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Concrete Calculations
Hydration and Admixtures
Basic Concrete
Prepping, Pouring and Finishing
Projects
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

How to you convert cubic feet to cubic yards?

1 cubic yard= 27 cubic feet

Divide your cubic feet by 27 to get cubic yards.

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 characteristics of a good workable mix?

- All aggregates are clean 

- No dry powder is present 

- No lumps

-Uniform in color

-Every part of aggregate is covered with cement paste

300
Why do you add 10% to the final number?
To give yourself some wiggle-room
300
Slows the hydration process down
Chemical admixture- retarders
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?

about 24 hours

400

What are the steps necessary to solving concrete calculation problems?

1. Convert everything to feet by dividing by 12 

2. Solve in feet (multiply all items to find cubic feet) 

3. Convert to cubic yards by dividing by 27 

4. Add 10% 

5. Round up for an order number

400

What is the name of the Chemical Admixtures that speed up a chemical process? 

Accelerators 

CaCl & NaCl for Hydration 

400

What sinks to the top of the water in a silt test?

Sand

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 4 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