Post on 31-Mar-2015
LessonLesson
Planning and Placing Planning and Placing ConcreteConcrete
Student Learning ObjectivesStudent Learning Objectives
Describe how to plan the job.Describe how to plan the job. Discuss preparation for the concrete Discuss preparation for the concrete
pour.pour. Explain placing, finishing, and Explain placing, finishing, and
curing concrete.curing concrete.
Terminology Terminology Bag mixBag mix Broom finishBroom finish Bull floatBull float Calcium chlorideCalcium chloride Coarse aggregateCoarse aggregate ConcreteConcrete Concrete dragConcrete drag Concrete edgerConcrete edger Concrete formConcrete form Concrete jointerConcrete jointer CuringCuring
DarbyDarby Earthen formEarthen form Fine aggregateFine aggregate Float finishFloat finish FloatingFloating Form nailsForm nails Gallon mixGallon mix Magnesium or Magnesium or
wooden hand floatwooden hand float Portland cementPortland cement Power trowelPower trowel
Terminology Terminology
Reinforcing barsReinforcing bars Reinforcing wireReinforcing wire Steel hand Steel hand
concrete concrete finishing trowelfinishing trowel
Striking offStriking off Troweled finishTroweled finish
Anticipated Problem:Anticipated Problem:
What do you need to know What do you need to know before pouring concrete?before pouring concrete?
ConcreteConcrete
Is a mixture of coarse Is a mixture of coarse aggregate, fine aggregate, aggregate, fine aggregate, portland cement, and water.portland cement, and water.
ConcreteConcrete
Coarse aggregate: GravelCoarse aggregate: Gravel Fine aggregate: Coarse sandFine aggregate: Coarse sand Portland cement: Cement made Portland cement: Cement made
from burning lime, silica, iron from burning lime, silica, iron oxide, and alumina together. oxide, and alumina together. Gypsum is then added, which acts Gypsum is then added, which acts
as a glue that holds everything as a glue that holds everything togethertogether
Cubic YardsCubic Yards Concrete is figured and sold by Concrete is figured and sold by
the cubic yardthe cubic yard Commonly drop the word “cubic” Commonly drop the word “cubic”
and refer to concrete by the yardand refer to concrete by the yard To calculate the amount needed To calculate the amount needed
convert the length, width, and convert the length, width, and thickness into feet, multiply them thickness into feet, multiply them together, and divide by 27 together, and divide by 27
One cubic yard is 27 cubic feet.One cubic yard is 27 cubic feet.
Cubic YardsCubic Yards
For example a concrete For example a concrete driveway 18 foot × 30 foot driveway 18 foot × 30 foot poured six inches thick would poured six inches thick would be 10 cubic yards (18 × 30 × .5 be 10 cubic yards (18 × 30 × .5 ÷ 27 = 10 cubic yards).÷ 27 = 10 cubic yards).
Selecting MaterialsSelecting Materials
Use quality materialsUse quality materials If soil is present in the sand or If soil is present in the sand or
gravel, the result will be weak gravel, the result will be weak concreteconcrete
Mixing IngredientsMixing Ingredients
Mix in correct proportionsMix in correct proportions Driveways, walks, floors, and Driveways, walks, floors, and
watertight foundations should be watertight foundations should be a six gallon mixa six gallon mix
Foundation walls, footing, and Foundation walls, footing, and mass concrete can be a seven mass concrete can be a seven gallon mix.gallon mix.
Mixing IngredientsMixing Ingredients
Gallon mix: Number of gallons Gallon mix: Number of gallons of water used with a bag of of water used with a bag of cement.cement.
Less water means stronger Less water means stronger concreteconcrete
Mixing IngredientsMixing Ingredients
Bag mix: Number of bags or sacks Bag mix: Number of bags or sacks of cement used per cubic yard of of cement used per cubic yard of concrete.concrete. Example: Six bag mix - Six bags of Example: Six bag mix - Six bags of
cement per cubic yardcement per cubic yard Correct proportions for a six bag mixCorrect proportions for a six bag mix
One part cement to 2¼ parts fine One part cement to 2¼ parts fine aggregate to 3 parts coarse aggregate to 3 parts coarse aggregate.aggregate.
