant to weathering than those with
calcareous or ferruginous binding material. So, cementing material also affects the choice
of stone selection.
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Selection of Stones for Building Construction
Good Construction Stone Selection
Being cheap, hard, durable and naturally good looking, stones are often used in
construction but keeping in view the variable properties of stones of different types, there
must be some criteria for the selection of stones for construction. The criteria is based upon
the following parameters:
1. Chemical composition of stone:
2. Strength and hardness:
3. Durability:
4. Resistance to fire:
37. 37 | P a g e
5. Bio-Deterioration:
6. Appearance:
7. Susceptibility to being quarried in large sizes:
1. Chemical composition of stones:
Using/selecting a stone for construction, its chemical properties and composition must be
tested and verified because different elements and compounds in stones have different
properties. For instance, Magnesium in Limestone causes it to be more stronger and is
called Dolomite. Feldspar, in large quantities in stone is a source of weakness because
CO2 dissolves Potassium, Sodium, and even Calcium in the Feldspar leaving pure white
clay behind.
Presence of Mica, even less than 2-3% makes stone unsuitable for building purposes.
Stones with silicates as cementing materials are resistant to weathering.
2. Strength and hardness:
The more compact grained and heavier a stone, the more stronger it is. A crystalline stone
is superior to a non-crystalline texture. The specific gravity of good stone should be above
2.7.
Stones used for road metal, paving blocks, floor slabs and railway ballast have to withstand
mainly abrasion or wear and tear. Stone wall subjected to vibrations of machinery and
moving loads should necessarily possess toughness. Strength and hardness itself depend
on some factors:
3) Resistance to heat:
Resistence to heat means that the stone must have a very low amount of expansion due to
large increase in temperature. Silicious materials are good at areas where resistance to fire
is required.
4) Bio-deterioration:
Certain trees and creepers thrust their roots in the joints of stones and have both mechanical
and chemical adverse effects. Special microbes can grow on the surface and in minute
fissures, their by-products cause flaking and discoloration.
5) Appearance:
The aesthetic aspect that is color, appearance and show of stones must also be considered
when being used in a project. Appearance depends on the color and the ease with which
the stone can be dressed, rubbed or polished.
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Specification, Uses and Applications of Geo-Textiles
Specification of Geo-Textiles
Because of the wide variety of geosynthetics available, along with their different polymers,
filaments, bonding mechanisms, thicknesses, masses, and so on, they have a wide range of
physical and mechanical properties. A further complicating factor is the variability of some
properties, even within the same manufactured lot or roll. Differences may sometimes be
due to the test procedures themselves.
Many of our current geosynthetic tests were developed by the textile and polymer
industries, often for quality control of the manufacturing process. Consequently the test
39. 39 | P a g e
values from these tests may not relate well to the civil engineering conditions of a particular
application. Furthermore, soil confinement or interaction is not accounted for in most
geosynthetics testing. Research is now underway to provide test procedures and soil–
geosynthetic interaction properties which are more appropriate for design.
Uses of Geotextiles
1. Separation and Stabilization:
1. A separation layer will stop smaller particles mixing with bigger particles reducing erosion
and increasing bearing capacity of weak soils.
use of geotextile can prove economical as it can reduce the amount of material required for
sub base and increase the life time of the road.
2. Commonly used for separation of Aggregate-base and sub grade layers of roads.
3. Geo-textile prevents the sub grade materials from migrating into the Aggregate base due
to loads thus increasing pavement life
2. Filtration:
To retain the particles of the filtered soil, while permitting water to pass through the plane
of the geo-textile
Rip rap material may be placed over geo-textile along a stream bank
3. Reinforcement:
Geo-textile material under the road-bed reinforces soft soil and preserves the road
embankment. For weak soils it can increase bearing capacity.
4. Transmission:
Some composite geo-textile materials allow water flow within the plane of the material,
rather than across it such as behind a retaining wall. This function is called transmission.
5. Erosion Control:
Permanent erosion control applications:
1. Slope protection,
2. diversion ditches
3. stream and canal banks
4. scour protection
5. beaches, and
6. culvert outlets.
Geocomposites is the use of prefabricated vertical (“wick”) drains to accelerate the
consolidation of soft compressible cohesive soil layers. Because they are much less
expensive to install, geocomposite drains have made conventional sand drains obsolete.
40. 40 | P a g e
Applications of Geo Textiles in Road
Construction:
Geotextiles help prevent the erosion of soil but allows the water to drain off. The biggest
enemy of road structure is water because presence of excess water makes undesirable
changes to the property of road materials, property known as consistency. The layer of
materials like sub-grade, sub-base, base course change their property and thus change the
load bearing capacity, so it is necessary to drain off the water but still we want to hold the
soil together cause we don’t want our road to erode when there is heavy rainfall. In the
interaction between the retention walls and the fill/cut side of road we use geotextiles.
In early days, usually in earthen road even when there was slight rainfall the road used to
get muddy and changed its shape and width so it is necessary that we use geotextiles to
prevent this from happening.
Sources and Types of Pozzolanic Material
Definition
A simple everyday definition of 'pozzolan' could be 'a finely powdered material which
can be added to lime mortar (or to Portland cement mortar) to increase durability. A more
formal definition is given by ASTM C618-84 as 'a siliceous or siliceous and aluminous
41. 41 | P a g e
material which, in itself, possesses little or no cementitious value but which will, in finely
divided form in the presence of moisture, react chemically with calcium hydroxide at
ordinary temperature to form compounds possessing cementitious properties'
Sources and Types of Pozzolanic Material
Pozzolanic materials can be divided into the categories listed below, according to their
origin and properties.
Natural, Very Finely Divided, Highly Reactive Materials of Volcanic Origin:
These materials are formed from a combination of minerals, (mainly consisting of silica
and alumina with smaller and variable quantities of other minerals containing calcium,
magnesium, iron, potassium, and sodium), ejected from volcanoes in the form of very
finely divided vitreous material. Other vitreous volcanic material, such as basalt, may
have mild pozzolanic properties if very finely ground.
These natural pozzolans were widely used in 19th century engineering works in
conjunction with natural hydraulic limes. They were recognized as being particularly
appropriate for marine engineering and other works in difficult wet conditions, and for
civil engineering works generally. Well known sources include puozzolana from
Puozzoli in Italy, volvic pozzolan from South-east France, trass from the Rhineland and
tuff from the Aegean islands. Crushed pumice was also used.
