undefined | unit 1 building material and building construction

BCE

Unit 1

Building Material and Building Construction

Q1) Explain Scope Of Civil Engineering?

A1) Civil Engineering is that field of engineering concerned with planning, design and construction for environmental Control, development of natural resources, buildings, transportation facilities and other structures required for health, welfare, safety, employment and pleasure of mankind"

The main scope of civil engineering or the task of civil engineering is planning, designing, estimating, supervising construction, managing construction, execution, and maintenance of structures like building, roads, bridges, dams, etc. ' One who designs and maintains works of public utility is known as civil engineer. Civil engineer should have qualities like scientific attitude, imaginative and intuitive approach, He should have good analysis and decision power. He should be able to solve engineering problems, by using mathematical modelling, scientific principles and laboratory techniques using computer and information technology. He should be able to use operation research techniques for solution of management problems.

Q2) Explain Role of Engineers in the infrastructure development?

A2) A civil engineer has to conceive, plan, estimate, get approval, create and maintain all civil engineering activities.

Civil engineer has very important role in the development of the following infrastructure:

Measure and map the earth’s surface.

Plan new townships and extension of existing towns

Build the suitable structures for the rural and urban areas for various utilities

Build tanks and dams to exploit water resources.

Build river navigation and flood control projects.

Provide and maintain communication systems like roads, railways, harbours and airports

Purify and supply water to the needy areas like houses, schools, offices etc.

Build canals and distributaries to take water to agricultural fields

Devise systems for control and efficient flow of traffic

Provide and maintain solid and waste water disposal system

Monitor land, water and air pollution and take measures to control them

Fast growing industrialization has put heavy responsibilities on civil engineers to preserve and protect environment

Q3) Define Bricks?

A3) Bricks: Bricks are small rectangular blocks that can be used to form parts of buildings, typically walls. The use of bricks dates back to before 7,000 BC, when the earliest bricks were formed from hand-moulded mud and dried in the sun. During the Industrial Revolution, mass-produced bricks became a common alternative to stone, which could be more expensive, less predictable and more difficult to handle.

Bricks are still in common use today for the construction of walls and paving and for more complex features such as columns, arches, fireplaces and chimneys. They remain popular because they are relatively small and easy to handle, can be extremely strong in compression, are durable and low maintenance, they can be built up into complex shapes and can be visually attractive.

However, more recently, other materials have been developed that can be used as alternatives for building walls or for cladding facades and for some building types, particularly larger buildings, bricks can be seen as time consuming, expensive (although this is disputed by the Brick Development Association), structurally limiting, and requiring too much on-site labour. Some of these difficulties have been overcome by the introduction of reinforcement systems and by the development of pre-fabricated brick panels.

Q4) Explain Constituents of good brick earth?

A4) Bricks are the most commonly used construction material. Bricks are prepared by moulding clay in rectangular blocks of uniform size and then drying and burning these blocks. In order to get a good quality brick, the brick earth should contain the following constituents.

Silica

Alumina

Lime

Iron oxide

Magnesia

Q5) Define Stone?

A5) The process of taking out stones from natural rock beds is known as the quarrying. The term quarry is used to indicate the exposed surface of natural rocks. The stones, thus obtained, are used for various engineering purposes. The difference a mine and quarry should be noted. In case of a mine, the operations are carried out under the ground at great depth. In case of quarry, the operations are carried out at ground level in an exposed condition.

SITE FOR QUARRY-

The selection of site for a quarry of stones should be done after studying carefully the following aspects:

1. Availability of tools, power, materials and labour for the efficient working of quarry.

2. Easy availability of clean water in sufficient quantity all the year round.

3. Economy in quarrying.

4. Drainage of quarrying pit.

5. Facility of carrying and conveying stones from quarry.

6. Quality of stone available from quarry.

Aggregate

Construction aggregate, or simply aggregate, is a broad category of coarse- to medium-grained particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geo synthetic aggregates. Aggregates are the most mined materials in the world. Aggregates are a component of composite materials such as concrete and asphalt concrete; the aggregate serves as reinforcement to add strength to the overall composite material. Due to the relatively high hydraulic conductivity value as compared to most soils, aggregates are widely used in drainage applications such as foundation and French drains, septic drain fields, retaining wall drains, and roadside edge drains. Aggregates are also used as base material under foundations, roads, and railroads. In other words, aggregates are used as a stable foundation or road/rail base with predictable, uniform properties (e.g. to help prevent differential settling under the road or building), or as a low-cost extender that binds with more expensive cement or asphalt to form concrete.

Q6) Define Cement? And explain tests for cement, uses of cement, types of cement?

A6) Cement: Cement is a binder, a substance that sets and hardens and can bind other materials together. Cements used in construction can be characterized as being either hydraulic or non-hydraulic, depending upon the ability of the cement to be used in the presence of water. Non-hydraulic cement will not set in wet conditions or underwater, rather it sets as it dries and reacts with carbon dioxide in the air. It can be attacked by some aggressive chemicals after setting. Hydraulic cement is made by replacing some of the cement in a mix with activated aluminium silicates, pozzolanas, such as fly ash. The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water and safe from chemical attack. This allows setting in wet condition or underwater and further protects the hardened material from chemical attack (e.g., Portland cement).