PlanningPlanning
Purchase material to build Purchase material to build concrete forms concrete forms
Assembling tools needed forAssembling tools needed for Digging, Digging, Building and setting forms, Building and setting forms, Installing reinforcement, Installing reinforcement, Pouring concrete, andPouring concrete, and Finishing concreteFinishing concrete
Anticipated Problem:Anticipated Problem:
What do I need to do What do I need to do before the concrete before the concrete
arrives?arrives?
PreparationPreparation
Concrete may be mixed Concrete may be mixed In a wheelbarrow using a shovel In a wheelbarrow using a shovel
or or Shoveled into a small electric or Shoveled into a small electric or
gasoline powered mixergasoline powered mixer Most people purchase ready-Most people purchase ready-
mixed concrete from a local mixed concrete from a local supplier.supplier.
Digging Digging
In many cases the area where In many cases the area where concrete is to be poured or concrete is to be poured or placed must be dug out. placed must be dug out. Example: Driveways and sidewalks Example: Driveways and sidewalks
are generally one inch above the are generally one inch above the ground level when finished.ground level when finished.
Small areas: A shovel may be Small areas: A shovel may be usedused
DiggingDigging
Larger areas need a backhoe, Larger areas need a backhoe, grader blade, or loader bucket grader blade, or loader bucket to speed up the jobto speed up the job
In some cases, like a floor, the In some cases, like a floor, the concrete should be level while concrete should be level while in other situations, like a in other situations, like a driveway, the concrete should driveway, the concrete should slope away from the houseslope away from the house
FormsForms Concrete form: Frame or Concrete form: Frame or
mold that holds new concrete mold that holds new concrete in shape until it has set or in shape until it has set or hardened. hardened.
The forms must be strong The forms must be strong and rigid to prevent sagging, and rigid to prevent sagging, bulging, and spreadingbulging, and spreading
FormsForms Freshly poured concrete exerts Freshly poured concrete exerts
great pressuregreat pressure Earthen form: Trench dug in Earthen form: Trench dug in
the ground with solid walls the ground with solid walls Used for concrete footingUsed for concrete footing
FormsForms When wooden forms are used When wooden forms are used
they must be tight to prevent they must be tight to prevent the escape of the water-the escape of the water-cement paste cement paste A tightly stretched nylon line is A tightly stretched nylon line is
useful to set the forms in a useful to set the forms in a straight line straight line Wooden stakes are used to hold Wooden stakes are used to hold the form boards in positionthe form boards in position
FormsForms
Small jobs: Four foot level on Small jobs: Four foot level on top of the form can be used to top of the form can be used to set the forms level or slopingset the forms level or sloping
Surveying level: Needed to set Surveying level: Needed to set larger jobs. larger jobs.
FormsForms Form nails (or scaffold nails): Form nails (or scaffold nails):
Double-headed nail used to Double-headed nail used to fasten the boards to the fasten the boards to the stakesstakes
Coating forms with used Coating forms with used motor oil or diesel fuel and motor oil or diesel fuel and using form nails make form using form nails make form removal much easierremoval much easier
FillFill
Fill sand or rock should be Fill sand or rock should be added if the area is too deep.added if the area is too deep.
Drag board can be used as fill Drag board can be used as fill is added so that the is added so that the recommended thickness of recommended thickness of concrete will be pouredconcrete will be poured
FillFill
Fill, especially sand, should be Fill, especially sand, should be packed or tamped down so that packed or tamped down so that it is solid.it is solid.
Do not use soil as fill because it Do not use soil as fill because it will settle later leaving a will settle later leaving a void or hole under the void or hole under the concreteconcrete
PlasticPlastic
Place sheet of plastic on top of Place sheet of plastic on top of the fill if the weather is very the fill if the weather is very warm and you would like to warm and you would like to slow down drying and curing slow down drying and curing timetime
Also concrete floors with plastic Also concrete floors with plastic under them are less likely to be under them are less likely to be damp.damp.