Low Temperature Calcined Clay Products In Various Forms
Pozzolanic additives derived from lightly fired and finely crushed clay products, such as
clay tile or brick, were used by the Romans and combinations of non-hydraulic lime and
low temperature brick dusts have been used over a long period of time. Similar
specifications are successfully employed in modern conservation practice where
additional set and durability are required without seriously reducing the permeability and
flexibility of the mortar.
Bodies such as English Heritage have promoted the use, particularly for conservation
work, of low temperature clay pozzolans in non-hydraulic mortars. Current advice is that
the material should be derived from clay fired at temperatures below 950 °C, and ground
to a range of particle sizes between 38 and 600 microns.Modern sources of potentially
suitable material include reject bricks and tiles from traditional producers, which can be
crushed in a roller pan mill. Some manufacturers also produce low temperature purpose-
made dusts for sale as pozzolans.
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Clay or Kaolin Products Specifically Manufactured as Pozzolans
These are produced primarily for use with Portland cement and all currently available
technical and performance data relates to their use in that context. These materials are
highly reactive and combine readily with calcium hydroxide to form calcium silicate
hydrates and calcium alumino-silicate hydrates. Their effect on the performance and
characteristics of lime mortars is not currently known but, subject to adequate
investigation and trials, it is possible that their use could be extended into this field.
Also falling into the category of fired clays is the material known as HTI (high
temperature insulation) powder. This was widely specified in the 1980s but has now
largely been superseded by lower temperature materials which are thought to be more
consistent in their performance.
Mineral Slag:
Furnace slag is a vitrified material, produced as a by-product of processes such as
smelting, and requires grinding to convert it to a reactive material. It contains silica,
alumina, lime and other minerals in various proportions and, in modern practice, is more
commonly used as an additive in Portland cement concretes. Historically, forge scale and
iron-rich slag, known as minion, were also used.
Ashes of Organic Origin:
Coal cinders generally have an acceptable balance of silica and alumina, and have been
used historically as a pozzolanic additive, but their physical structure tends to weaken the
mortar and to absorb excessive water. Coal ash is widely used, in the form of PFA
(pulverised fuel ash) as an additive to cementitious mortars and in lime-based grouts. The
use of coal-based products carries a risk of sulphate contamination and the materials
should always be selected from low sulphate coals. The residue of fuels from lime
burning, whether from coal-, coke-, or wood-fired kilns, known as lime-ash, is well
known historically as a pozzolan and is still available. Other vegetable ashes, such as rice
husk ash, are used as pozzolans in other parts of the world. Bone ash is also known to
have been used.
Certain Natural Sands and Crushed Rock Products:
Certain types of sand, such as argillaceous (clayey) sands containing high proportions of
schist, basalt, feldspar and mica, can have mildly pozzolanic properties. Whilst these
sands are not generally specified for modern lime-based mortars it may be useful to
recognize that, historically, in certain localities, their use could have influenced the nature
of local lime mortars. Finely crushed rock products from sources containing an
appropriate balance of minerals may also produce a mild pozzolanic effect. Traditionally,
43. 43 | P a g e
mortars were often produced using techniques which brought the sand into contact with
hot slaking lime, and it is possible that this heat would have encouraged any potential for
a mild pozzolanic reaction between sand and lime.
Soil Cement - Definition, Use in Earthfill Dams &
Embankments
In recent years soil cement as a facing material for earthfill dams has been found
economical where suitable riprap is not available near the site. A reasonably firm
foundation is preferred so that deformation after placement of soil-cement is not
significant; however, no unusual design features need be incorporated into the
embankment.
Normal embankment construction procedures are used, with perhaps special care being
taken to ensure a minimum of embankment consolidation and foundation settlement after
construction. The soil-cement is generally placed and compacted in stair-step horizontal
layers. This promotes maximum construction efficiency and operational effectiveness.
With typical embankment slopes of 2:1 and 4:1, a horizontal layer 8 feet wide will provide
minimum protective thicknesses of about 2 and 3l/2 feet respectively, measured normal to
the slope. Beginning at the lowest layer of soil-cement, each succeeding layer is stepped
back a distance equal to the product of the compacted layer thickness in feet times the
embankment slope.
For example, if the compacted thickness is 6 inches and the slope is 2:1, the step back is =
0.5(2) = 1 foot. The usual compacted layer thickness is 6 inches. Soil-cement layers of this
dimension can be effectively placed and compacted with standard highway equipment.
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A plating method that forms a single soil-cement layer parallel to the slope is sometimes
used in less critical areas for slope protection. If the soil-cement facing does not begin at
natural ground level, the lower portion of the embankment should be on a flatter slope than
the portion protected by the soil-cement; or a berm may be provided at the lowest elevation
of the facing. It is essential that the soil-cement extend below the minimum water level and
above the maximum water level. The top of the facing should have a freeboard allowance
of at least 1.2 times the anticipated maximum wave height, or 5 feet, whichever is greater.
The edges of the completed soil-cement layers should not be trimmed because the rounded
starstep effect helps retard wave runup (fig. 6-53). Soil-cement can be made with a wide
variety of soils. The principal criterion for determining soil type is gradation. Coarse sandy
or gravelly soils containing about 10 to 25 percent material passing the No.200 sieve are
ideal (American Society for Testing and Materials Standard Sieve Series). These soils can
be adequately stabilized with from 3 to 5 sacks of cement per cubic yard of compacted soil
cement.
Standard compaction and placement control for soil-cement is used. If the amount of
material smaller than the No.200 sieve exceeds 35 percent, some effort to find a coarse
material may be justified from a processing cost standpoint. Soils containing 50 percent or
more material passing the No.200 sieve are not recommended for use in their natural state.
