Material of house construction

Various materials are used for constructing buildings, bridges, roads, retaining walls and dams.Use of the following materials of construction is presented in this article.

1. Stones

2. Bricks

3. Sand

4. Reinforcing steel

5. Cement

Material of house construction

6. Plain cement concrete (PCC)

7. Reinforced cement concrete (RCC)

8. Prestressed concrete (PSC)

9. Precast concrete and

STONE

Stone is a naturally available building material, which has been used from the early age of civilization. It is available in the form of rock, which is cut to the required size and shape and used as building block. Stone has been used to build small residential buildings to larges palaces,forts, temples and monuments. Rashtrapathi Bhavan, Jaipur Palace, Red Fort, Birla Mandirs at Delhi, Banaras and Hyderabad, Taj Mahal, Gateway of India and India Gate etc. are the world famous stone buildings.

The following is the list of uses of stone:

1. Stone masonry is used for constructing foundations, walls, columns and arches in a building.

2. Stones are used as flooring materials. Marble which is having good appearance is used as flooring material in luxurious buildings.

3. Stone slabs are used as damp proof courses, lintels and sometimes even as roofing material. 

4. Stones with good appearance are used for the face works of buildings. Polished marble and granite are commonly used materials for the face works.

5. Stones are used for paving of roads, foot path and open spaces around the buildings.

6. Crushed stones with murram are used to provide base course for roads. When very smaller pieces of stones are mixed with tar, it forms finishing coat of roads.

7. Crushed stones are used for the following:

(i) As a basic inert material (jelly/coarse aggregate) in concrete.

(ii) As railway ballast.

(iii) For making artificial stones and hollow building blocks.

8. Stones are also used in construction of piers and abutments of bridges.

9. Stone is commonly used as basic construction material in buildings, retaining walls and dams. However it is worth noting that the popularity of stones as building material is going down due to the following reasons:

1. Availability of stones within a reasonable distance from the cities is becoming scare. As a result of it, the cost of the stone at construction sites in cities is increasing.

2. Labour cost for handling and dressing of stones is high.

3. As the surfaces of stones are not uniform, mortar consumed in stone masonry is high.

4. Mortar bricks and hollow concrete blocks which are easy to handle and consume less mortar are becoming more popular.

5. R.C.C. and steel are more dependable materials for their uniformity of strength and hence designers prefer to use them for all important and big buildings.

BRICKS

Bricks are obtained by moulding good clay into blocks, which are dried and then burnt. This is the oldest building block to replace stone. Manufacture of bricks was started with hand moulding,sun drying and burning in clamps. A considerable amount of technological development has taken place with better knowledge of the properties of raw materials, use of better machineries and techniques of handling, drying and burning. Bricks are used for the following construction works:

1. As building blocks.

2. For lining of ovens, furnaces and chimneys.

3. To encase steel columns to protect them from fire.

4. For providing water proofing course to R.C.C. roofs.

5. For making footpaths and cycle tracks in cities.

SAND

Sand is used as a base course to place flooring tiles so as to get level surface. In construction works sand is mainly used as inert material in mortar and concrete.Sand is a natural product which is obtained as river sand, nalla sand and pit sand. Sea sand should not be used in making mortar and concrete for the following reasons:

1. It contains salt and hence structure remains damp. The mortar is affected by efflorescence and then blisters appear.

2. It contains shells and organic matter, which decompose after some time and reduce the strength and life of mortar and concrete.

Sand can be obtained artificially by crushing stones also. In crushing stones to get coarse aggregates, it is obtained as a by-product. The minute particles of crushed stones form artificial sand for construction activities. In constructing dams and bridges, artificial sand is very commonly used.

Sand is used in mortar and concrete for the following purpose:

1. It subdivides the paste of binding material into thin films and allows it to adhere and spread.

2. It fills up the gap between the two building blocks and spreads the binding material.

3. It adds to the density of mortars and concrete.

4. It prevents shrinkage of cementing material.

5. It allows carbon dioxide from the atmosphere to reach some depth and thereby improves there by setting power.

6. The cost of cementing material per unit volume is reduced as this low cost material increases the volume of cementing material.

7. Silica of sand contributes to formation of silicates resulting into hardened mass..

REINFORCING STEEL

Steel is an alloy of ferrous metal with 0.25 to 1.5 per cent of carbon. Higher the carbon content,harder is the steel. Steel bars of circular cross sections are mainly used as reinforcement to strengthen concrete structures. There are three types of reinforcing steel:

1. Mild steel

2. High Yield Strength Deformed bars (HYSD)/TOR steel and

3. High tensile steel.

 Mild Steel

It contains carbon upto 0.23 to 0.25%. Higher value is permitted for bars of 20 mm and above diameter. It is available in diameters of 6, 10, 12, 16, 20, 25 and 32 mm. Its yield strength is 250N/mm2 and young’s modulus 2 × 105 N/mm2. It was very commonly used reinforcement in concrete. But nowadays TOR steel is replacing it. It is used as window bars, for grills and for making steel gates.

