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Plain and reinforced cement concrete

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Arun Saini
Arun Saini

This document discusses the materials and design considerations for plain and reinforced concrete structures according to the National Building Code of India. It outlines the types of cement, aggregates, water, admixtures, and reinforcement that can be used. It also covers mix design and proportioning, durability requirements, and factors to consider when selecting reinforced concrete as a construction material such as its economy, suitability for structural and architectural functions, low maintenance needs, availability of materials, rigidity, and fire resistance.

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Structural Design Concrete Plain & Reinforced Cement Concrete By- Arun Saini B.Arch 7th sem.
A. Cement The cement used shall be any of the following conforming to accepted standards [6-5A(3)] and the type selected should be appropriate for the intended use: a) 33grade ordinary Portland cement b) 43 grade ordinary Portland cement c) 53 grade ordinary Portland cement d) Rapid hardening Portland cement e) Portland slag cement f) Portland pozzolana cement (fly ash based) g) Portland pozzolana cement (calcined clay based) h) Hydrophobic cement j) Low heat Portland cement k) Sulphate resisting Portland cement B. Mineral Admixtures Porzollanas Rice husk ash Fly ash (pulverized fuel ash) Metakaoline Silica fume Ground Granulated Blast Furnace Slag Materials
3. Aggregates Aggregates shall comply with the requirements of accepted standards [6-5A(7)]. As far as possible preference shall be given to natural aggregates. • Heavy weight aggregates or light weight aggregates such as bloated clay aggregates and sintered fly ash aggregates • Aggregate size can’t be greater than one-fourth of the minimum thickness of the member. For most work, 20 mm aggregate is suitable. 4. Water • Water use for mixing and curing shall be clean and free from injurious amounts of oils, acids, alkalis, salts, sugar, organic materials or other substances that may be deleterious to concrete or steel. • Potable water is generally considered satisfactory for mixing concrete. 5.Chemical Admixtures Admixture, if used shall comply with accepted standards [6-5A( 11)]. Previous experience with and data on such materials should be considered in relation to the likely standards of supervision and workmanship to the work being specified. • Admixtures should not impair durability of concrete nor combine with the constituent to form harmful compounds nor increase the risk of corrosion of reinforcement
6.Reinforcement The reinforcement shall be any of the following conforming to the accepted standards [6- 5 A(12)]: a) Mild steel and medium tensile steel bars. b) High strength deformed steel bars. c) Hard-drawn steel wire fabric. d) Grade A of structural steel. All reinforcement shall be free from loose mill scales, loose rust and coats of paints, oil, mud or any other substances which ‘may destroy or reduce bond. Sand blasting or other treatment is recommended to clean reinforcement.
NOTES 1 In the designation of concrete mix M refers to the mix and the number of the specified compressive strength of 150 mm size cube at 28 days, expressed in N/mm^2. Grade of concrete
DURABILITY OF CONCRETE General A durable concrete is one that performs satisfactorily in the working environment during its anticipated exposure conditions during service. The materials and mix proportions specified and used should be such as to maintain its integrity and, if applicable, to protect embedded metal from corrosion. The factors influencing durability include: a) the environment; b) the cover to embedded steel; c) the type and quality of constituent materials; d) the cement content and water/cement ratio of the concrete; e‘) workmanship, to obtain full compaction and efficient curing; and f) the shape and size of the member.
Plain and reinforced cement concrete
• CONCRETE MIX PROPORTIONING Information Required In specifying a particular grade of concrete, the following information shall be included: a) Type of mix, that is, design mix concrete or nominal mix concrete; b) Grade designation; c) Type of cement; d) Maximum nominal size of aggregate; e) Minimum cement content (for design mix f) concrete); g) Maximum water-cement ratio; h) Workability; i) Mix proportion (for nominal mix concrete); j) Exposure conditions as per Tables 4 and 5; k) Maximum temperature of concrete at the time l) of placing; m) Method of placing; and n) Degree of supervision.
Plain and reinforced cement concrete
Plain and reinforced cement concrete