Any type of Portland cement meeting the requirements of the latest ASTM (American
Society for Testing and Materials), AASHTO (American Association of State Highway
and Transportation Officials), or Federal specifications may be used. Type 1, or normal
Portland cement, is most commonly used because the special properties of other types of
45. 45 | P a g e
Portland cement are not usually required for soil-cement construction. Standard laboratory
tests are necessary to verify the acceptability of the soil and to determine proper cement
content, optimum moisture content, and maximum dry unit weight of the soil-cement. After
the soil has been classified by sieve analyses and other tests, the required cement content
may be estimated. Moisture unit weight curves are determined for test mixtures. The
estimated cement content and at least four moisture contents are used to determine the
optimum moisture content and maximum dry unit weight of the mixture accurately. A
number of test cylinders are prepared, using the estimated cement content and cement
contents 2 percentage points above and below the estimated content.
The results of wet-dry, freeze-thaw, weight-loss criteria will determine the cement content
required. This cement content is then increased by 2 percentage points for erosion
resistance. If it is necessary to use a soil containing more than 50 percent fines, the cement
content should be increased by 4 percentage points for erosion erosion resistance. For most
soils, a total required cement content of 10 to 12 percent by compacted volume of soil-
cement is considered typical. Compressive strength tests for soil-cement are considered
supplementary to the standard soil cement tests. Soil-cement mixtures with a compressive
strength of about 450 lb/in2
or more at 7 days will generally pass the wet-dry and freeze-
thaw tests. Using cement contents of about 10 percent, 7-day compressive strengths of 500
to 1,000 lb/in2
are common with a wide range of soils.
Types of Paints
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Paints can be classified into different types on the basis of:
Their Function
Binder or Medium
Pigment Used
Sheen
Appearance
Based on Their Function
a. Primers or Undercoats
A preparatory coating applied before painting for better adhesion
b. Finishing Coats
Polish to create a smooth and shiny surface
c. Sanding Sealer
Sanding sealer fills small pits and pores. It is usually applied on wooden surfaces to
achieve smother surface
d. Floor Paint
Long lasting paints used to provide good and hard surface finish for concrete or other
rough floors, e.g. Urethane Oil-Based Paint
e. Galvanized Iron Primer
It is a water-based anti-corrosive quick drying coat applied on metal surfaces
f. Spray Paint
Applied with spray gun for even and smooth surface finish
Based on Pigment Used
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a. Zinc Rich or Zinc Dust Primer
Zinc rich paints are used to withstand continuous temperature up to 550 C°
. It is also used
to protect the surface against weathering and corrosion as well as prevention of underfilm
corrosion attack
b. White Lead Paints
It is the cheapest and decolorizes on exposure and is therefore commonly used for ordinary
buildings. It is not suitable for exterior works. It cannot be used as a protection against
corrosion
c. Graphite Paint
It consists of powdered graphite and oil and is used to coat metallic structures
d. Red Lead Paints:
In combination with linseed oil it may be used as a thick, long-lasting anti-corrosive layer
e. Micaceous Iron Oxide
Used for the protection of steel against corrosion
f. Calcium Plumbate Primer:
Can be applied both on timber and metal, and is therefore ideal where the two are
combined. e.g. A metal window frame with a wooden outer frame.
g. Zinc Chromate:
Used as a corrosion resistant agent and increase the durability of the surface several times
Based on Sheen of a Paint
The sheen of paint is the amount of light reflected by the painted surface. Depending on
level of sheen paints may be of four types;
1. Flat Paints
2. Paints with Satin Finish
3. Semi-Gloss Paints
4. Gloss Paints
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Based on Appearance
Eggshell
Multicolored
Matt
Iridescent Texture
Satin Finish
Wrinkle Finish
Semi-Gloss
Luminous
Fluorescent
Gloss
Crackle Finish
Flat
Based on Binder/Medium
Acrylic
Latex Paint
Latex Polyvinyl Acetate (PVA)
Shellac Based Paint
Spirit Based Paint
Epoxy Paint
Polyurethane
Alkyd Resin
Tung Oil Paint
Linseed Oil Paint
Distemper
Emulsion
Chlorinated Rubber
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Preparation and Applications of Paints
Composition of Paints
Base/ body is thoroughly grounded in the vehicle
Mixed with the thinner to impart necessary workability
Pigments and dryers are separately mixed to a thin consistency
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The two are then thoroughly mixed to form the desired paint
Applications of Paints
Paint can be applied as a solid, a gaseous suspension (aerosol) or a liquid. Techniques
vary depending on the practical or artistic results desired.
As a solid (usually used in industrial and automotive applications), the paint is applied as
a very fine powder, then baked at high temperature. This melts the powder and causes it
to adhere (stick) to the surface. The reasons for doing this involve the chemistries of the
paint, the surface itself, and perhaps even the chemistry of the substrate (the overall
object being painted).
As a gas or as a gaseous suspension, the paint is suspended in solid or liquid form in a gas
that is sprayed on an object. The paint sticks to the object. The reasons for doing this
include:
the application mechanism is air and thus no solid object ever touches the object being
painted;
the distribution of the paint is very uniform so there are no sharp lines
it is possible to deliver very small amounts of paint or to paint very slowly;
a chemical (typically a solvent) can be sprayed along with the paint to dissolve together
both the delivered paint and the chemicals on the surface of the object being painted;
some chemical reactions in paint involve the orientation of the paint molecules.
In the liquid application, paint can be applied by direct application using brushes, paint
rollers, blades, other instruments, or body parts. Examples of body parts include finger-
painting, where the paint is applied by hand, whole-body painting (popular in the 1960s
avant-garde movement), and cave painting, in which a pigment (usually finely-ground
charcoal) is held in the mouth and spat at a wall.
Rollers generally have a handle that allows for different lengths of poles which can be
attached to allow for painting at different heights. Generally, roller application takes two
coats for even color. A roller with a thicker nap is used to apply paint on uneven surfaces.
Edges are often finished with an angled brush.
After liquid paint is applied, there is an interval during which it can be blended with
additional painted regions (at the "wet edge") called "open time." The open time of an oil
or alkyd-based emulsion paint can be extended by adding white spirit, similar glycols
such as Dowanol™ (propylene glycol ether) or commercial open time prolongers. This
can also facilitate the mixing of different wet paint layers for aesthetic effect. Latex and
acrylic emulsions require the use of drying retardants suitable for water-based coatings.
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Paint may also be applied by flipping the paint, dripping, or by dipping an object in paint.
