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Файл:Сonstruction equipment for civil engineers. Учебно-практическое пособие
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materials are expensive and lack structural qualities such as tensile
strength or hardness.
Glass
Glassmaking is considered an art form as well as an industrial process
or material.
Clear windows have been used since the invention of glass to cover
small openings in a building. They provided humans with the ability
to both let light into rooms while at the same time keeping inclement
weather outside. Glass is generally made from mixtures of sand and
silicates, in a very hot fire stove called a kiln and is very brittle. Very
often additives are added to the mixture when making to produce glass
with shades of colours or various characteristics (such as bullet proof
glass, or light emittance).
The use of glass in architectural buildings has become very popular
in the modern culture. Glass “curtain walls” can be used to cover the
entire facade of a building, or it can be used to span over a wide roof
structure in a “space frame”. These uses though require some sort of
frame to hold sections of glass together, as glass by itsself is too brittle
and would require an overly large kiln to be used to span such large areas
by itself.
Plastic
The term plastics covers a range of synthetic or semi-synthetic
organic condensation or polymerization products that can be molded
or extruded into objects or films or fibers. Their name is derived from
the fact that in their semi-liquid state they are malleable, or have the
property of plasticity. Plastics vary immensely in heat tolerance,
hardness, and resiliency. Combined with this adaptability, the general
uniformity of composition and lightness of plastics ensures their use in
almost all industrial applications today.
Foam
More recently synthetic polystyrene or polyurethane foam has been
used in combination with structural materials, such as concrete. It is
light weight, easily shaped and an excellent insulator. It is usually used
as part of a structural insulated panel where the foam is sandwiched
between wood or cement or insulated concrete forms where concrete is
sandwiched between two layers of foam.
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Cement composites
Cement bonded composites are made of hydrated cement paste
that binds wood or alike particles or fibers to make pre-cast building
components. Various fiberous materials including paper and fiberglass
have been used as binders.
Wood and natural fibres are composed of various soluble organic
compounds like carbohydrates, glycosides and phenolics. These
compounds are known to retard cement setting. Therefore, before using
a wood in making cement boned composites, its compatibility with
cement is assessed.
Wood-cement compatibility is the ratio of a parameter related to the
property of a wood-cement composite to that of a neat cement paste.
The compatibility is often expressed as a percentage value. To determine
wood-cement compatibility, methods based on different properties
are used, such as, hydration characteristics, strength, interfacial bond
and morphology. Various methods are used by researchers such as the
measurement of hydration characteristics of a cement-aggregate mix; the
comparison of the mechanical properties of cement-aggregate mixes and
the visual assessment of microstructural properties of the wood-cement
mixes. It has been found that the hydration test by measuring the change
in hydration temperature with time is the most convenient method.
Recently, Karade et al. have reviewed these methods of compatibility
assessment and suggested a method based on the “maturity concept” i.e.
taking in consideration both time and temperature of cement hydration
reaction.
Modern Industry
Modern building is a multibillion dollar industry, and the production
and harvesting of raw materials for building purposes is on a world wide
scale. Often being a primary governmental and trade keypoint between
nations. Environmental concerns are also becoming a major world topic
concerning the availability and sustainability of certain materials, and
the extraction of such large quantities needed for the human habitat.
Building Products
In the market place the term building products often refers to the
ready-made particles/sections, made from various materials, that are
fitted in architectural hardware and decorative hardware parts of a
building. The list of building products exclusively exclude the building
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materials, which are used to construct the building architecture and
supporting fixtures like windows, doors, cabinets, etc. Building products
do not make any part of a bajingo rather they support and make them
working in a modular fashion.
It also can refer to items used to put such hardware together such
as glues, caulking, paint, and anything else bought for the purpose of
constructing a building.
Exercise 2. Match the building material with its definintion:
1. Concrete… a) ... vary immensely in heat tolerance hardness
and resiliency.
2. Metal… b) ... has been the predominant building material in this modern age due to its longevity,
formability, and ease of transport.
