Concrete Calculations
Hydration and Admixtures
Basic Concrete
Prepping, Pouring and Finishing
The Project
100
What is the formula for a rectangle?
(Length) x (Width) x (Height)
100
You mix concrete to a ________?
Ratio
100
What is concrete?
Concrete is a mixture of stone aggregates, sand, Portland cement and water that hardens as it dries
100
A metal or wooden structure that confines the concrete to the desired form until it hardens
Form
100
What is the tool that looks like a wooden 2x4 board called?
A screed
200
What is the formula for a circle?
(3.14 x Radius ^2) x Thickness
200
What is the admixture that traps air bubbles in the concrete to reduce damage during freeze/thaw?
Air Entrainments
200
What are five (5) reasons you might want to use concrete?
-fireproof -insect and rodent proof -decay resistant -highly storm resistant -wear resistant -water proof -strong -attractive -easy to use with little expense -availability -low maintenance -sanitary -easily recycled
200
What is the definition of a "footing" or "footer?"
the concrete base that provides a solid level foundation for stone or brick walls
200

What are the 3 ingredients we added to our concrete mixture.

Sand (fine aggregate)

Stone/Rock (coarse aggregate)

Portland Cement

300
Why do you add 10% to the final number?
To give yourself some wiggle-room
300

Speeds up the Hydration Process.

Chemical admixture- Accelerator

300
What is mortar?
Mortar is a mixture of sand, Portland Cement, water and finishing lime
300
What is a "control joint?"
A control joint is a planned break which permits concrete to expand and contract without cracking.
300
How long does it take for concrete to set?
2 hours
400

You are pouring a rectangle slab, 10ft wide, 10ft long, 6inches thick. What is the exact amount of concrete you need to fill this area. Answer in cubic Yards.

1.85 cubic Yards

400
What is the difference between cement and concrete?
Cement is the glue Concrete is the cake
400
What floats to the top of the water in a silt test?
Organic material
400
What three things can you add to concrete to strengthen it?
Fiberglass, rebar or wire mesh
400
How long does it take for concrete to cure completely?
28 days
500
You have a triangular slab that you need to order concrete for. The dimensions are 8' x 16' x 9". How many cubic yards of concrete do you need to order?
You need to order 2 cubic yards of concrete.
500
What is the process by which the water reacts with the cement, holding the other components together, eventually creating a stone-like mixture?
Hydration
500
Why is the silt test important?
The silt test is key for looking at the sand that will be mixed in with the concrete ingredients. It tells you the type of soil breakdown you have, so that you can determine how much flexibility there will be in the concrete i.e. shrink/swell --> cracks
500
Why do you "tamp" concrete?
Tamping settles the rocks at the bottom of your project. Increases overall strength, stability and aesthetics
500
Why do you need to be careful when adding water to concrete?
If you have too much or too little water, the concrete will crack
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