Various types of Materials used in Construction

Guru

Introduction

The process and art of construction is an elaborate swerve between architect, engineering, and matarial selection. However, one of the most important decisions related to a construction project is to select the appropriate materials because that directly determines the longevity, efficacy, and utility of the structure. In this blog, we will examine the wide range of materials used in construction – from the classic to the modern, the unique features of each substance, the various roles they play in the built environment, as well as their properties.

 

Materials of Construction

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

  1. Stones
  2. Bricks
  3. Sand
  4. Reinforcing steel
  5. Cement
  6. Plain cement concrete (PCC)
  7. Reinforced cement concrete (RCC)
  8. Prestressed concrete (PSC)
  9. Precast concrete

An introduction to smart materials is presented and need for recycling of
materials is discussed.

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.

Requirements of Good Building Stones

The following are the requirements of good building stones:

1.Strength: The stone should be able to resist the load coming on it. Ordinarilly this is not of primary concern since all stones are having good strength. However in case of large structure, it may be necessary to check the strength.

2.Durability: Stones selected should be capable of resisting adverse effects of natural forces like wind, rain and heat.

3.Hardness: The stone used in floors and pavements should be able to resist abrasive forces caused by movement of men and materials over them.

4.Toughness: Building stones should be tough enough to sustain stresses developed due to vibrations. The vibrations may be due to the machinery mounted over them or due to the loads moving over them. The stone aggregates used in the road constructions should be tough.

5.Specific Gravity: Heavier variety of stones should be used for the construction of dams, retaining walls, docks and harbours. The specific gravity of good building stone is between 2.4 and 2.8.

6.Porosity and Absorption: Building stone should not be porous. If it is porous rain water enters into the pour and reacts with stone and crumbles it. In higher altitudes, the freezing of water in pores takes place and it results into the disintegration of the stone.

7.Dressing: Giving required shape to the stone is called dressing. It should be easy to dress so that the cost of dressing is reduced. However the care should be taken so that, this is not be at the cost of the required strength and the durability.

8.Appearance: In case of the stones to be used for face works, where appearance is a primary requirement, its colour and ability to receive polish is an important factor.

9.Seasoning: Good stones should be free from the quarry sap. Laterite stones should not be used for 6 to 12 months after quarrying. They are allowed to get rid of quarry sap by the action of nature. This process of removing quarry sap is called seasoning.

10.Cost: Cost is an important consideration in selecting a building material. Proximity of the quarry to building site brings down the cost of transportation and hence the cost of stones comes down.

However it may be noted that not a single stone can satisfy all the requirements of a good building stones, since one requirement may contradict another. For example, strength and durability requirement contradicts ease of dressing requirement. Hence it is necessary that site engineer looks into the properties required for the inteded work and selects the stone.

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.For the construction of sturdy and strong buildings, excellent in quality building bricks are necessary. For a building to be stable and durable, the bricks used are extremely important. A quality building brick must meet the following requirements:

Requirements of Good Building bricks

1. High Compressive Strength: The brick creates used in the constructions of housing units should have high compressive resistance to the endure the load carrying specifications of a structure. The corresponding compressive strength is a material’s resistance to crush under vertical load conditions.
2. Low Water Absorption: The brickwork must have its water absorption reduced immensely in order to prevent them from disintegrating in the face of moisture. An undesired growth of water leads to efflorescence, freeze- thaw damage, and diminished strength.
3. Uniform Size and Shape: Regularity in size and shape is necessary for the work of production. The use of uniform bricks will make the alignment of the project straighter and thereby easier, thus presenting appearance in an aesthetic way while building a structurally sound entity.
4. Hardness and Durability: Bricks are supposed to be both hard as well as tough and durable enough to cope with wear and tear appearing over time. Their ability to resist abrasion and weathering is partly attributable to the bricks hardness.
5. Sound Insulation: Ideally, good building bricks should offer appropriate soundproofing to help reduce sound transmission from one part of the building to another. This is particularly true for the residential and business purpose built premises.
6. Thermal Insulation: Insulating bricks help in maintaining the indoor temperature as well as reducing the energy consumption of the building. It matters both for comfortable and energy efficiency.
7. Fire Resistance: Bricks have the capacity to withstand a fire which is very important to the safety of the person who stays in the building. By using fire-resistant bricks, a fire could be confined, and further spread of the fire may be prevented.
8. Low Efflorescence: It is often observed in structural masonry, efflorescence refers to the formation of white powdery material on the surface of brick caused by the migration of soluble salts. Bricks are deemed to be good if the level of efflorescence is low so as the look of the bricks remains the same and it can withstand the external forces.
9. Color and Texture: Although unrelated to structural properties, color and texture of bricks contribute to overall aesthetic values brought by a structure.The construction has an appealing texture and uniform color that add to its visual appeal.
To ensure the construction of a secure, long-lasting, and attractive building, it is important to take all of these factors into account when choosing building bricks. Before being used for construction projects, the quality of the bricks can be confirmed by testing and adhering to applicable standards.

