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1. CONCRE
TE

2. • Concrete is one of the most commonly used
building materials.
• Concrete is a composite material made from
several readily available constituents
(aggregates, sand, cement, water).
• Concrete is a versatile material that can
easily be mixed to meet a variety of special
needs and formed to virtually any shape.

3. The word concrete comes from the Latin word "concretus"
(meaning compact or condensed).
The first major concrete users were the Egyptians in around
2,500 BC and the Romans from 300 BC
• OPUS CAEMENTICIUM
• LAYING BARE ON TOMB
• ROMAN PANTHENON
Opus caementicium laying bare on a tomb near Rome. In
contrast to modern concrete structures, the concrete
walls of Roman buildings were covered, usually with
brick or stone.`
Outer view of the Roman Pantheon, still the largest unreinforced
solid concrete dome to this day.

4. • There are various types of concrete for different applications that are
created by changing the proportions of the main ingredients.
• The mix design depends on the type of structure being built, how the
concrete will be mixed and delivered, and how it will be placed to form the
structure.
Examples include:
• Regular concrete
• Pre-Mixed concrete
• High-strength concrete
• Stamped concrete
• High-Performance concrete
• UHPC (Ultra-High Performance Concrete)
TYPES OF CONCRETE

5. • Self-consolidating concretes
• Vacuum concretes
• Shotcrete
• Cellular concrete
• Roller-compacted concrete
• Glass concrete
• Asphalt concrete
• Rapid strength concrete
• Rubberized concrete
• Polymer concrete
• Geopolymer or Green concrete
• Limecrete
• Gypsum concrete
• Light-Transmitting Concrete

6. EXAMPLES OF CONCRETE TYPE

7. Basic Composition for Main Concretes
• Regular Concrete
– Cement, Aggregate, and water
• Geopolymer (Green concrete)
– Fly Ash and Regular
– Concrete
• High Strength Concrete ~<0.35%
– Silica Fume
– Strong Aggregates
• Ultra High Performance Concrete (UHPC)
– Cement
– Coarse/Fine Aggregate
– Air
– Silica Fume
– Polypropylene Fibers

8. Admixtures and Properties

9. Chemical Admixtures
• Dispersing Agents
–Water Reducers
• Accelerators
• Retarders

10. Water Reducers
• DEFINITION: Water Reducers are used for the
purpose of reducing the quantity of mixing water
required to produce a concrete of given consistency.

11. Accelerators
• DEFINITION: Accelerating admixtures are added to
concrete for the purpose of shortening set time and
accelerating early strength development.

12. Retarders
• DEFINITION: Retarding, and Water-reducing and
retarding admixtures are used to offset acceleration
and unwanted effects of high temperature and keep
concrete workable during placement and
consolidation.

13. Shrinkage Reducing Admixtures
• DEFINITION: Shrinkage Reducing Admixtures are used to
minimize drying shrinkage cracking in concrete .

14. Corrosion Inhibitors
• DEFINITION: Corrosion Inhibitors are used to mitigate
corrosion of reinforcing steel in concrete.

15. ASR Inhibitors
• DEFINITION: ASR Inhibitors (primarily Lithium)
are used to mitigate alkali-silica reactivity in
concrete.

16. Concrete Materials
• Aggregate is the second most influential
ingredient in concrete.
• Aggregate
–Occupies 60-75 % of volume
–Fine Aggregate is typically 35-45 % of
total aggregate
–Mortar (Air, water, cement, fly ash,
sand) is typically 50 - 65 % of total
volume of a mixture

17. Aggregates in Concrete
• Fine: Sand or Crushed Stone (< 5mm)
• Coarse: Gravel or Crushed Stone (5-50 mm)
• Aggregate must be washed in many areas
– Granite & other crushed stone
– Recycled concrete
• All must satisfy ASTM C33

18. Concrete Construction
• Significance of aggregate grading
– smooth grading curve
• (sieve size vs. % passing)
– more voids will lead to more cement.
– undersanded mixes tend to be harsh
– large sizes have less surface area

19. Desired Properties of Fresh
Concrete
Workability
Consistency
Segregation
Bleeding
Setting Time
Unit Weight
Uniformity

20. Concrete - Workability
• cement: too fine of
material
– stickiness
– increased water demand
• water: too much
water
– segregation
– bleeding
• water: too little water
– harshness
– compaction problems
• fly ash: increases flow
– ball bearing effect
– ionic effect
– reduced water demand
• aggregate
– rounded particles flow more
easily
– Too much sand “stickiness”
– Poor gradation - harsh

21. Compressive Strength

22. Concrete Mixture Pre-Design
• Engineer
• Architect
• Contractor
• Concrete Supplier
• Define strength,
congestion and
durability properties
• Defines color, texture,
• Defines workability,
setting time, ..
• Defines aggregates,
cement, fly ash,
admixtures....

23. MIXING OF CONCRETE
 Ready-Mix concrete: In this type ingredients
are introduced into a mixer truck and mixed
during transportation to the site.
• Wet – Water added before transportation
• Dry – Water added at site
 Mixing at the site
• Hand mixed
• Mixer mixed

24. Ready Mix Concrete

25. Hot Weather Concrete
• Rapid hydration  early setting  rapid loss of
workability
• Extra problems due to
– Low humidity
– Wind, excessive evaporation
– Direct sunlight
Solutions
– Windbreaks
– Cooled Concrete Ingredients
– Water ponding (cooling due to evaporation)
– Reflective coatings/coverings

26. Cold Weather Concrete
• Keep concrete temperature above 5 °C to
minimize danger of freezing
Solutions
– Heated enclosures, insulation
– Rely on heat of hydration for larger sections
– Heated ingredients --- concrete hot when placed
– High early strength cement

27. Structure of “un-damaged”
Concrete
Macrostructurem Microstructure

28. VIBRATION OF CONCRETE
 The process of compacting concrete consists
essentially of the elimination of entrapped
air. This can be achieved by:
– Tamping or rodding the concrete
– Use of vibrators

29. Internal Vibration
d
1½ R
Vib
 Internal vibrator: The poker is immersed into concrete to
compact it. The poker is easily removed from point to point.

30. EXTERNAL VIBRATORS
External vibrators: External vibrators clamp direct to the
formwork requiring strong, rigid forms.

31. Advantages
• Ability to be cast
• Economical
• Durable
• Fire resistant
• Energy efficient
• On-site fabrication

32. Disadvantages
• Low tensile strength
• Low ductility
• Volume instability
• Low strength to weight ratio

33. Submitted By
Adesh Gupta
B.Arch