Conversions, formulas, Advice

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 in 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.

To calculate Cubic Yards Needed, multiply length x width x depth and the divide by 27. All dimensions must be in feet.
Or, for slabs the thickness of a 2x4 form, multiply length by width in feet and divide by 80.

9 to 10 wheelbarrows per yard of concrete

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.
 Age of concrete - in days
 Estimated strength
 3 days
 1140 - 1330 p.s.i
 7 days
 2470 - 2660 p.s.i.
 14 days
 3420 p.s.i.

Coverages – One Cubic Yard Will Cover:
 Sq. Foot Coverage

Concrete Calculator  - This may be a project for winter 2011 !  - If you need help, call us.

Mixing Concrete by Hand:

(3-2-1) 3 Shovels of rock, 2 sand, 1 cement

To make one yard of concrete you need approximately:
 Sidewalk mix
 1800 lbs. of rock
 1200 lbs. coarse sand
 6 bags Type 1A cement
 Footing Mix
 1900 lbs. of rock
 1400 lbs. coarse sand
 5 bags of Type I cement
 Exposed Aggregate Patio Mix
 2200 lbs. of rock
 800 lbs. coarse sand
 6 bags of Type 1A cement
 Grout Mix
  2800 # 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 – see formula below

Stucco Finishing Formula

1 Bag White Cement
2 Bags Silica Sand
1/3 Bag of Lime

 Formulas for making various mortar strengths using a variety of products.
Mortar Type
Cementitious (BAGS)
Cementitious (BAGS)
 1/4 LIME

  • All mixes above are 3 parts sand to one part cementitious.
  • Portland cement has one cubic foot per bag.
  • There are about 7.5 gallons in a cubic foot.

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.

Cold Weather Guidelines
  • 32° 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.

How to Figure a Square:

squaring up, figuring a square, squaring a footing, calculating right angles marshall concrete

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