Interior/exterior house paint tends to separate when stored, the heavier components
settling to the bottom. It should be mixed before use, with a flat wooden stick or a paint
mixing accessory; pouring it back and forth between two containers is also an effective
manual mixing method. Paint stores have machines for mixing the paint by shaking it
vigorously in the can for a few minutes.
Water-based paints tend to be the safest, and easiest to clean up after using -- the brushes
and rollers can be cleaned with soap and water.It is difficult to reseal the paint container
and store the paint well for a long period of time. Store upside down, for a good seal, in a
cool dry place. Protect from freezing.
Proper disposal of paint is a challenge. Avoid acquiring excess paint. Look for suitable
recycled paint before buying more. Try to find recycled uses for your left over paint.
Paints of similar chemistry can be mixed to make a larger amount of a uniform color. Old
paint may be usable for a primer coat or an intermediate coat. If you must dispose of
paint, small quantities of water based paint can be carefully dried by leaving the lid off
until it solidifies, and then disposing with normal trash. But oil based paint should be
treated as hazardous waste, and disposed of according to local regulation.
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Properties & Tests on Paints
Properties of Paints
Tests on Paints
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1. Important buildings were once designed and put together by master masons who
knew how to work with stone, and understood the advantages and limitations of the
material. Stone structure should be a combination of structural firmness, technical
commodity and aesthetic delight.
2. Ensure proper wall construction. The wall thickness should not exceed 450mm.
3. Round stone boulders should not be used in the construction! Instead, the stones
should be shaped using chisels and hammers.
4. Use of mud mortar should be avoided in higher seismic zones. Instead, cement-sand
mortar should be 1:6 (or richer) and lime-sand mortar 1:3 (or richer) should be used.
5. Ensure proper bond in masonry courses: The masonry walls should be built in
construction lifts not exceeding 600mm.
6. Through-stones (each extending over full thickness of wall) or a pair of overlapping
bond-stones (each extending over at least ¾ ths thickness of wall) must be used at
every 600mm along the height and at a maximum spacing of 1.2m along the length.
7. The stone masonry dwellings must have horizontal bands roof and gable bands).
These bands can be constructed out of wood or reinforced concrete, and chosen
based on economy. It is important to provide at least one band (either lintel band or
roof band) in stone masonry construction.
8. Care should be taken to ensure that the fixing method adopted for the construction
is appropriate to the type of stone being used.
The energy needed to collapse a structure comes from the structure itself. The high
frequencies can cause high vertical inter-stone vibrations that result in irreversible relative
displacements of the stones, which is mainly due to the non required shape of the stones,
thus stone walls mainly crumble under their own weight.
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How and When to Paint and its Purpose
Painting Order and Steps
1. Ceiling
Paint away from light sources such as windows.
2. Walls
Cut in to the ceiling with a clean line. Then start in high corner, and work across and
down in 1 metre square sections.
3. Windows
Mask glass if preferred. Paint window sash before frame.
55. 55 | P a g e
4. Doors and architraves
Paint frame before door.
5. Skirting
Use a small brush and piece of cardboard or a wallpapering straight edge to keep paint off
the carpet.
1. Cabinets and shelves
In this order: Back wall, side walls, shelf tops and edges, shelf bottoms, inside doors,
outside doors, outside cabinet and drawer fronts. The tools required will largely
depend upon the condition and type of the surface being painted. Most common
tools and equipment used are as below:
1. Sandpaper
2. Scraper
3. Hot air gun
4. Bucket
5. Rubber gloves
6. Flat filling and stripping scrapers
7. Brushes -75mm is as large as you need inside
8. Roller, tray and appropriate sleeves
9. Paint pads and tray
10. Drop sheets
11. Masking tape
12. Step ladder
13. Trestles and planks
How to paint?
Before painting, wood siding and trim should be treated with a paintable water-repellent
preservative or simple water repellent. This can be done by brush after the siding or trim is
up, or by dipping before it’s installed. If you work by brush, all lap and butt joints in solid
wood or all panel edges should be especially well saturated. Allow at least two warm, sunny
days for adequate drying of the treatment before applying the primer paint coat. If the
wood’s been dip-treated, you should let it dry even longer—about a week. Woods like red
wood and cedar have water-soluble extractives that can bleed through top coats fairly
easily. The best way to prevent this is to seal the wood well with an oil- base primer or a
stain locking acrylic primer paint. When applying the primer, follow the application
instructions provided by the manufacturer. A primer coat that is uniform in thickness will
distribute the wood’s swelling stresses evenly, which helps to prevent premature paint
failure.
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Research has shown that the optimum thickness for the total dry paint coat (primer and two
top coats) is 3.5 to 5 mils, or about the thickness of a sheet of newspaper. TWO coats of a
good-quality acrylic latex house paint should be applied over the primer. In general, qualify
is directly related to price. Brush application is always superior to roller or spray
application, especially with the first top coat. If it isn’t practical to apply two top coats
everywhere, just do it where they will be needed most—on the south and west sides of the
house where the most sunlight will hit.
Areas exposed to rain wetting should also get two coats
To avoid future Separation between paint coats, the first top coat should be applied within
two weeks of the prime coat, and the second top coat should be applied within two weeks
of the first. Otherwise, the slick, soap like substance that can form on a recently painted
surface will inhibit paint adhesion (this is especially true with primer paints). If this film is
detectable, it should be scrubbed off with water and a stiff-bristled brush before you recoat.
If you’re using oil-base top coats, don’t paint on a cool surface that will be heated by the
sun within a few hours. This will probably cause temperature blistering. The blisters
usually show up in the topmost coat anywhere from a few hours to a few days after the
paint is applied. Oil-base paint may be applied at temperatures above 40°F, while latex or
water-base paints re- quire application temperatures of at least 50°F. The temperature
shouldn’t drop below 50°F for at least 24 hours after a latex coat is applied.
To avoid wrinkling, fading or loss of gloss, don’t apply paint at the end of a
cool day
When heavy dew will form at night. Some latex paints are particularly susceptible to failure
when applied under these conditions. Semi-transparent penetrating stains may be brushed,
sprayed or rolled on. Again, brushing will give the best results. These stains tend to be thin,
so application can be messy. And the pigment may settle in an undisturbed can, so frequent
mixing is important. To prevent lap marks, always avoid stopping in the middle of a board
or panel. Working in the shade will give the best results because longer drying time means
greater penetration. For best results, rough sawn or weathered lumber should be treated
with two coats of penetrating stain, with the second one applied before the first is dry.