Reinforcing Bars and WireReinforcing Bars and Wire
If heavy equipment will drive over If heavy equipment will drive over concrete or freezing and thawing concrete or freezing and thawing will be a problem, concrete should will be a problem, concrete should be reinforcedbe reinforced
Reinforcing bars: Steel bars with Reinforcing bars: Steel bars with ridges that bond with the ridges that bond with the concreteconcrete Commonly seen in the construction Commonly seen in the construction
of highways and bridge decksof highways and bridge decks
Reinforcing Bars and WireReinforcing Bars and Wire
Reinforcing wire: Rolls with wire Reinforcing wire: Rolls with wire rectangles or squares rectangles or squares approximately 6 inches on approximately 6 inches on centercenter Used in lighter construction such Used in lighter construction such
as patios and sidewalks.as patios and sidewalks.
Hot WeatherHot Weather
Consider spraying the area to Consider spraying the area to be poured with water when the be poured with water when the concrete arrivesconcrete arrives
Moisture ContentMoisture Content
Be sure there are no dry Be sure there are no dry clumps and the concrete is clumps and the concrete is thoroughly mixed whether you thoroughly mixed whether you mix or buy ready-mixed.mix or buy ready-mixed.
Water content is very importantWater content is very important
Moisture ContentMoisture Content Extra water will result in weak Extra water will result in weak
concrete but concrete that is concrete but concrete that is too dry is very difficult to pour too dry is very difficult to pour and level off.and level off.
Watch experienced concrete Watch experienced concrete finishers or hire one to help the finishers or hire one to help the first time you pour concrete.first time you pour concrete.
Fiberglass fibersFiberglass fibers
May be added to the concrete May be added to the concrete as it is mixed at the ready-mix as it is mixed at the ready-mix plant as a way to reinforce it.plant as a way to reinforce it.
Calcium ChlorideCalcium Chloride
If concrete is poured in cold If concrete is poured in cold weather calcium chloride is weather calcium chloride is added to prevent the concrete added to prevent the concrete from freezing as it curesfrom freezing as it cures
Building paper or straw can be Building paper or straw can be used to cover the concrete used to cover the concrete after it is finished and while it is after it is finished and while it is curingcuring
Anticipated Problem:Anticipated Problem:
How is concrete placed, How is concrete placed, finished, and cured?finished, and cured?
Placing and Finishing concretePlacing and Finishing concrete
Should not be attempted Should not be attempted without having plenty of laborwithout having plenty of labor
After concrete is mixed the After concrete is mixed the drying and curing process drying and curing process begins you are working against begins you are working against the clockthe clock
Be sure all placing and finishing Be sure all placing and finishing tools are on handtools are on hand
Moving and Spreading ConcreteMoving and Spreading Concrete
Common tools used to move Common tools used to move and spread material:and spread material: Shovels, Shovels, Spades,Spades, Rakes, and Rakes, and Concrete drags Concrete drags
Moving and Spreading ConcreteMoving and Spreading Concrete
Since concrete is so heavy: Move Since concrete is so heavy: Move it downhill with a chuteit downhill with a chute Closer the concrete chute is to Closer the concrete chute is to
where the concrete is needed, the where the concrete is needed, the less work is requiredless work is required
Areas where the chute cannot Areas where the chute cannot reach: use wheelbarrowreach: use wheelbarrow
Concrete should be pushed, pulled, Concrete should be pushed, pulled, or lowered rather than liftedor lowered rather than lifted
Moving and Spreading ConcreteMoving and Spreading Concrete
Concrete drag: Solid blade with Concrete drag: Solid blade with a handle used to push or drag a handle used to push or drag concrete into low spotsconcrete into low spots
Striking off: Using a drag board Striking off: Using a drag board that is usually a 2 ×4 or a 2 ×6 that is usually a 2 ×4 or a 2 ×6 that is used to “saw” back and that is used to “saw” back and forth to level the concrete. forth to level the concrete.
Moving and Spreading ConcreteMoving and Spreading Concrete Work team for placing concrete:Work team for placing concrete:
One person needed at each end of One person needed at each end of the drag board the drag board
Third person with rubber boots and Third person with rubber boots and a concrete drag in middle of the a concrete drag in middle of the concrete make a good team for concrete make a good team for placing concreteplacing concrete
Other workers are needed to Other workers are needed to operate the wheelbarrows and operate the wheelbarrows and shovelsshovels
Moving and Spreading ConcreteMoving and Spreading Concrete
A drag board vibrator can be A drag board vibrator can be clamped to two drag boardsclamped to two drag boards One person with the drag board One person with the drag board
vibrator can do the same work as vibrator can do the same work as two people without it. two people without it.