Use

Cement mortar for Masonry work, plaster and pointing etc.

Concrete for laying floors, roofs and constructing lintels, beams, weathershed, stairs, pillars etc.

Construction for important engineering structures such asbridge, culverts, dams, tunnels, light house, clocks, etc.

Construction of water, wells, tennis courts, septic tanks, lamp posts, telephone cabins etc.

Making joint for joints, pipes, etc.

Manufacturing of precast pipes, garden seats, artistically designed wens, flower posts, etc.

Preparation of foundation, water tight floors, footpaths, etc.

Types of Cements

Many types of cements are available in markets with different compositions and for use in different environmental conditions and specialized applications. A list of some commonly used cement is described in this section:

Ordinary Portland cement

Ordinary Portland cement is the most common type of cement in general use around the world. This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450°C in a kiln, in a process known as calcinations, whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide, or quicklime, which is then blended with the other materials that have been included in the mix. The resulting hard substance, called 'clinker', is then ground with a small amount of gypsum into a powder to make 'Ordinary Portland Cement'(often referred to as OPC). Portland cement is a basic ingredient of concrete, mortar and most non-specialty grout. The most common use for Portland cement is in the production of concrete. Concrete is a composite material consisting of aggregate (gravel and sand), cement, and water. As a construction material, concrete can be cast in almost any shape desired, and once hardened, can become a structural (load bearing) element. Portland cement may be grey or white.

Rapid hardening Portland cement

It is firmer than Ordinary Portland Cement

It contains more C3S are less C2S than the ordinary Portland cement.

Its 3 days strength is same as 7 days strength of ordinary Portland cement. Low heat Portland cement

Heat generated in ordinary Portland cement at the end of 3days 80 cal/gm. While in low heat cement it is about 50cal/gm of cement.

It has low percentage of C3A and relatively more C2S and less C3S than O.P. Cement.

Reduce and delay the heat of hydration. British standard ( B S. 1370 : 1974 ) limit the heat of hydration of this cement.

Sulphate resisting Portland cement

For this cement, the silage as obtained from blast furnace is used

The clinkers of cement are ground with about 60 to 65 percent of slag.

Its strength in early days is less and hence it required longer curing period. It proves to be economical as slag, which is a Waste product, is used in its manufactures.

Pozzolanic cement

As per Indian standard, the proportions of Pozzolana may be 10 to 25 % by weight. e.2. Burnt clay, shale, Fly ash.

This Cement has higher resistance to chemical agencies and to sea water because of absence of lime.

It evolves less heat and initial strength is less but final strength is 28 days onward equal to ordinary Portland cement.

It possesses less resistance to the erosion and weathering action.

It imparts higher degree of water tightness and it is cheap.

White Portland cement

Grey colour of O.P. cement is due to presence of Iron Oxide. Hence in White Cement Fe, O, is limited to 1 %. Sodium Alumina Ferrite (Crinoline) NavAlF6 is added to act as flux in the absence of Iron-Oxide.

It is quick drying, possesses high strength and has superior aesthetic values and it also cost lee than ordinary Cement because of specific requirements imposed upon the raw materials and the manufacturing process. White Cement are used in Swimming pools, for painting garden furniture, moulding sculptures and statues etc.

Coloured Portland Cement

The Cement of desired colour may be obtained by mixing mineral pigments with ordinary Cement.

The amount of colouring material may vary from 5 to 10 percent. If this percentage exceeds 10percent, the strength of cements is affected.

The iron Oxide in different proportions gives brown, red or yellow colour. The coloured Cement are widely used for finishing of floors, window sill slabs, stair treads etc.

Expansive cement

This type of cement is produced by adding an expanding medium like sulpho aluminate and a stabilising agent to the ordinary cement.

The expanding cement is used for the construction of water retaining structures and for repairing the damaged concrete surfaces.

High alumina cement

This cement is produced by grilling clinkers formed by calcining bauxite and lime. It can stand high temper lures.

If evolves great heat during setting. It is therefore not affected by frost.

Q7) Define RCC?

A7) Reinforced cement concrete

Reinforced concrete (RC) (also called reinforced cement concrete or RCC) is a composite material in which concrete's relatively low tensile strength and ductility are counteracted by the inclusion of reinforcement having higher tensile strength or ductility. The reinforcement is usually, though not necessarily, steel reinforcing bars (rebar) and is usually embedded passively in the concrete before the concrete sets.

Q8) What Is Pre-stressed concrete?

A8)

Pre-stressed concrete sections are thinner and lighter than RCC sections, since high strength concrete and steel are used pre-stressed concrete.

In pre-stressed concrete, whole concrete area is effective in resisting loads, unlike RCC where concrete below the neutral axis is neglected.

Thinner sections in pre-stressed concrete results in less self weight and hence overall economy.

Long span bridges and flyovers are made of pre-stressed concrete because of lesser self weight and thinner section. So, pre-stressed concrete is used for heavily loaded structures.