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.For many construction uses, particularly for mortar and concrete mixtures, high-quality building sand is important. The properties of high-quality building sand help to the materials' strength, workability, and a long life. These are the fundamental elements of high-quality building sand.

Requirements of Good Building sand

1. Gradation: The sand grains should be from well graded type as this is a mixture of different sizes. As the workability of mortar and concrete is improved by having a well-graded formulation sand mix, providing sufficient large particles which is in good proportion to smaller particles.
2. Particle Shape: The morphology of sand particles determines workability and strength in constructions. In the best case scenario the mix of sand should have angular or sub angular grains that give good interlocking and cohesion in this blend.
3. Cleanliness: Over all, building sand should be free of contaminants–clay, silt, organic material, and other harmful impurities. Presence of impurities weakens the bonding nature of the mortar which can only cause problems with the strength of the construction.
4. Silt Content: The presence of too much silt in sand makes the construction material less and poorly workable and loses strength. From a quality of the sand standpoint, low silt content is desirable.
5. Clay Content: Same as in case of silt, high clay content from sand reduces the properties of mortar and concrete. Too much clay cause shrinkage, cracking and less durability.
6. Moisture Content: It should be moist enough. The over moist mortar and concrete may be more difficult to achieve a required consistency, whereas aggravated dry sand may produce workability without.
7. Consistency: The properties of good properly defined should remain uniform as from batch to batch. The consistency ensures predictable and reliable performance in construc- tion domains.
8. Color: Though not a performance parameter, the color of the sand may be of consideration when exposed concrete or decorative applications in view.
9. PH Level: To ensure that other materials employed during the process of construction do not react adversely with sand, it a suitable pH level should be maintained; such level should not be harmful.
It is advisable to get samples and run tests before buying building sand to make sure it satisfies the requirements for the particular construction application. Using high-quality building sand in construction projects can be promised by communicating with engineers and following local building codes.

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.
While talking about to the durability and stability of reinforced concrete structures, high-quality reinforcing steel, or rebar, is important. The following requirements are necessary for high-quality reinforcing steel construction.

Requirements of Good Building reinforced steel

1. High Strength: The tensile force that is applied to a structure will generate tensile stress and for reinforcing steel to remain useful, this reinforcing steel has to have high tensile strength. Standard Classes of reinforcing steel are Grade 60 and Grade 40, which translate to their minimum yield strength in ksi (thousands of psi).
2. Ductility: Ductility is the capacity of reinforcing steel not to break when deforming. This factor is pivotal for redistributing stress across the body and avoiding brittle fracture within the direction of structures. The ductile rebar permits some stretching before yielding.
3. Weldability: The connection of the different bars through forming forming a sturdy structure requires that the reinforce steel is weldable. In such dangerous structures as complex configurations, weldability is crucial.
4. Bendability: Each piece of rebar should bend well with no cracks allowed. This feature is very important during construction proper arrangement during which bars have to be shaped to fit the particular design dictates of a structure.
5. Corrosion Resistance: It is typically subjected to atmospheric influences containing moisture and hostile chemicals, thus inducing corrosion. The quality good rebar should have the corrosion-resistant coating or made of corrosion-resistant material to pass this factor in order to ensure long-yielding.
6. Bond Strength: Only the links among reinforcing steel and surrounding concrete are of importance for transmission of forces. The rebar it should provide bond strength, sufficient to establish good co-operation between the two materials.
7. Consistent Quality: Steady quality should be obtained from the process of manufacturing grade 35/45 and others including reinforced steel. This guarantees equal mechanical characteristics and dimensions which are critical for the predictability and credibility of the reinforced concrete structures.
8. Identification Markings: Details such as the manufacturer’s identification, whether Grade 3 or above and any other matter pertinent should be clearly written with each bar. This assists in quality control, traceability and such ensuring compliance with the design requirements.
9. Compliance with Standards: The specifications and industry standards that apply to reinforcing steel should be followed, such as those established by ASTM International or other national and international standards organizations.Making sure compliance confirms that the information fulfills established criteria for performance.
Based on the specific requirements of a construction project, engineers and contractors must carefully choose reinforcing steel. The use of premium reinforcing steel in reinforced concrete structures can be guaranteed by routine testing and adherence to industry standards.

