Concrete in brief


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Concrete in brief

  1. 1. Properties of concrete Workability Segregation Bleeding  Strength  Elasticity  Shrinkage  Creep  Durability
  2. 2. Workability Easily mixed, handled, transported, placed in position and compacted Segregation Separation of constituent materials of concrete Creates larger voids and reduces the durability and strength Bleeding Water from concrete comes out of the surface Produces pores in concrete and reduces strength.
  3. 3. Strength Compressive strength, tensile strength, flexural strength
  4. 4. Flexural testing
  5. 5. Elasticity Concrete not an elastic material Stress in concrete a strains in initial stages Influenced by elastic properties of aggregate, mix proportion, age of concrete, type of cement
  6. 6. Shrinkage Change in volume of concrete due to loss of moisture at different stages Affects strength and durability Leads to the formation of cracks Depends on constituents of concrete, size of member, amount of water present in concrete and environmental conditions
  7. 7. Creep Gradual increase in strain without increase in stress, with time Depends on stress in concrete, age at loading and duration of loading
  8. 8. Durability Ability to resist weathering action, chemical attack, abrasion or any other process of deterioraton Factors affecting are environment, cover to embedded steel, type and quality of constituent materials, cement content and water cement ratio, workmanship to obtain full compaction, efficient curing and shape and size of member
  9. 9. Types of concrete Reinforced cement concrete Fibre reinforced concrete Ferrocement Light weight concrete Ready-mixed concrete Shotcrete Polymer concrete
  10. 10. Fibre reinforced concrete Fibres- natural materials like asbestos and cellulose, or manufactured products such as glass, steel carbon and polymer Road pavements, industrial flooring, bridge decks, canal linings, explosive resistant structures etc.
  11. 11. Ferrocement Closely spaced, multiple layers of mesh or fine rods completely surrounded by cement mortar. Casting overhead water tanks, gober gas plants, boat building, manhole covers, roofing units, pressure pipes etc.
  12. 12. Light weight concrete Density lower than ordinary concrete Light weight aggregates or introducing gas or air bubbles long span bridges, fire protection for steel work in tall buildings, filling for floor and roof slab
  13. 13. Shotcrete Shotcrete is a process where concrete is projected or "shot" under pressure using a feeder or "gun" onto a surface to form structural shapes including walls, floors, and roofs. Shotcrete has high strength, durability, low permeability, excellent bond and limitless shape possibilities.
  14. 14. • Polymer concrete is part of group of concretes that use polymers to supplement or replace cement as a binder. The types include polymer- impregnated concrete, polymer concrete, and polymer-Portland-cement concrete.
  15. 15. Ready-mixed concrete
  16. 16. Advantages of cement concrete Readily moulded High compressive strength Free from corrosion Hardens with age Resists abrasion Impermeable Provides good bond Control properties of concrete
  17. 17. Advantages of cement concrete Mechanise completely its preparation Adequate plasticity for mechanical working More economical than steel Compatible with other materials like steel Disadvantages Low tensile strength Self weight high Not suitable for speedy construction-curing
  18. 18. Admixtures and additives Accelators Admixtures which accelerate hardening/ development of early strength. Sodium carbonate,aluminiium chloride, potassium carbonate, sodium aluminate etc Set retarders Admixtures which delay the setting of concrete Common sugar, carbohydrate derivative
  19. 19. Water reducers(plasticizers) To achieve higher strength by decreasing water cement ratio To achieve same workability by decreasing cement content To increase the workability