UNIT 1
Building Material and Building Construction
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.
Role of Engineers in the infrastructure development
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:
Fast growing industrialization has put heavy responsibilities on civil engineers to preserve and protect environment
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.
Constituents of good brick earth:
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.
STONES
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.
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
Sulphate resisting Portland cement
Pozzolanic cement
White Portland cement
Coloured Portland Cement
Expansive cement
High alumina cement
Concrete mix design is the procedure by which the proportions of constituent materials are suitably selected so as to produce concrete satisfying all the required properties for the minimum cost. Many attempts have been made to develop a reliable method for normal concrete mix design in various parts of the world ever since usage of concrete began as a structural material.
In addition to the foregoing problems, another difficulty, usually experienced in site and encountered in the mix design, is the assessment of workability. Workability has been used qualitatively to describe the ease with which the concrete can be mixed, transported, placed, compacted, and finished. Thus, workability is rather difficult to define precisely, because it is intimately related, among others, to the following: (a) mobility: that property which determines how easily the concrete can flow into the moulds and around the reinforcement, (b) stability: that property which determines the ability of the concrete to remain as a stable and coherent mass during concrete production, (c) compactability: that property of concrete which determines how easily concrete can be compacted to remove air voids, and (d) finish ability: that property which describes the easiness to produce the specified surface.
In sites, usually special experience and slump test results are used together to assess workability. Although the slump test is not sufficient to measure and describe the workability of concrete, it is the test used extensively in site work
Function of Water in Concrete
Three water serves the following purpose:
To wet the surface of aggregates to develop adhesion because the cement pastes adheres quickly and satisfactory to the wet surface of the aggregates than to a dry surface.
To prepare a plastic mixture of the various ingredients and to impart workability to concrete to facilitate placing in the desired position and
Water is also needed for the hydration of the cementing materials to set and harden during the period of curing.
The quantity of water in the mix plays a vital role on the strength of the concrete. Some water which have adverse effect on hardened concrete. Sometimes may not be harmless or even beneficial during mixing. So clear distinction should be made between the effect on hardened concrete and the quality of mixing water.
Workability
Workability of Concrete is a broad and subjective term describing how easily freshly mixed concrete can be mixed, placed, consolidated, and finished with minimal loss of homogeneity. Workability is a property that directly impacts strength, quality, appearance, and even the cost of labour for placement and finishing operations. But opinions don’t matter much when testing and documenting concrete properties, so how are these qualitative characteristics defined in quantitative terms? This blog post will cover everything you need to know about concrete workability, factors that can affect it, tests that define it, and slump testing equipment to test it.
Compaction in concrete
Compaction is the process which expels entrapped air from freshly placed concrete and packs the aggregate particles together so as to increase the density of concrete. It increases significantly the ultimate strength of concrete and enhances the bond with reinforcement. It also increases the abrasion resistance and general durability of the concrete, decreases the permeability and helps to minimise its shrinkage-and-creep characteristics. Proper compaction also ensures that the formwork is completely filled – ie there are no pockets of honeycombed material – and that the required finish is obtained on vertical surfaces. When first placed in the form, normal concretes, excluding those with very low or very high slumps, will contain between 5% and 20% by volume of entrapped air. The aggregate particles, although coated with mortar, tend to arch against one another and are prevented from slumping or consolidating by internal friction
Concrete mix design
A good concrete mix design creates the foundation of a sound infrastructure.
Concrete mix design involves a process of preparation in which a mix of ingredients creates the required strength and durability for the concrete structure. Because every ingredient in the mix consists of different properties, it’s not an easy task to create a great concrete mix. It is imperative that all ingredients be tested to determine their physical properties and the bearing capacity of the project location.
The ingredients to be tested: water, fine aggregate (sand), coarse aggregate, cement, chemicals, reinforcement, and soil.
The values of the physical properties obtained after testing will be used as the basis for all concrete mix design considerations. This will ensure the structure will be sound and prevent failure of the mix. It is important to note that the ingredients for the mix might vary from one project location to another, so the physical properties must be tested for the requirements specified for each location.
The common method of expressing the proportions of ingredients of a concrete mix is in the terms of parts or ratios of cement, fine and coarse aggregates. For e.g., a concrete mix of proportions 1:2:4 means that cement, fine and coarse aggregate are in the ratio 1:2:4 or the mix contains one part of cement, two parts of fine aggregate and four parts of coarse aggregate. The proportions are either by volume or by mass. The water-cement ratio is usually expressed in mass
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.
