How to Use Prepackaged Concrete Mix

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For very small concrete projects like sidewalk or driveway repairs, bags of premixed concrete can be a money saving alternative to buying Ready-Mixed bulk concrete. This product, available in bags of dry blended material can be purchased in home improvement and building supply stores in many areas.

Steps

Figure out how much premixed concrete you will need for your project. Multiply the length times the width times the depth of the space you need to fill. This will tell you give a cubic size, or volume, of concrete that you need. Next, divide the volume (in cubic feet, meters, etc.) by the package yield of the material you are using. Typically, premixed concrete comes in 20, 40, and 80 pound bags, with the 80 pound bag yielding about 4/5 of a cubic foot of concrete.
Prepare any forms you will need to hold the concrete, and grade and compact the soil or sub grade material. Place any reinforcing steel, and generally speaking, be ready for your concrete.
Purchase the premixed product you have chosen to use. Here are a few examples of different mixtures commonly available:
- 3000 PSI (pounds per square inch) compressive strength, gravel, sand, and Portland cement mixture. This is a basic, inexpensive concrete suitable for most repairs, as well as for setting posts and poles.
- 4000 PSI mixture is for repairing or building structural concrete like sidewalks or driveways, where extra strength will increase the durability of the finished surface.
- 5000 PSI quick-setting concrete is a very strong mixture with a higher ratio of Portland cement to fine and coarse aggregates, typically used where quick-setting is desirable and higher strength may be needed.
- Sand mix contains no gravel or stone (coarse aggregate) and is used for grouting or topping, where a smoother surface is desired.
- Other mixes include premixed mortars, non-metallic non-shrink grouts and high-strength early (high early) concrete. These are specialty mixes for specific purposes not covered in this article.
Gather the materials you will need to complete your project. See "Things You'll Need" below for a complete list, but these will include your dry concrete mix, clean water, a shovel, and a container for mixing.
Open a bag of your concrete mix and pour it into your mixing container. Wheelbarrows (as in the pictures) are ideal for mixing small quantities of concrete. Avoid spilling the dry material on finished surfaces or lawn grasses, and keep upwind if possible to avoid breathing dust from this product.
Make a small depression or hole in the dry material in the center of the container, using a shovel or mixing hoe. This will act as a reservoir for the water you add. Pour one gallon of water for each 60 pounds of dry mix into the depression. Don't worry about overflow or splashing, because all the container's contents must be mixed completely before the concrete is used.
Stir the material and water, using a shovel or mixing hoe, so all the material is wetted. Add additional water until the concrete is as plastic as you want it to be for your project. You should avoid making the concrete too thin, or soupy, as excess water will weaken the finished concrete, and will also allow the aggregates to separate out of the mix.
Continue mixing for a minute or two to completely mix the water into the concrete mixture. Concrete hardens through the process of hydration, so continuing to mix the material will insure the reaction will occur completely.
Place your concrete into your form, smoothing the surface with a shovel or other tool so any additional concrete you need to finish the job can be easily estimated.
Float your concrete after it is placed and rodded off with a straight-edge or screed board. You may want to pat the concrete with your finishing tool to compact the material, removing any voids or air pockets which have formed as you placed it.
Finish the concrete according to your own requirements or the requirements of the project design.
Barricade the area around the concrete to prevent passersby from stepping into it (which could ruin your finished project) and allow it to set and cure. Clean and put away your tools, clean up the area, and remove the empty bags when you are finished.

Tips

Buy premixed concrete in bags you are comfortable handling. 80 pound bags which must be lifted several times, carried great distances, or otherwise handled excessively may be too much for you, so consider purchasing the product in smaller bags.
Have a good water source ready before you begin. This will allow you to mix all your material, clean up tools, and clean up any spills that occur while you work.
Have a plan and a place to rid yourself of any excess concrete.
If you have (physically strong) assistance, bag concrete can also be mixed and poured easily from a strong tarp, pour dry mix onto the tarp, pour water into the depression (as above), then with your helper, pick up the 4 corners and shake and roll the mix together until it blends (90 seconds or so). This methods requires holding a pretty hefty amount of weight up in the air for a while, but many people find it is a very quick and easy method.
Technically speaking, concrete is what cement with aggregate is after adding water. ie; wet.

Warnings

Use a dust mask or respirator, safety glasses, and chemical resistant gloves when using concrete.
Concrete mixtures can set up more rapidly than expected, so be prepared, and get help if needed.

Things You'll Need

Premixed concrete mix
Shovel
Container for mixing
Finishing tools
Clean water
Safety equipment

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Tuesday, October 21, 2008

Use Prepackaged Concrete Mix - wikiHow