2. What is concrete
Concrete is a composite material composed
of aggregate bonded together with a fluid cement
which hardens over time.
Ingredients
- Coarse aggregates
- Fine aggregates
- Cement
- Water
- Admixtures
8. Mixing
• A concrete mixer is a device that homogeneously
combines cement, aggregate such as sand or
gravel, and water to form concrete.
• Type of mixtures
1. Pan type
2.Drum type
- Tilting
- Non tilting
- Reversing
11. History of concrete
• The time period during which concrete was first
invented depends on how one interprets the term
“concrete.” Ancient materials were crude cements
made by crushing and burning gypsum or limestone.
Lime also refers to crushed, burned limestone. When
sand and water were added to these cements, they
became mortar, which was a plaster-like material used
to adhere stones to each other. Over thousands of
years, these materials were improved upon, combined
with other materials and, ultimately, morphed into
modern concrete.
12.
13. • Today’s concrete is made using Portland cement,
coarse and fine aggregates of stone and sand, and
water. Admixtures are chemicals added to the
concrete mix to control its setting properties and are
used primarily when placing concrete during
environmental extremes, such as high or low
temperatures, windy conditions, etc.
17. Workability
Effort required to manipulate a concrete mixture
with a minimum of segregation.
• Factors affecting
1. w/c ratio
2. Size of aggregates
3. Shape of aggregates
4. Surface texture of aggregates
5. w/c ratio
18. Test for determination of workability
1. Slump test
2. Compacting factor test
3. Vee Bee test
4. Flow test
20. Segregation
Segregation is when the coarese and fine
aggregate , and cement paste, become
seperated .
Segregation may happen when the concrete is
mixed , transported, placed or compacted.