3. Glass… c) ... are made of hydrated cement paste that
binds wood or alike particles or fibers to make
pre-cast building components.
4. Plastics… d) ... is used as structural framework for larger
buildings such as skyscrapers, or as an external
surface covering.
5. Foam… e) ... is sandwiched between wood or cement or
insulated concrete forms.
6. Cement composites… f) ... is generally made from mixtures of sand
silicates, in a very hot fire stove called a kiln and
is very brittle.
Exercise 3. Answer the questions:
1. What are the components of Portland cement concrete?
2. How is the strengthened concrete called?
3. What are the advantages of concrete?
4. What are the properties of steel?
5. What is the metal’s prime enemy?
6. What metals are used for decoration?
7. What have windows been used since the invention of glass for?
8. What is the disadvantage of glass?
9. What property do the plastics have in their semi-liquid state?
10. What structural materials are used in combination with foam?
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11. What is wood-cement compatibility?
12. What are building products?
Task 4
Exercise 1. Look through the text and say what it is about in Russian:
Building materials and construction
Part 1
Civil Engineering consists of design; construction; maintenance;
inspection; management; of characteristically different/diverse public
work projects from rail, roads, bridges to high rise buildings to sewage
treatments pl
ants.
At the core of civil engineering rests the investigation of materials
and methods that can facilitate construction.
In order to choose the most appropriate and economic material,
an engineer must have comprehensive knowledge of properties and
manufacturing processes of various engineering materials.
The materials which are used for the construction purpose are called
building materials. Natural materials: clay, rocks, sand, wood, etc.
Man-made materials: concrete, glass, bricks, plastic, etc.
Properties of materials. Three main headings: physical; mechanical;
chemical. Others: thermal; acoustic; optical; magnetic; electrical.
Exercise 2. Answer the questions:
1. What does Civil Engineering consist of?
2. How can an engineer choose the most appropriate and economic
building materials?
3. What materials are called building materials?
4. What are the main groups of building materials?
5. What are the major properties of materials?
Exercise 3. Write a summary of the text.
Task 5
Exercise 1. Look through the text and say what it is about in Russian:
Part 2
Physical properties of building materials
Physical properties of building materials are:
Density.•
Bulk density.•
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Chemical Resistance.•
Coefficient of softening.•
Density index.•
Durability.•
Fire Resistance.•
Frost Resistance.•
Hygroscopicity.•
Porosity.•
Refractoriness.•
Spalling Resistance.•
Specific heat.•
Thermal Capacity.•
Thermal Conductivity.•
Water Absorption.•
Water Permeability.•
We• athering Resistance.
The density of a material helps to distinguish it from other materials.
Since mass is usually expressed in grams and volume in cubic centimeters,
density is expressed in grams/cubic centimeter.
Bulk density is a property of powders, granules, and other “divided”
solids, especially it is used in reference to soil and gravel. It is defined as
the mass of many particles of the material divided by the total volume
they occupy. The total volume includes particle volume, inter-particle
void volume and internal pore volume.
Bulk density is not an intrinsic property of a material; it can change
depending on how the material is handled.
For example, a powder poured into a cylinder will have a particular
bulk density. If the cylinder is disturbed, the powder particles will move
and usually settle closer together, resulting in a higher bulk density.
For this reason the bulk density of powders is usually reported both as
“freely settled” (or “poured” density) and “tapped” density (where the
tapped density refers to the bulk density of the powder after a specified
compaction process, usually involving vibration of the container).
Soil weight is most often expressed on a soil volume basis rather than
on a particle basis.
Bulk density is defined as the dry weight of soil per unit volume of
soil. Bulk density considers both the solids and the pore space; whereas,
particle density considers only the mineral solids.
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Hygroscopicity is the ability of a substance to attract and hold water
molecules from the surrounding environment. This is achieved through
either absorption or adsorption with the absorbing or adsorbing material
becoming physically “changed” somewhat, by an increase in volume,
stickiness, or other physical characteristic of the material, as water
molecules become “suspended” between the material’s molecules in the
process.
