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Fun Concrete Facts
This page has many formulas and short cuts to help you plan a concrete project, large or small. Plus some wisdom from old-timers, and some things that could make you look really smart if you know them. They are "fun facts" - fun things to know, how to do - kind of a mini-reference page. If you need a conversion or a little fact that would be handy to have listed here, contact Fish at Marshall and we'll add it.

1 Ton = 2000 lbs.
1 Cubic Yard of sand weighs 2800 lbs.
1 Cubic Yard of rock weighs 3000 lbs.
1 Yard of concrete weighs about 4000 lbs.
9 to 10 wheelbarrows per yard of concrete

Cubic Yards Calculation
Multiply length x width x depth and the divide by 27. All dimensions must be in feet.

Slab Thickness Calculation
Multiply length by width in feet and divide by 80.
Concrete Strength

Concrete gains strength over time. As long as conditions for hydration exist continuously, strength gain continues indefinitely, though at a very slow pace. It is the early end of strength gain that is of greater interest. Typically, concrete gains 95% of its strength in 28 days. It gains 30-35% of its 28 day strength in 3 days, 65-70 percent in 7 days and 90% in 14 days. The table below shows the expected strength gains. Obviously job site conditions and other variables can change these numbers, but this provides a general guideline.  Estimated strength of 4000 p.s.i. concrete before 28 days:
3 days of aged concrete
1140 - 1330 p.s.i. estimated strength

7 days of aged concrete
2470 - 2660 p.s.i estimated strength

14 days of aged concrete
3420 p.s.i
One Cubic Yard Will Cover:
2" deep - 160 square foot coverage
3" deep - 108 square foot coverage
4" deep - 80 square foot coverage
5" deep - 65 square foot coverage
6" deep -54 square foot coverage
8" deep -40 square foot coverage
12" deep - 27 square foot coverage
Mixing Concrete by Hand
3 Shovels of Rock
2 Shovels of Sand
1 Shovel of Cement
To Make One Yard of Concrete You Need Approximately:
Sidewalk Mix
1800 lbs. of rock
1200 lbs. of coarse sane
6 bags Type 1A cement

Footing Mix
1900 lbs. of rock
1400 lbs. or coarse sand
5 bags of Type I cement

Exposed Aggregate Patio Mix
2200 lbs. of rock
800 lbs. of coarse sand
6 bags of Type 1A cement

Grout Mix
2800 lbs. of coarse sand
8 bags of Type 1A cement

Stucco -- typically 3 coats
1st coat - Scratch coat
Use Type M or S mortar with sand

2nd coat - Brown coat
Use Type M or S mortar with sand

3rd coat - Finish Coat
White Portland  (1 bag white cement, 2 bags of silica sand and 1/3 bag of lime)

Formula for Making Various Mortar Strengths Using a Variety of Products
Mortar Type:  Type "M"
Cementitious (bags):  1 Portland
Cementitious (bags):  1 Type "N" Masonry Cement
Sand (5 gallon buckets):  9
Mortar Type:  Type "M"
Cementitious (bags):  1 Portland
Cementitious (bags):  1/4 Lime
Sand (5 gallon buckets):  5.5

Mortar Type:  Type "M"
Cementitious (bags):  1 Type "M" Masonry Cement
Sand (5 gallon buckets):  4.5

Mortar Type:  Type "S"
Cementitious (bags):  1/2 Bag Portland
Cementitious (bags):  1 bag Type "N" Masonry Cement
Sand (5 gallon buckets):  6.75

Mortar Type:  Type "S"
Cementitious (bags):  1 Type "S" Masonry Cement
CSand (5 gallon buckets):  4.5

Mortar Type:  Type "S"
Cementitious (bags):  1 Portland
Cementitious (bags):  1/2 Bag Lime
Sand (5 gallon buckets):  6.75