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 250 N/`mm^2` and young’s modulus 2 × 105 N/`mm^2`. 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/`mm^2`. 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/`mm^2` to 1900 N/`mm^2`. 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.Constructing durable and stable buildings requires the use of high-quality cement. The strength of concrete and its durability are mainly determined by its cement properties. The fundamental requirements of high-quality building cement are listed below.

Requirements of Good Building cement

1. Chemical Composition: Cement has a clearly defined chemical makeup which mainly includes calcium, silicon, aluminum and iron. The first and second aids comply with certain proportions to provide specific properties in concrete.
2. Fineness: The particle-size-related fineness of cement particles is vital for the reactivity and hydration of the cement. The strength and workability of concrete are achieved because of the larger surface area provided by finer particles in the concrete mix.
3. Setting Time: The cement should also have adjustable setting stage- the initial setting time and final setting time – to make sure that a long enough amount of time is provided for mixing, laying and finishing the final product. Various factors influence the setting time, for instance, temperature and type of cement.
4. Strength Development: Cement that is good should through a high early strength targeted with time strength development. This maintains that the concrete attains the necessary strength for structural purpose.
5. Soundness: Excessive hydration volume depends on accelerators or high-temperature setting that should be prevented during in the process of setting or hardening of cement. Soundness testing guarantees that the cement paste is stable and won’t cause cracking of the concrete due to shattering.
6. Consistency: The homogeneous state of composition of cement is what is referred to as the consistency of cement. In construction, consistent quality is essential for valuably, the patterns of performance and easy to operate with.
7. Heat of Hydration: There is an expectation that the amount of heat generated by the hydration process of cement should be within tolerable limits. Thermal cracking can be caused by high temperature and these cracks become persistent cracks which affect the long enduring strengths of this structure.
8. Low Clinker Content: Cement of better quality usually exhibits lower clinker content. The reduction in clinker content can reduce the amount of carbon released during the production process thereby making the cement green.
9. Color: Though the shade is not very important while the performance of the cement is concerned, it must remain uniform while opting for the product.This promises that the completed concrete will have an attractive look.
It is important to take these requirements and specifications into consideration when choosing cement for a building project. In order to be sure that cement performs constantly in concrete structures, quality control procedures, testing, and adherence to industry standards are essential.

Plain cement concrete (PCC)

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 (RCC)

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:
  • Footing
  • Columns
  • Beams, lintels
  • Chejjas, roof slabs
  • Stairs.

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

  • Water tanks
  • Dams
  • Silos, bunkers

   3. They are used for the construction of

  • Bridges
  • Retaining walls
  • Docks and harbours
  • Under water structures

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

  • Multistorey buildings
  • Chimneys
  • Towers

   5. R.C.C. is used for paving

  • High ways
  • City roads
  • 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.

Pre-Stressed 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

Conclusion

The need to select materials for construction is an essential decision that has implications on the lifespan, visual appeal, and functionality of a project. Traditional materials used in the industry include concrete, steel, and wood, and innovative materials that have been introduced are the FRPs, ICFs. The construction industry keeps changing due to sustainability and innovation. By choosing the appropriate materials together with sustainable practices, construction practitioners ensure the emergence of long-standing, performance-based, aesthetically pleasing edifices that define the world we live in.

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