There are problems in construction due to hygroscopicity. Nitrate
and chloride salts (usually found in building structures) are hygroscopic,
causing them to retain moisture and absorb additional moisture at times
of high humidity. Nitrate and chloride salts most commonly originate
in the ground. Their presence in plasterwork is usually an indication
of rising damp, lateral penetrating damp or flood damage. Coastal
properties may suffer from chloride salt contamination due to the salt
water carried in the air.
It is important when re-plastering a wall affected by salts that careful
consideration is given to the type of plaster used. The water content of
new plaster encourages salts to migrate from the underlying wall structure
to the new plaster resulting in further problems. Chemicals are available
to neutralize problematic salts before re-plastering work is undertaken.
Exercise 2. Match two parts of the sentenses:
1. The density of material … a) is the ability of a substance to attract and hold
water molecules from the surrounding environment.
2. Bulk density is … b) ... helps to distinguish it from other materials.
3. Bulk density considers … c) ... both the solids and the pore space.
4. Particle density consid-
ers …
5. Hygroscopicity … e) ... only the mineral solids.
d) ... a property of powders, granules and other
“divided” solids, especially it is used in reference
to soil and gravil.
Exercise 3. Answer the questions:
1. What are the physical properties of building materials?
2. What is bulk density?
3. How can bulk density change?
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4. What is the difference between bulk density and particle density?
5. What is hygroscopicity?
6. What are the problems in construction due to hygroscopicity?
How can the engineer solve these problems?
Exercise 4. Make a tree diagram of the text depicting the main ideas of
the text. Have a talk about physical prosperities of the building materials.
Task 6
Exercise 1. Read the text and answer the following questions:
Part 3
Mechanical and chemical properties of building materials
Mechanical Properties are: abrasion; creep; elasticity; fatigue;
hardness; impact; strength; plasticity and brittleness; strength; wear.
Mechanical properties of a few building materials:
Hardness of diamond. •
Ductility of copper. •
Elastic behaviour of rubber. •
Cement and bricks – strong in compression.•
Wood and steel – strong in tension.•
The chemical properties suggest the tendency of a material to
combine with other substances, its reactivity, solubility, effects like
corrosion, chemical composition, acidity, alkalinity, etc.
Exercise 2. Answer the questions:
1. What are the mechanical properties of building materials?
2. What are the mechanical properties of a few building materials?
3. What do the chemical properties of building materials suggest?
Exercise 3. Say about mechanical and chemical properties of the
building materials.
Task 7
Exercise 1. Read the text:
Part 4
Other properties of building materials
Thermal properties. These represent the behaviour of a material under
heat and temperature. Coefficient of thermal expansion of concrete is
fundamental in assessing the expansion potential of concrete slabs.
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Acoustical properties. Architectural acoustics deals with the
construction of enclosed areas so as to enhance the hearing of speech or
music. Properties such as sound transmission and sound reflection are
critical in choosing materials that should offer sound resistance.
For example, acoustic panel foam has following characteristic
features: high performance absorber; increased absorptive surface area;
fiber free; Class A fire retardant.
Absorptive/noise barrier quilted curtains have following
characteristics features: cost effective room dividers; water and chemical
resistant; exterior applications.
Optical properties. When light strikes any material, it interacts with
its atoms and causes various types of effects. The light may be either
reflected, refracted, scattered or absorbed. The study of light in materials
and how to use this behavior to control the various light effects is called
optics.
Optical properties such as colour, light transmission and light
reflection are considered while selection for construction purposes.
Exercise 2. Complete the sentences:
1. Thermal properties
represent …
2. Acoustical properties … b) ... such as sound transmission and sound re-
3. Optics is … c) ... colour, light transmission and light reflec-
4. Optical properties are … d) ... the behaviour of a material under heat and
a) ... the study of light in materials and how to
use this behaviour to control the various light effects.
flection are critical in choosing materials that
should offer sound resistance.
tion.
temperature.
