Se ha denunciado esta presentación.
Utilizamos tu perfil de LinkedIn y tus datos de actividad para personalizar los anuncios y mostrarte publicidad más relevante. Puedes cambiar tus preferencias de publicidad en cualquier momento.
CONCRET
E The Man Made Stone
Introduction..
• Concrete is a composite material composed mainly of
water, aggregate, and cement.
• The word concrete com...
Colloseum, Greece
Pantheon, Rome
Petronas twin Tower Burj Khalifa
Types of Concrete
• Light weight concrete: used for load bearing external
walls for building. They are also used for tempo...
Constituents..
Constituents..
•Mixture of aggregate
•paste 30 to 40%
• portland cement 7% to 15% by Vol.
• water 14% to 21% by Vol.
•Aggr...
Portland Cement
• Dry powder of very fine particles
• forms a paste when mixed with water
• chemical reaction-Hydration
• ...
Water
• needed for two purposes:
• chemical reaction with cement
• workability
• only 1/3 of the water is needed for chemi...
Aggregates
• cheap fillers
• hard material
• provide for volume stability
• reduce volume changes
• provide abrasion resis...
Admixtures
• chemical
• set retarders
• set accelerators
• water reducing
• air entraining
• mineral
• fly ash
• silica fu...
Fresh Concrete
Fresh concrete is that stage of
concrete in which concrete can
be moulded and it is in plastic
state.
Properties of fresh concrete
•Setting
•Workability
•Bleeding
•Segregation
•Hydration
•Air Entrainment
Setting Of Concrete
The hardening of concrete before
its hydration is known as setting of
concrete
Factors affecting setting
• Water Cement ratio
• Suitable Temperature
• Cement content
• Type of Cement
• Fineness of Ceme...
Water-cement Ratio
The water–cement ratio is the ratio of the weight of water to
the weight of cement used in a concrete m...
Workability
• Workability is often referred to as the ease with which a
concrete can be transported, placed and consolidat...
Factors affecting concrete workability
• Water-Cement ratio
• Amount and type of Aggregate
• Amount and type of Cement
• W...
Test for Workability
Slump Test can be used to find out the
workability of concrete
Apparatus for Slump test
• Cylinders
• Small scoop
• Bullet-nosed rod (600 mm
x 16 mm)
• Steel float
• Steel plate 8”
4”
1...
Slump Test
slump cone
rod
concrete
Procedure
• Clean the cylinder mould and coat the inside lightly with form
oil, then place on a clean, level and firm surf...
Procedure
• Level off the top with the steel float and clean any
concrete from around the mould.
• Cap, clearly tag the cy...
Slump test results
• stiff 0-2”
• massive sections, little reinforcement
• use vibration
• medium 2-5”
• columns, beams, r...
Factors affecting slump
• water cement ratio
• w/c = weight of water / weight of cement
example:
weight of water mixed at ...
water cement ratio
if you add 10 gallons of water per cubic yard at job site, then:
extra water
10 gallons/cubic yard * (3...
Factors affecting slump-
paste content
• constant water cement ratio
• increase paste content
• increase slump
• NO GOOD
•...
Factors Affecting Slump-
Water Content
• Add water at the constant cement content, w/c increases,
slump increases.
• Add w...
Factors affecting slump-paste content
Low paste content
Harsh mix
High paste content
Rich mix
ball bearing effect-start
starting height
ball bearing effect-end
Factors affecting slump
• Aggregates
• grading the larger the particle size, the higher the slump for
a given paste content
effect of aggregate size
1”
1”
1”
Consider a single aggregate the size of 1”x1”x1”
Break it up further
Compute the surface area
0.5 in
0.25 in
surface area = 0.25*0.25*6*8*8=24
Larger particles, less surface area,
thicker coating, easy sliding of
particles
Smaller particles, more surface area,
thinner coating, interlocking of
particles
Angularity and surface
texture of aggregates
angular and rough
aggregate
smooth aggregate
river gravel
Temperature
fresh concrete
aggregates paste
Bleeding
• Bleeding is a form of segregation
where some of the water in the
concrete tends to rise to the surface
of the f...
Bleeding
Prevention of Bleeding in concrete
• Bleeding can be reduced by proper proportioning and
uniform and complete mixing.
• Ai...
Curing
• The time needed for the
chemical reaction of cement
with water results in greater
bonding and makes stronger.
• c...
Curing tips
• ample water
• do not let it dry
• dry concrete = dead concrete, all reactions stop
• can not revitalize conc...
Temperature effects on
curing
• The higher the temperature the faster the curing
• best temperature is room temperature
• ...
Temperature effects on
curing
• real high temperatures above 120 F can cause
serious damage since cement may set too fast....
Advantage Of Concrete
• Concrete is economical when ingredients are readily
available.
• Concrete’s long life and relative...
Advantages Of Concrete
• Building of the molds and casting can occur on the work-
site which reduces cost.
• Concrete is a...
Disadvantage
• Concrete has a relatively low tensile strength. In order to
over this, steel is reinforced
• low ductility
...
CONCRETE
Próxima SlideShare
Cargando en…5
×

