AQE 1: BTECH1

• Concrete


  A composite material, consisting mainly of Portland cement, water and aggregate (gravel, sand or rock).
• 41% - Gravel

  26% - Sand

  16% - Water

  11% - Cement

  6% - Air


  Typical Concrete Mix (by volume)
• Cement


  The binding material in a cement concrete mixture.
• 1. makes the concrete impermeable

  2. provides strength to concrete on setting and hardening

  3. binds the aggregate into a solid mass


  Functions of Cement
• Ordinary Portland Cement (OPC)


  A type of cement that is manufactured and used worldwide.
• Mortar


  For joining masonry
• Plaster


  To give a perfect finish to the walls
• Rapid Hardening Cement


  A type of cement made when finely grounded C3S is displayed in OPC with higher concrete.

  
  

  Commonly used in rapid constructions.
• Extra Rapid Hardening Cement


  A type of cement that gains strength quicker and is obtained by adding calcium chloride to RHC.

  
  

  Commonly used in cold weathering conditions.
• Portland Pozzolana Cement (PPC)


  A type of cement that grinds pozzolanic clinker with portland cement. Has a high resistance to different chemical assaults on concrete.

  
  

  Widely used in marine structures, bridges, piers, dams, etc.
• 25%


  How many percent is Extra Rapid hardening cement faster than RHC?
• Low Heat Cement


  A type of cement that is used in mass concrete construction.

  
  

  Less reactive and the initial setting time is greater than OPC.
• Sulfates Resisting Cement


  A type of cement that is manufactured to resist sulfate attack in concrete.

  
  

  Can be used in concrete surfaces subjected to alternate wetting and drying like bridge piers.
• Quick Setting Cement


  A type of cement that the proportion of gypsum is reduced.

  
  

  Used for constructions like underwater structures.
• Blast Furnace Slag Cement


  A type of cement used for constructions where economic considerations are important.
• High Alumina Cement


  A type of cement that is commonly used in constructions that are subject to high temperatures.
• White Cement


  A type of cement that is manufactured by using raw materials that are free from iron and oxide.

  
  

  Needs to have lime and clay in a higher proportion.
• 1. Fine Aggregate

  2. Coarse Aggregate


  Two types of Aggregate?
• less than 4.75mm


  Particle size of fine aggregate
• more than 4.75mm


  Particle size of coarse aggregate
• Fine Aggregate (Sand)


  Consists of small angular or rounded grains of silica.

  
  

  Reduces shrinkage and cracking of concrete, fills voids existing, hardens cement by allowing water through its voids.
• Coarse Aggregate


  Makes solid and hard mass of concrete with cement and sand.

  
  

  Reduces cost of concrete and increases crushing size.
• Water


  Is used in concrete and plays and important part in the mixing, laying compacting setting and hardening of concrete.
• Water


  Lubricant for aggregate and makes the concrete workable
• Concrete Admixtures


  Are added to change the properties of concrete to make in function.
• Concrete Mix Design Procedure


  The process of selecting proportions of cement, water, aggregates, etc. to produce an economical concrete mix.
• Batching


  Is measuring and introducing the concrete ingredients into the mixer.
• Batching by volume


  This method is generally adopted for small jobs.

  
  

  Gauge boxes are used for measuring the aggregates.
• Batching by weight


  Batching that is more accurate and leads to more uniform proportioning
• 1. Manual

  2. Semi - automatic

  3. Fully - automatic


  3 general categories of batching by weight
• 1.5 meter cube - 9 meter cube


  Capacity of concrete mixers
• Dry Mixing


  Occurs during loading but before water is introduced.
• Wet Mixing


  Mixing after or while water is being introduced.
• The Mixing Period


  defined as the time between the loading of all constituents and the beginning of concrete discharge.
• The discharge


  should be arranged so that it increases productivity.
• Batch Plant or Batching Plant


  is a device/plant that combines various ingredients to form concrete.
• Ready Mixed Concrete


  is a technique of production of concrete in massive quantities away from the actual site of placing
• 1. Cohesiveness

  2. Workability

  3. Strength

  4. Durability

  5. Modulus of Elasticity

  6. Volume Change


  6 Properties of Concrete
• 1. Slump Test

  2. Compaction Factor Test

  3. Vee-bee Consistometer Test


  Workability may be determined by the 3 methods:
• Consistency


  described as the "ease of flow" of the concrete.