Mortar Type:  Type "N"
Cementitious (bags):  Type "N" Masonry Cement
Sand (5 gallon buckets):  4.5

Mortar Type:  Type "N"
Cementitious (bags):  1 Portland
Cementitious (bags):  1 Lime
Sand (5 gallon buckets):  9
Cleaning Concrete Surfaces

Ultra Dawn dish soap, full strength, scrub, leave it for 10-15 minutes, rinse thoroughly. If this doesn't do it ... make a poultice of Dawn (full strength) and either ordinary Talc or Fullers Earth to about the consistency of wet tooth paste. Spread on the oil stained area, cover with plastic, leave overnight. Next day get it good and wet, scrub, rinse thoroughly.

Castrol puts out a product called Super Clean. Soak the area with it, cover for about 15 minutes with plastic, scrub & rinse thoroughly. If this doesn't do it ... wet the spot with the cleaner again, put kitty litter on top of it, wet the kitty litter too, place plastic over it, leave for a couple of hours, remove the plastic and let the kitty litter dry out, drawing/pulling the oil up into it as it does so. Wash with Dawn, scrub, rinse.

Make a poultice out of dry/powdered laundry detergent (toothpaste consistency) and water, apply, cover with plastic, leave overnight, scrub rinse thoroughly.

Simply Green can also be used to make a poultice using either Talc or Fullers Earth (toothpaste consistency), cover with plastic for a couple of hours, scrub, rinse.

How to Figure a Square

Figuring a square is an important skill in the construction field.  Many contractors use squaring up manuals to complete the task.  But, with modern, inexpensive calculators, figuring out your squares with a calculator is easy to do.  The calculation is based on a geometric principle discovered centuries ago by a mathematician named Pythagorus.  Pythagorus figured out that you can calculate the length of the hypotenuse of any right (or 90 degree) triangle by using the following formula:

hypotenuse of a right triangle
A2 + B2 = C2, where C is the hypotenuse, and A and B are adjacent to the right angle.

So, for a angle with two sides, one 30' and another 40', the formula works like this:
30 x 30 + 40 x 40 = C2, run the calculations and you get:
900 + 1600 = 2500  = C2.   √C = (Square Root of 2500) = 50

Of course, most squares aren't this easy.  Let's take another example.  Two sides A and B of 24 and 26 feet.  The formula becomes 576 + 576 = 1252.  Square Root of 1252 is 35.383 feet.  Of course, since we use the English system instead of Metric, you will need to convert everything on the right side of the decimal point into inches and eighths.  So take .383 feet, multiply it by 12 and you get 4.596 inches.  To convert .596 inches into eighths, multiply it by 8, and you get 4.77, so you round that up to the nearest eighth of an inch, so it is 5/8 inch.  So, the answer is 35' 4 and 5/8".

With a calculator and remembering the decimal to inch and eighths conversion, you'll never need a square book again.

Cold Weather Guidelines32° to 40° F Heat water to produce mortar at or above 40° F.
  • 0° to 32° F Heat water and sand to produce mortar at 40° to 120° F and keep above freezing until used.
  • Below 0° F Masonry work generally should not be attempted

Premix Products
  • Each 80-lb. bag of concrete or sand mix covers .667 cubic foot
  • 40 bags are need for one cubic yard
  • 1 bag of mortar will lay about 12-15 blocks

Core Fills
  • 1 yard of grout will fill:
  • 100 8x8x16 common block
  • 60 12x8x16 common block
1 core, 12 courses high requires 2.5 cubic feet – so 1 yard of grout will fill 10 cores on a 12 course basement wall.

  • Footings must be at least 42" below grade in Metro area.
  • 12" block require a minimum of 8" x 20" footings – 24 feet of footing per yard.
  • 8" block require a minimum of 8" x 16" footings – 30 feet of footing per yard of concrete.


Square feet divided by 80 gives yardage required for 4" thick slabs. Add at least 10% for orders less than five yards.

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