CONCRETE

1.018 visualizaciones

Publicado el

CONCRETE TEST PROPERTY

Publicado en: Ingeniería
  • Sé el primero en comentar

CONCRETE

  1. 1. CONCRET E The Man Made Stone
  2. 2. Introduction.. • Concrete is a composite material composed mainly of water, aggregate, and cement. • The word concrete comes from the Latin word "concretus" meaning compact or condensed • It is believed that romans were the one who introduced concrete and used extensively from 300 BC to 476 AD. • After the Roman Empire collapsed, use of concrete became rare until the technology was re-pioneered in the mid-18th century
  3. 3. Colloseum, Greece
  4. 4. Pantheon, Rome
  5. 5. Petronas twin Tower Burj Khalifa
  6. 6. Types of Concrete • Light weight concrete: used for load bearing external walls for building. They are also used for temporary structures because of low initial cost and can be reused as aggregate • High density concrete : They are mainly used in the construction of radiation shields (medical or nuclear) • Mass concrete : used in building dams, foundation etc • Ready mix Concrete : Ready Mixed Concrete is manufactured under computer-controlled operations
  7. 7. Constituents..
  8. 8. Constituents.. •Mixture of aggregate •paste 30 to 40% • portland cement 7% to 15% by Vol. • water 14% to 21% by Vol. •Aggregates 60% to 70% • coarse aggregates • Fine aggregates •Admixtures
  9. 9. Portland Cement • Dry powder of very fine particles • forms a paste when mixed with water • chemical reaction-Hydration • glue • paste coats all the aggregates together • hardens and forms a solid mass
  10. 10. Water • needed for two purposes: • chemical reaction with cement • workability • only 1/3 of the water is needed for chemical reaction • extra water remains in pores and holes • results in porosity • Good for preventing plastic shrinkage cracking and workability • Bad for permeability, strength, durability.
  11. 11. Aggregates • cheap fillers • hard material • provide for volume stability • reduce volume changes • provide abrasion resistance
  12. 12. Admixtures • chemical • set retarders • set accelerators • water reducing • air entraining • mineral • fly ash • silica fume • slags
  13. 13. Fresh Concrete Fresh concrete is that stage of concrete in which concrete can be moulded and it is in plastic state.
  14. 14. Properties of fresh concrete •Setting •Workability •Bleeding •Segregation •Hydration •Air Entrainment
  15. 15. Setting Of Concrete The hardening of concrete before its hydration is known as setting of concrete
  16. 16. Factors affecting setting • Water Cement ratio • Suitable Temperature • Cement content • Type of Cement • Fineness of Cement • Relative Humidity • Admixtures • Type and amount of Aggregate
  17. 17. Water-cement Ratio The water–cement ratio is the ratio of the weight of water to the weight of cement used in a concrete mix and has an important influence on the quality of concrete produced
  18. 18. Workability • Workability is often referred to as the ease with which a concrete can be transported, placed and consolidated without excessive bleeding or segregation
  19. 19. Factors affecting concrete workability • Water-Cement ratio • Amount and type of Aggregate • Amount and type of Cement • Weather conditions • Temperature • Wind • Chemical Admixtures • Sand to Aggregate ratio
  20. 20. Test for Workability Slump Test can be used to find out the workability of concrete
  21. 21. Apparatus for Slump test • Cylinders • Small scoop • Bullet-nosed rod (600 mm x 16 mm) • Steel float • Steel plate 8” 4” 12”
  22. 22. Slump Test slump cone rod concrete
  23. 23. Procedure • Clean the cylinder mould and coat the inside lightly with form oil, then place on a clean, level and firm surface, ie the steel plate. Collect a sample. • Fill 1/2 the volume of the mould with concrete then compact by rodding 25 times. Cylinders may also be compacted by vibrating using a vibrating table. • Fill the cone to overflowing and rod 25 times into the top of the first layer, then top up the mould till overflowing.
  24. 24. Procedure • Level off the top with the steel float and clean any concrete from around the mould. • Cap, clearly tag the cylinder and put it in a cool dry place to set for at least 24 hours. • After the mould is removed the cylinder is sent to the laboratory where it is cured and crushed to test compressive strength