Pre-stressed concrete
STRUCTURAL STEEL CONSTRUCTION
Structural steel is a category of steel construction material that is produced with a particular cross section or shape, and some specified values of strength and chemical composition. Structural steel composition, strength, size, shape, strength, and storage are controlled in most advanced countries. The word structural steel includes a broad variety of low carbon and manganese steels that are used in great numbers for civil and marine engineering applications. Structural steels are manufactured in section and plate shapes and are normally used in bridges, buildings, ships, and pipelines.
Concrete types: PCC, RCC, Pre-stressed, Precast and Ready Mix Concrete
PCC
Plain cement concrete is generally used for the foundation. However, its other uses are:
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.
Types of steels used in civil engineering works
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.
MORTAR
Mortar is a bonding agent which is generally produced by mixing cementing or binding material (lime or cement) and fine aggregate (sand, surki, sawdust, etc.) with water. Mortar is used to bind different building blocks like bricks, stones, etc. It can also add a decorative pattern in brick or stone masonry.
Mortar, a bonding agent between building materials, is mainly a mixture of water, fine aggregate (sand, surki, etc) and binding material like cement, lime etc. The applications of mortar in various construction phase have made it a very important civil engineering material.
ENGINEERING PROPERTIES OF MORTAR
Cement: It should be fresh and free from adulteration. To know more about the properties of good cement read >> Properties of Good Cement
Lime: Lime must be well slaked.
Sand: Sand should be sharp, angular and porous. It should be free from salts and other impurities. Read>> Function of Sand in Mortar
Surki: Surki should be perfectly pure and free from foreign matter. It should be sufficiently fine to pass through the desired sieve
Mud: Mud should be free from adulteration.
Water: Water should be clean and free from salts and other impurities.
Floors
A floor is the bottom surface of a room or vehicle. Flooring is the general term for a permanent covering of a floor, or for the work of installing such a floor covering. A lot of variety exists in flooring and there are different types of floors due to the fact that it is the first thing that catches your eye when you walk into a house, as it spans across the length and breadth of the house. It is also the surface that goes through the most wear and tear, and that's why choosing the right material is of utmost importance.
Types of Floors
1. MUD FLOOR:
Earthen Flooring also commonly known as Adobe flooring is made up of dirt, raw earth or other unworked ground materials. In modern times, it is usually constructed with mixture of sand, clay and finely chopped straw.
Mud flooring is commonly constructed in villages where by using stabilizers the properties of the soil are enhanced by manipulating its composition by adding suitable stabilizers. The tensile and shear strength of the soil is increased and shrinkage is reduced.
2. BRICK FLOOR:
Brick flooring is one of the types of floors whose topping is of brick. These are easy to construct and repair but the surface resulting from these is not smooth and is rough, hence, easily absorbs and retains moisture which may cause dampness in the building.
3. TILE FLOOR:
The floor whose topping is of tiles is called tile floor. The tiles used may be of any desired quality, color, shape or thickness.
4. FLAGSTONE FLOOR:
The floors whose topping consists of stone slabs is called flagstone floor. The stone slabs used here may not be of the same size but should not be more than 75 cm length and not less than 35 cm in width and 3.8 cm in thickness.
5. CEMENT CONCRETE FLOOR:
The types of floors whose topping consists of cement concrete is called cement concrete floor or conglomerate floor. These floors consists of 2.5 cm to 5cm thick concrete layer laid over 10 cm thick base concrete and 10 cm thick clean sand over ground whose compaction and consolidation is done. These floors are commonly used these days.
6.TERRAZZO FLOOR:
Terrazzo is a composite material, poured in place or precast, which is used for floor and wall treatments. It consists of chips of marble, quartz, granite, glass, or other suitable material, poured with a cementations binder (for chemical binding), polymeric (for physical binding), or a combination of both.
Roofs
It may be defined as the uppermost part of the building, provided as a structural covering, to protect the building from weather. Structurally, a roof is constructed in the same way as an upper floor, though the shape of its upper surface may be different. Roof consists of structural elements which support roof is roof covering. The roof coverings may be A.C. sheets, G.I. sheets, wooden shingles, tiles, slab itself.
TYPES OF ROOF
Reference Books