Why Select Reinforced Concrete as Construction Material for a Structure? Factors that affect the choice of reinforced concrete over other construction material for building construction include: I. Economy II. Suitability of the material for structural and architectural functions III. Low maintenance IV. Availability of materials V. Rigidity VI. Fire resistance Economy of Reinforced Concrete In most cases, the overall cost of the structure is the first and most important factor that considered. Obviously, the cost of the structure made up of the cost of materials used for the construction, labor cost and time allocated for the construction of the structure. Comparatively, the thickness of concrete floor is smaller than that of steel structure. This is because floors are flat plates or flat slabs or beams and girder or joists are fitted within the same depth.
Consequently, the overall height of the structure is decreased, which is considerably desired, in comparison with steel floors. The reduction of the structure height would lead to decrease in wind force of the structure since the exposed area of the building to wind is lesser than that of steel structure. If the height of the building is decreased, then savings can be made in claddings and electrical and mechanical risers. There are cases in which the time allocated for the construction of the structure would control the entire cost of the structure. Because contractors need to assign specific budget for the construction, and they will not be able to take their investment back until the building is constructed. Therefore, it is might be more economical to consider fast construction and receive the investment sooner. This may offset the extra cost used for the formwork and extra material used. Reinforced concrete materials are broadly available and can be used and casted as per requirements. However, steel elements need to be ordered to be fabricated and should be paid partially in advance to arrange the job at steel fabricating yard. Any strategy that the designer use to standardize the design and forming will decrease the overall cost. For example, the same formworks can be used for all columns of the structure and using smaller concrete strength at upper storeys will reduce the overall cost of reinforced concrete construction.
Suitability of Reinforced Concrete for Structural and Architectural Functions It is possible to combine both architectural and structural functions in reinforced concrete system. Fresh concrete can be placed in any forms and shapes and desired textures can be provided through available finishing techniques. Not only does reinforced concrete structure is capable of serving its main purpose which is supporting loads but also it can provide aesthetically appealing appearances. The size and shape of reinforced concrete member is controlled by designer. Fig.1: Reinforced concrete support loads and provide aesthetically appealing appearances
Low maintenance of Reinforced Concrete Structures Generally, reinforced concrete structure does not require considerable maintenance compared to steel and timber structures. This advantageous side of reinforced concrete would be more obvious in the case when dense and air entrained concrete is used for exposed areas and sufficient drainage is provided Fig.2: Substantially old water tower reinforced concrete structure, still serve its purpose without the need of major maintenance
Availability of Materials for Reinforced Concrete The constituent of concrete such as sand, gravel and cement are widely available and steel bars are delivered to the construction site easily compared with case of steel element deliveries. That is why it is recommended to use reinforced concrete for building construction in remote areas. Fig.3: Reinforced Concrete Materials Available Widely Rigidity of Structures Commonly, reinforced concrete structure possesses great rigidity. That is why vibration problem does not frequently occur in reinforced concrete structures.
Fire resistance of Reinforced Concrete Structures should withstand fire for a period that is enough for the evacuation of the building and prevent the loss of lives and then control the fire. By and large, concrete structures can resist fire for a time ranges from 1 to 3 hours without the need of any special measures to improve building fire resistance. However, this is not the case for other construction materials such as timber and steel and hence they need to be fire protected to be able to withstand fire for specific time. This is a strong advantage of reinforced concrete that other construction materials are lacking. Fig.4: Reinforced concrete structure suffered from extreme fire and still stand and has not collapsed
NATIONAL BUILDING CODE OF INDIA PART 6 STRUCTURAL DESIGN Section 5 Concrete: 5A Plain and Reinforced Concrete References -