In fact, if the first coat has dried completely, it may seal the wood surface temporarily so
that the second coat hardly penetrates at all. About an hour after applying the second coat,
use a cloth, sponge or dry brush Iightly wetted with stain to wipe off any excess stain that
hasn’t penetrated into the wood. This prevents surface deposits from drying into filmy
spots. Remember that sponges or cloths soaked with oil-base or alkyd.base stains are
particularly susceptible to spontaneous combustion; they should be buried, immersed In
water or sealed in an airtight container.
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When to paint? Why to Paint?
1. To avoid cracks, fissures and air spaces.
2. To avoid weathering
3. To beautify the appearance and have durability
4. Ensure proper bond in masonry courses: The masonry walls should be built in
construction lifts not exceeding 600mm.
5. Painting protects wood from Ultra-Voilet degradation and simple erosion
6. It seals into the wood the natural resins and oils
7. Retards penetration of exterior moisture into the wood surface and prevents its
swelling
8. The primary function of any wood finish (paint, varnish, wax, stain, oil, etc.) is to
protect the wood surface, help maintain appearance, and provide cleanability.
9. Wood surfaces exposed to the weather without any finish change color, are
roughened by photo-degradation and surface checking, and erode slowly. Wood
surfaces exposed indoors may change color and accumulate dirt and grease if left
unprotected without some finish.
10.Wood and wood-based products in a variety of species, grain patterns, textures, and
colors can be finished effectively by many different methods
Paint, however, is not a preservative; it will not prevent decay if conditions are favorable
for fungal growth.
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Properties of Wood & Timber - Physical and Chemical
Properties of Wood
Wood is the oldest material used by humans for construction after stone. Despite its
complex chemical nature, wood has excellent properties which lend themselves to human
use. It is readily and economically available; easily machinable; amenable to fabrication
into an infinite variety of sizes and shapes using simple on-site building techniques;
Exceptionally strong relative to its weight
A good heat and electrical insulator;
of increasing importance
It is a renewable and biodegradable resource.
However, it also has some drawbacks of which the user must be aware. It is a “natural”
material and is available in limited amount.
Physical Properties | | Chemical Properties
Physical properties of Timber:
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Following properties of
wood makes it good for use in
construction.
Specific Gravity (SG):
Generally, specific gravity (SG) and the major strength properties of wood are directly
related. SG for the major, usually used structural species ranges from roughly 0.30 to
0.90. Higher allowable design values are assigned to those pieces having narrower
growth rings (more rings per inch) or more dense latewood per growth ring and, hence,
higher SG.
Moisture Content (MC) and Shrinkage:
Undoubtedly, wood’s reaction to moisture provides more problems than any other factor
in its use. Wood is hygroscopic ; that is, it picks up or gives off moisture to equalize with
the relative humidity and temperature in the atmosphere. As it does so, it changes in
strength; bending strength can increase by about 50% in going from green to a moisture
content (MC) found in wood members in a residential structure, for example. Wood also
shrinks as it dries, or swells as it picks up moisture, with concomitant warpage potential.
Critical in this process is the fiber saturation point (fsp) , the point (about 25% moisture
content, on oven-dry basis) below which the hollow center of the cell has lost its fluid
contents, the cell walls begin to dry and shrink, and wood strength begins to increase. The
swelling and shrinkage processes are reversible and approximately linear between fiber
saturation point and 0% MC.
Wood decay or fungal stain do not occur when the MC is below 20%. There is no
practical way to prevent moisture change in wood; most wood finishes and coatings only
slow the process down. Thus, vapor barriers, adequate ventilation, exclusion of water
from wood, or preservative treatment are absolutely essential in wood construction.
Thermal Properties/Temperature Effects:
Although wood is an excellent heat insulator, its strength and other properties are affected
adversely by exposure for extended periods to temperatures above about 100°F. The
combination of high relative humidity or MC and high temperatures, as in un-ventilated
attic areas, can have serious effects on roof sheathing materials and structural elements
over and above the potential for attack by decay organisms. Simple remedies and caution
usually prevent any problems.
At temperatures above 220°F, wood takes on a thermoplastic behavior. This characteristic,
which is rarely encountered in normal construction, is an advantage in the manufacture of
some reconstituted board products, where high temperatures and pressures are utilized.
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Environmentally friendly
Timber is the most environmentally responsible building material. Timber has low
production energy requirements and is a net carbon absorber. Timber is a renewable
resource. Well-managed forests produce timber on a sustained continuous basis, with
minimal adverse effects on soil and water values.
In plentiful and growing supply
Timber is readily available. Australia has significant forest resources including a
plantation estate covering more than 1.6 million hectares, and the area is growing rapidly.
Strong and lightweight
Timber is strong, light and reliable making timber construction simpler and safer than steel
or concrete construction. A comparison with steel and concrete shows that radiata pine
structural timber, for example, has a strength for weight ratio 20 percent higher than
structural steel and four to five times better than un-reinforced concrete in compression.
The lightweight structures possible in wood confer flow-on advantages in terms of reduced
foundation costs, reduced earthquake loading and easier transport. Building components
and complete constructions are simple and safe to erect, and cheaper to deconstruct or reuse
at the end of a building is useful life.
Additionally, timber must be:
Safe
Timber has low toxicity and therefore requires no special safety precautions to work with
it, other than normal protection from dusts and splinters. Timber frame construction
requires little in the way of heavy lifting equipment making building sites safer work
places. Timber being non-conductive has obvious benefits in terms of electrical safety.
Modern timber construction has increased fire resistance due to incombustible linings
protecting light frames.
Easy to install
Increasingly specialist timber frame and truss manufacturers use high tech prefabrication
enabling accurate and speedy installation. Recyclable - Timber is a forgiving material
that can be easily disassembled and reworked. If demolition or deconstruction of a
wooden building is necessary, many wood-based products can be recycled or reused.
Timber trusses and frames, factory fabricated from sawn timber and toothed metal plate
connectors, have come to dominate roof construction for small buildings such as houses
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and large industrial buildings where clear spans up to 50 metres are required. Timber
trusses compete with other roof structural systems on cost, high performance, versatility
and ready availability, supported by design software packages supplied by the plate
manufacturers to the fabricators.