  25. 25. Slump test results • stiff 0-2” • massive sections, little reinforcement • use vibration • medium 2-5” • columns, beams, retaining walls • Fluid 5-7” • heavily reinforced section, flowable concrete
  26. 26. Factors affecting slump • water cement ratio • w/c = weight of water / weight of cement example: weight of water mixed at the plant 292 lbs. weight of cement 685 lbs./cu. yard w/c = 292/685 = 0.43
  27. 27. water cement ratio if you add 10 gallons of water per cubic yard at job site, then: extra water 10 gallons/cubic yard * (3.8 liters/gallon) * (2.2 lbs./kg) *( 1kg/liter) = 83.77 lbs. total water 282 + 83.77 = 365.77 new w/c = 365.77 / 685 = 0.534 >> 0.43
  28. 28. Factors affecting slump- paste content • constant water cement ratio • increase paste content • increase slump • NO GOOD • constant cement content • increase water content • increase slump • NO GOOD
  29. 29. Factors Affecting Slump- Water Content • Add water at the constant cement content, w/c increases, slump increases. • Add water at a constant water cement ratio, have to increase cement as well, slump increases.
  30. 30. Factors affecting slump-paste content Low paste content Harsh mix High paste content Rich mix
  31. 31. ball bearing effect-start starting height
  32. 32. ball bearing effect-end
  33. 33. Factors affecting slump • Aggregates • grading the larger the particle size, the higher the slump for a given paste content
  34. 34. effect of aggregate size 1” 1” 1” Consider a single aggregate the size of 1”x1”x1”
  35. 35. Break it up further
  36. 36. Compute the surface area 0.5 in 0.25 in surface area = 0.25*0.25*6*8*8=24
  37. 37. Larger particles, less surface area, thicker coating, easy sliding of particles
  38. 38. Smaller particles, more surface area, thinner coating, interlocking of particles
  39. 39. Angularity and surface texture of aggregates angular and rough aggregate smooth aggregate river gravel
  40. 40. Temperature fresh concrete aggregates paste
  41. 41. Bleeding • Bleeding is a form of segregation where some of the water in the concrete tends to rise to the surface of the freshly placed material.
  42. 42. Bleeding
  43. 43. Prevention of Bleeding in concrete • Bleeding can be reduced by proper proportioning and uniform and complete mixing. • Air-entraining agent is very effective in reducing the bleeding. • Bleeding can be reduced by the use of finer cement or cement with low alkali content. Rich mixes are less susceptible to bleeding than lean mixes.
  44. 44. Curing • The time needed for the chemical reaction of cement with water results in greater bonding and makes stronger. • concrete after 14 days of curing has completed only 40% of its potential. 70 % at 28 days
  45. 45. Curing tips • ample water • do not let it dry • dry concrete = dead concrete, all reactions stop • can not revitalize concrete after it dries • keep temperature at a moderate level • concrete with flyash requires longer curing
  46. 46. Temperature effects on curing • The higher the temperature the faster the curing • best temperature is room temperature • strongest concrete is made at temperature around 40 F.(not practical) • If concrete freezes during the first 24 hrs., it may never be able to attain its original properties.
  47. 47. Temperature effects on curing • real high temperatures above 120 F can cause serious damage since cement may set too fast. • accelerated curing procedures produce strong concrete, but durability might suffer. • autoclave curing.
  48. 48. Advantage Of Concrete • Concrete is economical when ingredients are readily available. • Concrete’s long life and relatively low maintenance requirements increase its economic benefits. • It is not as likely to rot, corrode, or decay as other building materials. • Concrete has the ability to be molded or cast into almost any desired shape.
  49. 49. Advantages Of Concrete • Building of the molds and casting can occur on the work- site which reduces cost. • Concrete is a non-combustible material which makes it fire-safe and able to withstand high temperatures. • It is resistant to wind, water, rodents, and insects. Hence, concrete is often used for storm shelters
  50. 50. Disadvantage • Concrete has a relatively low tensile strength. In order to over this, steel is reinforced • low ductility • low strength-to-weight ratio, and • Concrete is susceptible to cracking.

×