Pre-stressed concrete members show less deflection.

Since the concrete does not crack in pre-stressed concrete, rusting of steel is minimized.

Pre-stressed concrete is used in the structures where tension develops or the structure is subjected to vibrations, impact and shock like girders, bridges, railway sleepers, electric poles, gravity dams, etc.

Precast members like electric poles and railway sleepers are produced in factories using simple pre-stressing methods.

Q9) Explain PCC and RCC?

A9) Plain cement concrete is generally used for the foundation. However, its other uses are:

As bed concrete below the wall footings, column footings and on walls below beams.

As sill concrete to get a hard and even surface at window and ventilator sills.

As to coping concrete over the parapet and compound walls.

For flagging the area around the buildings.

To make pavements.

To make tennis courts, basketball courts etc.

Plinth Protection

Storm/ Sewer at drains, small retaining walls.

RCC

Its full name is reinforced cement concrete, or RCC. RCC is concrete that contains steel bars, called reinforcement bars, or rebars. This combination works very well, as concrete is very strong in compression, easy to produce at site, and inexpensive, and steel is very very strong in tension.

To make reinforced concrete, one first makes a mould, called formwork, that will contain the liquid concrete and give it the form and shape we need. Then one looks at the structural engineer's drawings and places in the steel reinforcement bars, and ties them in place using wire. The tied steel is called a reinforcement cage, because it is shaped like one. Once the steel is in place, one can start to prepare the concrete, by mixing cement, sand, stone chips in a range of sizes, and water in a cement mixer, and pouring in the liquid concrete into the formwork tilll exactly the right level is reached.

The concrete will become hard in a matter of hours, but takes a month to reach its full strength. Therefore it is usually propped up until that period. During this time the concrete must be cured, or supplied with water on its surface, which it needs for the chemical reactions within to proceed properly.

Q10) What are the different Types of steels used in civil engineering works?

A10) 1. Plain Carbon Steel or Mild Steel

This is the most common type of steel used in building construction, which is also known as mild steel. It is incalculably strong and durable, and ensures a sturdy built. Due to the strength that carbon steel provides, it is hugely useful in buildings and has proved to be of great advantage. It does not crack when bent, it is immensely flexible, and it is ductile and has great plasticity, along with the fact that it can endure calamities like earthquakes without it causing cracks in the steel. This is the most advantageous factor of carbon steel. A steel building is hardly ever prone to collapse or destruct in any form. It can withstand any sort of calamity and is strong enough to not crack, in turn being able to save its occupants. Other construction materials might easily collapse or break down, but steel does not, and carbon steel is highly strong to survive any major problems. Low carbon steel consists of 0.05%-0.25% carbon approximately. This type of steel has two yield points. Low carbon steel is simpler to handle because of its ability of being handled by two yield points, wherein the first yield point is goes a little higher over the second, lower yield point. Mild steel has a density of 7.85 g/cm. Due to its weld ability, plain-carbon steel is higher in strength than any other. However, fire protection is very important in a steel building, and must be given due thought to. Other than that steel construction causes no concerning issues.

2. Rebar Steel

More commonly known as reinforcing steel, this type of steel is used as a tension device for reinforced concrete or reinforced masonry structure. It is created out of carbon steel, with ridges given to it for mechanical anchoring in a better way in the concrete. It holds the concrete into compression, and it is available in various types of grades, which are usually found in varying specifications in yield strength, vital tensile strength, chemical composition, and elongation percentage. It provides resistance, durability and aesthetic resistance with local resistance and stiffness that spreads through a wide area that other types of steel aren’t usually equipped in. It has immense expansion potential and comes in various sizes depending on the country and construction. With its recyclable tendencies, rebar is proven to be very useful. The grades and specifications provide varied types in rebar as well, for instance, there is plain steel wire that is used for concrete reinforcement, aside from epoxy coated steel bars for reinforcement, plain bars and rail steel deformed bars, steel and zinc coated bars, low-alloy steel, stainless steel, axel steel, welded deformed steel, fabricated deformed steel bar mats, chromium, low carbon steel bars etc.

3. Structural Steel

Structural steel shapes are made out of this kind of steel, which is formed out of a precise cross section, at the same time it follows definite standards for mechanical properties and chemical composition. Structural steel comes in various shapes like I-Beam, Z shape, HSS shape, L shape (angle), structural channel (C-beam, cross section), T shaped, Rail profile, bar, rod, plate, open joist of web steel etc. Standard structural steel varies in different countries with different specifications. For example, European I-beam is Euronorm 19-57; structural steel in USA comes in carbon, low alloy, corrosion resistant high strength low alloy, quenched and tempered alloy steel etc. Structural steel is ductile, strong, durable, and it can be morphed into almost any shape based on the construction; it can be constructed almost immediately the moment it is received at the construction site. Structural steel is fire resistant in itself but fire protection should be provided in case there is a possibility of it getting heated up to a point where it starts to lose its strength. Corrosion must be prevented when it comes to structural steel, but tall buildings are known to have withstood various kinds of calamities when built using structural steel.

Sign Up