Cost effective
Comparative studies of the economics of different wall framing systems indicate that, in
terms of direct building expenses, timber frames are consistently the most cost-effective
solution. There are many factors to consider when comparing the economics of different
construction systems including the complexity of the layout, site, builder experience, and
relative material prices at the time of building. However, comparative studies of the
economics of different wall framing systems indicate that, in terms of direct building
expenses, timber frames are consistently the most cost-effective solution.
In the medium to long term, the forecasts for the Australian wood supply indicate a stable
and growing supply. This means that prices for framing timber are likely to be more
stable for builders in the long term. However, this price stability is questionable for
materials such as steel, which consume considerable amounts of fossil fuels in their
manufacture. The smelting of steel is heavily reliant on the continued availability of
cheap sources of fossil fuels, a scenario which is becoming highly uncertain in an
increasingly energy and security conscious world.
Durable
Properties of timber also include durability. Good detailing, coating and maintenance
ensure that timber structures last for lifetimes. Although many buildings become obsolete
and are demolished long before the end of their natural lives, timber buildings correctly
designed and maintained can have an indefinite life. The key to long life is protection
from weather, insect attack and decay, through well-established design detailing, surface
coating systems, selection of durable species, and preservative treatment processes. In all
countries of the world, and Australia is no exception, historic timber buildings testify to
these principles.
In termite-prone areas, all buildings are vulnerable to termite attack of contents, so
protection is needed regardless of construction materials. Protection systems rely on
physical or chemical barriers, or both, and their effectiveness depends on the quality of
the design, construction, inspection and maintenance. The risk of termite attack should be
assessed after consulting with local building authorities and an appropriate termite
management system should be implemented.
The system may include physical or chemical barriers or in higher risk areas, a termite
resistant treated timber or naturally termite resistant frame may also be chosen. In any
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case any management system should include regular inspection to ensure that barriers
have not been breached. It is therefore critical that the system type and inspection
schedule are understood by all future householders. Importantly, termites are an integral
part of the ecology of Australia, however, with awareness, planning and using cost
effective systems, they can be effectively managed.
Comfortable
Well-designed Timber structures are comfortable to live in all year round no matter
where you are.
Flexible
A particular feature of timber is the flexibility of design forms and finishes that can be
used. This flexibility also extends to the ease with which existing buildings can be added
to or modified to suit changing circumstances. User friendly versatile timber gives
building designers creative freedom providing homeowners with flexible design
choices.Timber is simply the best building material for builders, designers and
homeowners and can be used to construct the homes we love, structures we admire and
warehouses, commercial buildings and other structures. The timber frame method of
building gives designers flexibility in both layout and external appearance. High levels of
thermal insulation are incorporated within the construction, reducing heating costs and
conserving energy.
Compression Strength
An important property of timber is that it should have adequate compression strength to
be used for different purposes in construction industry.
Chemical Properties of Timber Wood
Chemical Effects
Though, would is chemically inert as compared to other materials but is affected by some
acids and bases. Some species have proven very useful for food containers (berry boxes
and crates) because they are nontoxic and impart no taste to the foods contained therein.
Wood structures have also found widespread use as storage facilities for salt and fertilizer
chemicals.
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Tests & Properties of Geotextiles
Properties of GeoTextiles
Because of the wide variety of geosynthetics available along with their different polymers,
filaments, bonding mechanisms, thicknesses, masses, and so on, they have a wide range of
physical and mechanical properties.
A further complicating factor is the variability of some properties, even within the same
manufactured lot or roll. Differences may sometimes be due to the test procedures
themselves. Consequently the test values from these tests may not relate well to the civil
engineering conditions of a particular application.
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Furthermore, soil confinement or interaction is not accounted for in most geosynthetics
testing. Research is now underway to provide test procedures and soil–geosynthetic
interaction properties which are more appropriate for design.
What is Plaster of Paris and How to Make it at Home?
Plaster of Paris Recipe
Plaster of Paris is a Calcium sulfate semi-hydrate (CaSO4,½ H2O) derived from Gypsum, a
calcium sulfate di-hydrate (CaSO4, 2H2O), by firing this mineral at relatively low
temperature and thus reducing it to powder.
CaSO4, 2H2O + HEAT -------> CaSO4, 1/2 H2O + 1.5 H2O
In 1700’s, Paris was already the “Capital of plaster” since all the walls of wooden houses
were covered with plaster, as a protection against fire. The King of France enforced rule
after the big fire in England 1666.
Large Gypsum deposits near Paris ► Mined ► Manufacture of Plaster of Paris
Items Needed
(Apparatus) to make plaster of Paris with glue
2 parts Diluted White Glue
1 part Warm Water
Large Mixing Bowl
Spatula or Wooden Spoon
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Instructions and procedure
Gather all the materials and spread a sheet on the work surface.
Now, pour the glue in the large mixing bowl and beat it well.
Make a paste, by adding one part warm water to two parts of white glue.
Mix the ingredients well. Continue stirring them, until there no visible lumps remain.
If you do not get a soupy mixture, you can add more water to the bowl and mix well.
The final product should be watery, but with a slight white glue consistency.
Properties of Plaster of Paris
It is fine hygroscopic white powder
Its melting point is 1630C
Its density is 2.63 g/cm3
It sets quickly on mixing with water giving out heat
Expands slightly on setting
Uses of Plaster of Paris
Because of its property of slight expansion on setting, it is used for filling cracks and holes
in plaster
It is also used for filling cracks and knots in wooden surface before painting polishing
Plaster of Paris is used in making surgical bandages where movable parts of the body are
to be held rigidly in place
It is used in chalk
As plaster of Paris has high melting point, it is used for plastering the walls of wooden
houses, such as a protection against fire
It is used for making models and statues
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Manufacturing and Uses of Portland Cement
Definition of OPC
Cement can be defined as the bonding material having cohesive & adhesive properties
which makes it capable to unite the different construction materials and form the
compacted assembly. Ordinary/Normal Portland cement is one of the most widely used
type of Portland Cement. The name Portland cement was given by Joseph Aspdin in 1824
due to its similarity in colour and its quality when it hardens like Portland stone. Portland
stone is white grey limestone in island of Portland, Dorset.