Exercise 3. Imagine that you are a senior engineer in the construction
company. Answer the questions of the reporters about thermal, optical
and acoustical properties of the building materials.
Task 8
Exercise 1. Look through the text and say what it is about in Russian:
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Classification of Building materials
There are main three groups of building materials:
Cement materials (lime, cement, mortar, etc.).•
Protective materials (paints, varnishes, plaster, etc.).•
Solid materials (stones, bricks, iron, timber, etc.).•
Selection of materials. The selection criteria are: strength; durability;
appearance; availability and manufacturability; economic/cost effective;
environment friendly.
Strength. The material should be able to carry the design loads. It
should have adequate strength to resist failure under the action of stresses
caused by load. For example, concrete used as foundation slab should
be able to carry the load from the superstructure and pass it on to the
ground below safely and without settlement. A wooden beam supporting
timber floor should be strong enough to transfer the floor loads to the
supporting walls.
Durability. The material should satisfy serviceability requirements
such as: deformation limits; durability aspects; constraints on
performance; adaptability.
Serviceability implies satisfactory performance at all times. Recorded
data on past performance, laboratory test results and established practices
will help assess the serviceability of materials. For example, a material
whose surface is slick and slippery when moist is a poor choice for paving
roads. A road surface needs materials that show little movement under
the impact of loads, water resistant and easy to repair.
Appearance. Most nonstructural materials such as floor coverings,
paints, doors, windows are chosen based on aesthetic considerations.
The same is considered for some structural materials as well. A concrete
wall may be given different finishes depending on aesthetic appeal.
The masonry of buildings can be chosen to suitably match the ambient
architecture.
Availability/Manufacturability. Availability and manufacturability
requirements are often unseen limiting factors in materials selection.
The importance of a material being available is obvious. Materials which
are not available cannot be used. The importance of processibility is not
always so obvious.
Any other desirable qualities are useless if a material cannot
be processed into the shape required to perform its function. Most
engineering materials in use today have well known substitutes which
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would perform better and often at lower cost but processes for forming,
cutting, machining, joining are not available or commercially viable.
There is often a period of time after a new material is introduced during
which its application is severely limited while processing techniques are
developed which facilitate its use.
Environment friendly. Building materials typically considered to be
“green” include rapidly renewable plant materials like:
— bamboo and straw, dimension stone, recycled stone, recycled
metal;
— other products that are non-toxic, reusable, renewable, and/or
recyclable: sheep wool, panels from paper flakes, compressed
earth block, baked earth, rammed earth, clay, cork, coconut,
wood fibre plates, calcium sand stone, concrete (high and ultra
high performance) roman self-healing concrete.
Adobe is a very practical and resource efficient building method for dry
hot climates. Adobe is a natural building material made from sand, clay,
water and some kind of fibrous or organic material (sticks, straw, and/or
manure), which the builders shape into bricks using frames and dry in the
sun. Adobe buildings are similar to cob and mudbrick buildings.
Cob is a very old method of building with earth and straw or other fibers.
Recycled granite pavers provide a durable and beautiful alternative to concrete
or asphalt for patios, walkways, driveways, fountains, even streets.
Dimension stone is any type of natural rock material that is quarried
in order to make blocks or slabs of rock that are cut to specific sizes
(width, length, and thickness) and shapes. Dimension stone is used
because it is durable, strong and attractive.
Cost. Cost/economic restraint is one of the key factors governing the
choice of material. For example, timber construction is cheaper in the
United States but prohibitively expensive in many other countries.
A material’s cost is also generally a limiting factor. While cost
is universally recognized and perhaps the easiest of all properties to
understand there are specific cost considerations for materials selection.
Just as materials and their processing go hand in hand, so do material
costs and processing costs. Understanding the entire processing sequence
is critical to accurately evaluating the true cost of a material.
Standardization. When we use a construction material in any civil
engineering project a number of questions come up. For example: If we
are designing a concrete footing to anchor, the questions may include:
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