Concrete is one of the most durable, economical and versatile building materials, used on everything from driveways to lighthouses. Randy Williams of QuikreteB) offers a lesson in the basics of making and using concrete. Concrete is composed of a binding medium (usually Portland cement), aggregate and water (figure A). Portland cement is a mixture of minerals fired in a kiln, combined with gypsum ground fine (figure B). It's sold in 1-cubic-foot bags weighing 94 pounds each. A combination of fine and coarse aggregate makes up 60 percent to 75 percent of a given volume of concrete (figure C). Fine aggregate is sand that will pass through a 1/4" screen. Coarse aggregate consists of gravel and crushed stone between 1/4" and 1 1/2" in diameter. To determine how much concrete is needed to fill a rectangular or square surface, use either of the following formulas: - [Width in feet x length in feet x thickness in inches] divided by 324 equals cubic yards of concrete needed
- [Width in feet x length in feet x thickness in inches] divided by 12 equals cubic feet of concrete needed
When working with concrete, always wear a mask or respirator and gloves for protection. Mix the concrete in a large bucket or wheelbarrow until you get a mass of uniform color without brown or gray streaks (figure D). For surfaces that will be exposed to moderate weather and wear, a mix of 1 part cement, 2 1/2 parts sand and 3 parts gravel is recommended. For projects not subject to wear and weather, use 1 part cement, 2 3/4 parts sand and 4 parts gravel. Use a metal trowel to spread the concrete, eliminating all air pockets (figure E).
RESOURCES :
QUIKRETE® Information
To obtain expert advice on Do-It-Yourself concrete projects, to inquire about specific QUIKRETE® products, to find out where to buy the products or to order product literature, please call 1-800-282-5828.
To easily calculate how much concrete you'll need for a job, click here.
The QUIKRETE® Companies
Website: www.quikrete.com
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