Concrete Technology

Early History of Cement

  • In ancient times, Egyptians mostly used material obtained by burning gypsum.
  • Greeks and romans used the material obtained by burning lime stone.
  • First cement was invented by Joseph Aspidin on 21st October 1824.
  • First cement factory was started at Portland in England.
  • In India, cement was first manufactured in 1904 in Madras by South India Industrial Ltd.
  • Next generation was started by Indian Cement Co. Ltd (1912-13).

 

Manufacturing of Cement

  • Two ways of Manufacturing Cement
  • Dry Process
  • Wet Process (addition of Water)

 

Components of Concrete

  • Cement
  • Aggregates
  • Fine Aggregates
  • Coarse Aggregates
  • Water

 

Aggregates

  • Aggregates give body to the Concrete.
  • They reduce Shrinkage and effect Economy.
  • Aggregates occupy 70-80% of Volume of Concrete.
  • Cement is standard component in concrete.
  • Concrete can be considered as two phases:
  • Paste phase
  • Aggregate phase (contains Aggregates).
  • Shapes of Aggregates
  • Rounded Aggregates- fully water worn
  • Irregular Aggregates- having rounded edges
  • Angular Aggregates- well defined edges
  • Flaky Aggregates- with small thickness, angular

 

Types of Concrete

  • Fresh Concrete
  • Hardened Concrete
  • Special Concrete
  • Light-weight concrete
  • Fiber reinforced concrete
  • Reinforced cement concrete
  • High density concrete
  • Self compacting concrete (SCC).

 

 

Process of Manufacturing of Cement

  • Batching
  • Volume Batching
  • Weigh Batching
  • Mixing
  • Machine Mixing
  • Hand Mixing
  • Transportation
  • Pumps and pipelines
  • Placing
  • Form Work
  • Stripping Time
  • Underwater Concreting
  • Compaction
  • Hand Compaction
  • Internal Vibration
  • Vibratory Rollers
  • Curing
  • Water Curing
  • Steam Curing
  • Electrical Curing
  • Finishing
  • Form work finishes
  • Applied Finish
  • Grinding and Polishing

 

Properties

  • Workability- ease with concrete can be placed and compacted.
  • Factors Affecting
  • Water Content
  • Size of Aggregates
  • Shape of Aggregates
  • Mix Proportions
  • Grading of Aggregates
  • Surface Texture of Aggregates
  • Strength of Concrete
  • w/c ratio
  • Gel space Ratio
  • Elasticity- conc. cube subjected to compression and deformations are measured using gauges.
  • Creep- time dependent part of the strain resulting from stress.
  • Shrinkage- Various aspects of volume changes in concrete due to loss of moisture at different stages due to different reasons.

 

Concrete Mix Design

  • For a concrete technologist, he should have a minimum knowledge about CMD.
  • CMD can be defined as process of selecting suitable ingredients of concrete and determining their relative proportions with object of producing concrete of certain minimum strength and durability as economically as possible.
  • Two methods of designing a concrete mix:
  • American Concrete Institute’s Method
  • Indian Standard’s Method

 

Note

  • Hence cement plays a key role over past 100 years, when human started construction.
  • Cement is the most binding material used by human.
  • Cement has more compression and steel has more tension.
  • No other material is present, which can replace cement.

 

 

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