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Plain and reinforced cement concrete

  • 1. Structural Design Concrete Plain & Reinforced Cement Concrete By- Arun Saini B.Arch 7th sem.
  • 2. A. Cement The cement used shall be any of the following conforming to accepted standards [6-5A(3)] and the type selected should be appropriate for the intended use: a) 33grade ordinary Portland cement b) 43 grade ordinary Portland cement c) 53 grade ordinary Portland cement d) Rapid hardening Portland cement e) Portland slag cement f) Portland pozzolana cement (fly ash based) g) Portland pozzolana cement (calcined clay based) h) Hydrophobic cement j) Low heat Portland cement k) Sulphate resisting Portland cement B. Mineral Admixtures Porzollanas Rice husk ash Fly ash (pulverized fuel ash) Metakaoline Silica fume Ground Granulated Blast Furnace Slag Materials
  • 3. 3. Aggregates Aggregates shall comply with the requirements of accepted standards [6-5A(7)]. As far as possible preference shall be given to natural aggregates. • Heavy weight aggregates or light weight aggregates such as bloated clay aggregates and sintered fly ash aggregates • Aggregate size can’t be greater than one-fourth of the minimum thickness of the member. For most work, 20 mm aggregate is suitable. 4. Water • Water use for mixing and curing shall be clean and free from injurious amounts of oils, acids, alkalis, salts, sugar, organic materials or other substances that may be deleterious to concrete or steel. • Potable water is generally considered satisfactory for mixing concrete. 5.Chemical Admixtures Admixture, if used shall comply with accepted standards [6-5A( 11)]. Previous experience with and data on such materials should be considered in relation to the likely standards of supervision and workmanship to the work being specified. • Admixtures should not impair durability of concrete nor combine with the constituent to form harmful compounds nor increase the risk of corrosion of reinforcement
  • 4. 6.Reinforcement The reinforcement shall be any of the following conforming to the accepted standards [6- 5 A(12)]: a) Mild steel and medium tensile steel bars. b) High strength deformed steel bars. c) Hard-drawn steel wire fabric. d) Grade A of structural steel. All reinforcement shall be free from loose mill scales, loose rust and coats of paints, oil, mud or any other substances which ‘may destroy or reduce bond. Sand blasting or other treatment is recommended to clean reinforcement.
  • 5. NOTES 1 In the designation of concrete mix M refers to the mix and the number of the specified compressive strength of 150 mm size cube at 28 days, expressed in N/mm^2. Grade of concrete
  • 6. DURABILITY OF CONCRETE General A durable concrete is one that performs satisfactorily in the working environment during its anticipated exposure conditions during service. The materials and mix proportions specified and used should be such as to maintain its integrity and, if applicable, to protect embedded metal from corrosion. The factors influencing durability include: a) the environment; b) the cover to embedded steel; c) the type and quality of constituent materials; d) the cement content and water/cement ratio of the concrete; e‘) workmanship, to obtain full compaction and efficient curing; and f) the shape and size of the member.
  • 8. • CONCRETE MIX PROPORTIONING Information Required In specifying a particular grade of concrete, the following information shall be included: a) Type of mix, that is, design mix concrete or nominal mix concrete; b) Grade designation; c) Type of cement; d) Maximum nominal size of aggregate; e) Minimum cement content (for design mix f) concrete); g) Maximum water-cement ratio; h) Workability; i) Mix proportion (for nominal mix concrete); j) Exposure conditions as per Tables 4 and 5; k) Maximum temperature of concrete at the time l) of placing; m) Method of placing; and n) Degree of supervision.
  • 11. Why Select Reinforced Concrete as Construction Material for a Structure? Factors that affect the choice of reinforced concrete over other construction material for building construction include: I. Economy II. Suitability of the material for structural and architectural functions III. Low maintenance IV. Availability of materials V. Rigidity VI. Fire resistance Economy of Reinforced Concrete In most cases, the overall cost of the structure is the first and most important factor that considered. Obviously, the cost of the structure made up of the cost of materials used for the construction, labor cost and time allocated for the construction of the structure. Comparatively, the thickness of concrete floor is smaller than that of steel structure. This is because floors are flat plates or flat slabs or beams and girder or joists are fitted within the same depth.
  • 12. Consequently, the overall height of the structure is decreased, which is considerably desired, in comparison with steel floors. The reduction of the structure height would lead to decrease in wind force of the structure since the exposed area of the building to wind is lesser than that of steel structure. If the height of the building is decreased, then savings can be made in claddings and electrical and mechanical risers. There are cases in which the time allocated for the construction of the structure would control the entire cost of the structure. Because contractors need to assign specific budget for the construction, and they will not be able to take their investment back until the building is constructed. Therefore, it is might be more economical to consider fast construction and receive the investment sooner. This may offset the extra cost used for the formwork and extra material used. Reinforced concrete materials are broadly available and can be used and casted as per requirements. However, steel elements need to be ordered to be fabricated and should be paid partially in advance to arrange the job at steel fabricating yard. Any strategy that the designer use to standardize the design and forming will decrease the overall cost. For example, the same formworks can be used for all columns of the structure and using smaller concrete strength at upper storeys will reduce the overall cost of reinforced concrete construction.
  • 13. Suitability of Reinforced Concrete for Structural and Architectural Functions It is possible to combine both architectural and structural functions in reinforced concrete system. Fresh concrete can be placed in any forms and shapes and desired textures can be provided through available finishing techniques. Not only does reinforced concrete structure is capable of serving its main purpose which is supporting loads but also it can provide aesthetically appealing appearances. The size and shape of reinforced concrete member is controlled by designer. Fig.1: Reinforced concrete support loads and provide aesthetically appealing appearances
  • 14. Low maintenance of Reinforced Concrete Structures Generally, reinforced concrete structure does not require considerable maintenance compared to steel and timber structures. This advantageous side of reinforced concrete would be more obvious in the case when dense and air entrained concrete is used for exposed areas and sufficient drainage is provided Fig.2: Substantially old water tower reinforced concrete structure, still serve its purpose without the need of major maintenance
  • 15. Availability of Materials for Reinforced Concrete The constituent of concrete such as sand, gravel and cement are widely available and steel bars are delivered to the construction site easily compared with case of steel element deliveries. That is why it is recommended to use reinforced concrete for building construction in remote areas. Fig.3: Reinforced Concrete Materials Available Widely Rigidity of Structures Commonly, reinforced concrete structure possesses great rigidity. That is why vibration problem does not frequently occur in reinforced concrete structures.
  • 16. Fire resistance of Reinforced Concrete Structures should withstand fire for a period that is enough for the evacuation of the building and prevent the loss of lives and then control the fire. By and large, concrete structures can resist fire for a time ranges from 1 to 3 hours without the need of any special measures to improve building fire resistance. However, this is not the case for other construction materials such as timber and steel and hence they need to be fire protected to be able to withstand fire for specific time. This is a strong advantage of reinforced concrete that other construction materials are lacking. Fig.4: Reinforced concrete structure suffered from extreme fire and still stand and has not collapsed
  • 17. NATIONAL BUILDING CODE OF INDIA PART 6 STRUCTURAL DESIGN Section 5 Concrete: 5A Plain and Reinforced Concrete References -