The concrete should be The concrete should be dragged twice before going on dragged twice before going on to the next step.to the next step.
Moving Fine MaterialMoving Fine Material
To vibrate the fine material To vibrate the fine material next to the form board:next to the form board: Hammer: Used to tap the form Hammer: Used to tap the form
boardsboards Spade: Used to jab up and down Spade: Used to jab up and down
inside the form boardinside the form board
FloatingFloating Pushing the rocks down and Pushing the rocks down and
bringing sand-cement paste to bringing sand-cement paste to the surface and beginning the the surface and beginning the smoothing processsmoothing process
Magnesium or wooden hand Magnesium or wooden hand float: Used to smooth the area float: Used to smooth the area near the edge of the work areanear the edge of the work area
( Picture Courtesy, Interstate Publishers, Inc.)
FloatingFloating
Darby: Two handed float Darby: Two handed float usually 18” long that is also usually 18” long that is also used near the edgeused near the edge
Bull float: 36 or 42 inch float Bull float: 36 or 42 inch float with long round handle used to with long round handle used to reach areas away from the reach areas away from the edgeedge
Rounding the EdgeRounding the Edge
Concrete edger: Used to push Concrete edger: Used to push rocks down near the form rocks down near the form board to round the edge board to round the edge Prevents a chipping or breaking Prevents a chipping or breaking
when the form board is removedwhen the form board is removed
( Picture Courtesy, Interstate Publishers, Inc.)
GroovingGrooving
Concrete jointer: Used to put Concrete jointer: Used to put grooves across concrete areas grooves across concrete areas like sidewalkslike sidewalks
Joints help the appearance and Joints help the appearance and provide relief area provide relief area
Makes cracks in concrete less Makes cracks in concrete less noticeablenoticeable
( Picture Courtesy, Interstate Publishers, Inc.)
Finishing ConcreteFinishing Concrete
Float finish: Leaves rough finish Float finish: Leaves rough finish
acceptable for a livestock feeding acceptable for a livestock feeding floor or footingfloor or footing
Troweled finish: Very smooth Troweled finish: Very smooth finish finish Used for basement and garage Used for basement and garage
floorsfloors( Picture Courtesy, Interstate Publishers, Inc.)
Finishing ConcreteFinishing Concrete
Steel hand concrete finishing Steel hand concrete finishing trowel: Used for small jobs and trowel: Used for small jobs and near the edge on large jobs. near the edge on large jobs.
( Picture Courtesy, Interstate Publishers, Inc.)
Finishing ConcreteFinishing Concrete
Power trowel: Gasoline Power trowel: Gasoline powered trowel with three or powered trowel with three or four blades four blades Used to finish large areasUsed to finish large areas
( Picture Courtesy, Interstate Publishers, Inc.)
Finishing ConcreteFinishing Concrete
Broom finish: Made by using a Broom finish: Made by using a coarse bristle concrete broom coarse bristle concrete broom or floor broom either after or floor broom either after floating or after trowelingfloating or after troweling Often used on driveways and Often used on driveways and
sidewalks for added tractionsidewalks for added traction
CuringCuring
Process of concrete drying and Process of concrete drying and hardening.hardening.
Slower the moisture leaves, the Slower the moisture leaves, the stronger the concrete will stronger the concrete will become. become.
CuringCuring
Helpful Hints:Helpful Hints: Spray concrete with water every Spray concrete with water every
day of the first weekday of the first week Covering the concrete with Covering the concrete with
plastic or a tarp plastic or a tarp Allow the concrete to cure for Allow the concrete to cure for
at least 7 days prior to driving at least 7 days prior to driving vehicles on it.vehicles on it.
Review / SummaryReview / Summary
Describe how to plan the job.Describe how to plan the job. Discuss preparation for the Discuss preparation for the
concrete pour.concrete pour. Explain placing, finishing, and Explain placing, finishing, and
curing concrete.curing concrete.