Production & Manufacturing:
Today, Ordinary Portland cement is the most widely used building material in the world
with about 1.56 billion tones produced each year. Annual global production of Portland
cement concrete is around 3.8 million cubic meters per year. In Pakistan; cement
production will go beyond 45 million tons per year in the next two years
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Manufacturing
Raw Materials
1. Calcareous (material having content of lime)
2. Argillaceous (material having contents of silica & alumina)
3. Gypsum
Process
Cement is usually manufactured by two processes:
1. Wet process
2. Dry process
These two processes differ in operation but fundamentals of both these processes are same.
In Pakistan, most of the factories use Wet Process for the production of cement. There are
five stages in manufacturing of cement by wet process:
1. Crushing and grinding of raw material
2. Mixing the material in proportion
3. Heating the prepared mixture in rotary kiln
4. Grinding the heated product known as clinker
5. Mixing and grinding of cement clinker with gypsum
Crushing and Grinding:
In this phase, soft raw materials are first crushed into suitable size. This is done usually in
cylindrical ball or tube mills containing the charge of steel balls
Mixing the Material:
In this part, the powdered limestone is mixed with the clay paste in proper proportion
(75%=lime stone; clay=25%)
The mixture is then grounded and made homogeneous by mean of compressed gas. The
resulting material is known as slurry having 35-40% water.
Heating the slurry in rotary kiln:
Slurry is then introduced in rotary kiln with help of conveyor. The rotary kiln consists of
large cylinders 8 to 15 feet in diameter & height of 300-500 feet. It is made with steel & is
usually lined inside with firebricks.
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Kiln rotates at the rate of 1-2 revolution per minute. In rotary kiln, slurry is passed through
different zones of temperature. This whole process in kiln usually covers 2 to 3 hours.
Different temperature zones are as under:
Preheating Zone
In this zone, temperature is kept at 500 degree Celsius & usually the moisture is removed
& clay is broken into silica, aluminum oxide, iron oxide.
Decomposition Zone
Temperature is raised up to 800 degree Celsius. In this zone lime stone decomposes into
lime and CO2.
Burning Zone
In this zone temperature is maintained up to 1500 degree Celsius and the oxides formed in
above zones combine together and form respective silicate, aluminates & ferrite.
Cooling Zone
This is last stage where the whole assembly cooled is up to 150 to 200 degree Celsius.
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Clinker Formation
The product which is obtained from the rotary kiln is known as the cement Clinker. Clinker
is usually in the form of greenish black or grey colored balls.
Grinding the Clinker with Gypsum
The Cement Clinker is then air cooled. The required amount of Gypsum (5 %) is ground
to the fine powder, and then mixed with the Clinker. Finally cement is packed in bags and
then transported to the required site.
Setting and Hardening:
When ordinary Portland cement is mixed with water its chemical compound constituents
undergo a series of chemical reactions that cause it to set. These chemical reactions all
involve the addition of water to the basic chemical compounds. This chemical reaction with
water is called "hydration". Each one of these reactions occurs at a different time and with
different rates. Addition of all these reactions gives the knowledge about how Ordinary
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Portland cement hardens and gains strength. Those compounds and their role in hardening
of cement are as under:
1. Tricalcium silicate (C3S): Hydrates and hardens rapidly and is largely responsible for
initial set and early strength. Ordinary Portland cements with higher percentages of C3S
will exhibit higher early strength.
2. Dicalcium silicate (C2S): Hydrates and hardens slowly and is largely responsible for
strength increases beyond one week.
3. Tricalcium aluminate (C3A): Hydrates and hardens the quickest. It liberates a large
amount of heat almost immediately and contributes somewhat to early strength. Gypsum
is added to Ordinary Portland cement to retard C3A hydration. Without gypsum, C3A
hydration would cause ordinary Portland cement to set almost immediately after adding
water.
4. Tetracalcium aluminoferrite (C4AF): Hydrates rapidly but contributes very little to
strength. Most ordinary Portland cement color effects are due to C4AF.
Uses of OPC (Ordinary Portland Cement):
It is used for general construction purposes where special properties are not required. It is
normally used for the reinforced concrete buildings, bridges, pavements, and where soil
conditions are normal. It is also used for most of concrete masonry units and for all uses
where the concrete is not subject to special sulfate hazard or where the heat generated by
the hydration of cement is not objectionable. It has great resistance to cracking and
shrinkage but has less resistance to chemical attacks.
Tests On Ordinary Portland Cement
1. Fineness test
2. Soundness test
3. Setting time test
4. Strength tests
1. Compressive strength test
2. Tensile strength test
3. Flexural strength test
5. Specific gravity test
6. Consistency test
7. Heat of hydration test
8. Loss of ignition test
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Methods of Natural Seasoning of Wood
Artificial methods of Seasoning of Wood
Air Seasoning
The traditional method of seasoning timber was to stack it in air and let the heat of the
atmosphere and the natural air movement around the stacked timber remove the moisture.
The process has undergone a number of refinements over the years that have made it more
efficient and reduced the quantity of wood that was damaged by drying too quickly near
the ends in air seasoning.
Method of Air Seasoning / Natural Seasoning
The basic principle is to stack the timber so that plenty of air can circulate around each
piece. The timber is stacked with wide spaces between each piece horizontally, and with
strips of wood between each layer ensuring that there is a vertical separation too. Air can
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then circulate around and through the stack, to slowly remove moisture. In some cases,
weights can be placed on top of the stacks to prevent warping of the timber as it dries.
Moisture loss from the side of the wood is at about the right rate not to cause collapse of
the cells, but near the ends of the wood, the moisture loss can prove to be too fast. Often
the ends are wrapped or painted to slow the moisture loss from the end grain. While little
additional energy needs to be supplied for this type of seasoning, the stacks of timber
require a lot of land, represent a potential fire hazard, and the product is not able to be sold
for a considerable time. The interest costs on holding stock for long periods can prove
significant.
Air-drying of timber is really a more controlled facilitation of what happens to unseasoned
sawn, timber, once it is placed into its “work” environment. The amount of drying that can
occur is very much governed by the relative humidity of the drying environment and will
often vary within individual boards as well as within the stack itself. The time taken for
air-drying is a function of the thickness of the timber.