 HYSD Bars/TOR Steel

Two types of TOR steel bars are available. They are Fe-415 and Fe-500. The number associated with the designation indicates the tensile strength of bar in N/mm2. These bars are provided with ribs deformation on surface so that bond between concrete and steel improves. These bars are available in diameters 8, 10, 12, 16, 20, 22, 25, 28 and 32 mm. Nowadays these bars are replacing mild steel bars as reinforcement since their strength in tension and bond is higher. These are also used as wind bars.

High Tensile Bars

High tensile steel bars are made with 0.8 % carbon and 0.6 % manganese apart from small percentages of silicon, sulphur and phosphorous. The process of making these wires involve cold drawing and tempering. They are usually available in 2, 3, 4, 5, 6, 7 mm diameters. They may be bundled with number of them to form a strand.These bars are having tensile strength as high as 1400 N/mm2 to 1900 N/mm2. The young’s modulus of steels is also same as that of mild steel.High tensile bars are used as reinforcement in prestressed concrete.

CEMENT

Cement is manufactured by calcifying calcarious material (lime) and argillaceous material (shale and clay) and then clinker so formed is ground to fine powder. Use of cement alone is limited to filling small cracks with its paste. It is mainly used as binding material in mortar and concrete.

PLAIN CEMENT CONCRETE

The intimate mixture of cement, sand, coarse aggregate (jelly) and water is known as plain cement concrete. A small quantities of admixtures like air entraining agents, water proofing agents,workability agents may also be added to impart special properties to the plain cement concrete.

Uses of plain cement concrete is listed below:

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

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

3. As coping concrete over the parapet and compound walls.

4. For flagging the area around the buildings.

5. For making pavements.

6. For making tennis courts, basket ball courts etc.

REINFORCED CEMENT CONCRETE

Concrete is good in resisting compressive stress but is very weak in resiting tensile stresses.Hence reinforcement is provided in the concrete wherever tensile stress is expected. The best reinforcing material is steel, since its tensile strength is high and bond between steel and concrete is good. Since elastic modulus of steel is quite high compared to concrete, the force developed in steel is high. A cage of reinforcements is prepared as per the design requirements, kept in the form work and then green concrete is poured. After the concrete hardens, the form work is removed. The composite material of steel and concrete, now called R.C.C. acts as a structural member and can resist tensile as well as compressive forces efficiently.

Uses of R.C.C.

1. R.C.C. is used as a structural member wherever bending of the member is expected. The common structural elements in a building where R.C.C. is used are:

(a) Footing

(b) Columns

(c) Beams, lintels

(d) Chejjas, roof slabs

(e) Stairs.

2. R.C.C. is used for the construction of storage structures like:

(a) Water tanks

(b) Dams

(c) Silos, bunkers

3. They are used for the construction of

(a) Bridges

(b) Retaining walls

(c) Docks and harbours

(d) Under water structures

4. R.C.C. is used for building tall structures like

(a) Multistorey buildings

(b) Chimneys

(c) Towers.

5. R.C.C. is used for paving

(a) High ways

(b) City roads

(c) Airports

6. R.C.C. is used in atomic plants to prevent radiation. For this purpose R.C.C. walls built are as thick as 1.5 m to 2.0 m.

PRESTRESSED CONCRETE (PSC)

In prestressed concrete elements, calculated compressive stresses are introduced in the zone wherever tensile stresses are expected when the element is put to use. Thus in bridge girders,bottom side of beam tensile stresses develop when deck slab is placed and vehicles start moving on the bridge. Hence before girder is placed in its position compressive stresses are introduced at bottom side. This is achieved by pulling the high tensile wires before concrete is poured in the form work of beam and releasing the pull only after concrete hardens (pretensioned prestress concrete). In another method, it may be achieved by providing a duct from end to end in the beam while casting the beam. Then high tensile wire is passed through the duct and after stretching,it is anchored to the ends of beams. This is called post-tensioning prestress beam. ACI committee defines prestressed concrete as the one in which internal stresses have been introduced such that the stresses resulting from given external loadings are counter-acted to a desired degree. Prestressed concrete is commonly used in making the following structural elements.

1. Beams and girders.

2. Slabs and grid floors.

3. Pipes and tanks

4. Poles, piles, sleepers and pavements.

5. Shell and folded plate roofs

PRECAST CONCRETE

Usually concrete structures are built by casting them in their final position in the site by providing form work, pouring concrete and then removing the form work. It is called as cast-in-situ construction. If concrete elements are cast in factories or elsewhere and transported to their final destination, they are called precast elements.Since the elements are cast in factories where controls are better, they are superior to cast in situ elements. However, the disadvantage is cost of transportation and achieving desired connections on site. Precast concrete is used in the following:

1. Pipes and tanks

2. Poles, piles, sleepers and pavement

3. Lintel beams

4. Beams and girders

5. Building blocks

6. Wall panels

7. Manhole covers