Air-drying is necessarily a slow process, particularly for hardwoods, typically taking 6 to
9 months to reach moisture content in the range 20% to 25%.Air seasoning is the method
used with the timber stacked in the open air. It requires the following:
Stacked stable and safely with horizontal spacing of at least 25 mm.
Vertical spacing achieved by using timber battens (piling sticks) of the same or neutral
species. Today some timber yards are using plastics. The piling sticks should be vertically
aligned and spaced close enough to prevent bowing say 600 to 1200 mm max centers.
Ends of boards sealed by using a suitable sealer or cover to prevent too rapid drying out
via the end grain.
The stack raised well clear of the ground, vegetation, etc to provide good air circulation
and free from rising damp, frost, etc.
Over head cover from effects of direct sunlight and driving weather.
The details depend on the size, quantity and species of the timber. You cannot however
expect to obtain less than 16 - 17% mc in the UK. Further seasoning needs to be done
inside, in heated and ventilated buildings. Of the methods available for seasoning wood,
air drying is the oldest and simplest. Air dried lumber is suitable for exterior use, and green
timber is also frequently allowed to partially air dry prior to kiln drying. Since the
effectiveness of the drying process depends upon weather conditions which control the
drying rate and the final moisture content which can be reached, air drying has been
replaced by kiln drying in many areas but is still an important process.
Most air seasoned material is dried in flat piles with stickers placed between layers, but
when it is essential to have rapid drying to prevent sap stain, end piling may be used. In
humid areas this may be necessary if a dry kiln is not available. Such end racking promotes
good air circulation and consequent rapid drying which eliminates the staining problem but
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often causes end surface checking and warping of the material. Another method of piling
once used to promote rapid drying was edge piling.
Although it is generally thought that air drying is a gentle method of seasoning timber, it
is often severe depending on the time of the year and the species involved. Material cut
from the oaks, sycamore, beech, maple, and other woods which have large rays will surface
check readily and consequently thick material cut from these trees is given special
treatment. To eliminate rapid end drying, the ends are frequently coated with a material
such as paraffin or tar to retard evaporation, but often this is not enough protection, and it
is necessary to place the material in what are known as semi-kilns in which the drying rate
is still more retarded.
Semi-kilns are often nothing more than covered sheds in which the material is piled, but
they may often be large enclosed buildings in which low heat and controlled humidity are
used to slow the drying process. In semi-kilns, where the temperature is maintained at 110
°F to 120 °F and fans are used to circulate the air, green stock may be dried to 8 to 12
percent moisture content in 3 months
Piling Lumber for air drying:
The objective of air drying wood is to remove the water in wood by exposing all surfaces
of each piece of wood to circulating air. In Missouri, wood can be air dried to a minimum
of about 15 percent moisture content, provided the drying time is sufficiently long. It is
also necessary to support the wood during drying to prevent the lumber from warping
during the drying process. Lumber is piled in a special way to maximize the surface
exposure of each piece of lumber to the air and at the same time to support each piece so it
will dry straight and without unnecessary warping.
The first consideration is to prepare a strong foundation, 1 to 2 feet above the ground, on
which to pile the lumber. The ground beneath the foundation should be kept free of
vegetation or debris that would hinder air circulation under the pile.
Your lumber probably will be cut in random lengths and widths. For best results, pile each
course so that each board within a layer is well supported and does not protrude at either
end of the pile.
This system of piling is called "box piling" and has proven to be the best method of piling
random length lumber. The outside boards of each tier are full length. This is important to
tie the pile together and make it less subject to tilting or falling over. Leave spaces between
adjacent boards approximately equal to the thickness of the boards.
Plan view of a tier of boards, illustrating the system of alternating short lengths for box
piling. Unsupported ends of boards placed on the inside of the pile will dry with fewer
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defects than if allowed to extend over the end of the pile. An adequate supply of wooden
sticks (spacers) will be needed to separate each layer (Figures 1 and 2). It is very important
that the sticks be uniform in thickness. Sticks usually are cut 3/4-inch thick. Note that the
stickers are carefully aligned vertically (Figure 2) so that each layer of lumber will be
supported from the base of the pile. If the stickers are not properly aligned, forces will be
created in the drying lumber that will result in permanent kinking of the lumber.
Diagram of essential features of good lumber stacking for proper seasoning. Finally, cover
the pile with old boards, plywood, corrugated metal or any materials that will protect the
top layers of lumber from sun and rain. It is also a good idea to weight the top by placing
heavy objects such as concrete blocks or stones on the roof. This will reduce warping in
the top tiers of the pile as well as secure the roof on the pile.
Drying time:
In warm weather (April through October), 1-inch lumber can be dried to 15 or 20 percent
moisture content in 45 to 60 days (2-inch lumber in 60 to 90 days). In the winter months,
lumber will require twice as long to dry. Lumber at 15 percent to 20 percent moisture
content is adequate for building unheated structures such as garages or barns. If the wood
is to be used inside a heated structure, further drying in a commercial kiln is necessary (6
percent to 8 percent moisture content for indoor use.)
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Process of Steel Manufacturing
MANUFACTURE OF STEEL
Three basic raw materials are needed in large quantities for the production
of steel
1. Iron Ore
2. Coal
3. Lime stone
The first step in the steel manufacture begins at the blast furnace. To
separate iron from iron ore ► coke (substance when gas is taken out of
coal), limestone and dolomite are charged into the blast furnace
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Temperature raised to 1600o
F. This high temp causes the coke to burn and
melt the iron. This red hot iron drained at an opening at the base of the
furnace. Natural gas is often injected to reduce the amount of coke
consumed. The dolomite and limestone combine with the non-ferrous
elements of the ore to form a slag, which floats on the top of the molten iron
and is removed separately. The product of the blast furnace is known as “Pig
Iron” the basic ingredient of steel.
It takes 2 tons of iron ore, 2/3 ton of coke, ½ ton of limestone, 4 tons of air to
make 1 ton of Pig iron. Some of the pig iron goes to the foundries to make
iron castings, but the vast majority is re melted and used in the production of
steel in steel furnace. Several types of furnaces are used for the production
of steel including
Open Hearth Furnace
Bessemer Furnace
Electric Furnace
New Oxygen Furnace
Types of Metals used in Civil Engineering