How to Mix Concrete
Concrete is a valuable building material around the home. Strong, adaptable, and durable, concrete can be used for patios, fence posts, flooring, footers, and slabs. You can even make kitchen countertops, bathroom vanity tops, and sinks out of concrete.
While concrete mixing is commonly associated with mixing trucks and commercial-grade mixers, home do-it-yourselfers can reliably mix up small quantities of concrete with simple tools.
It is possible to mix smaller quantities of concrete by hand, without using an electric mixer. You will use just a garden hoe and shovel, a mixing basin such as a wheelbarrow, and a clean water source such as that from a garden hose.
How Much Concrete to Mix at a Time
Batch quantities with this method are limited to one or two 50-pound bags of concrete. Mixing more than 100 pounds of concrete with a hoe is physically difficult, plus the concrete may begin to harden before you can get the entire batch mixed.
Most do-it-yourselfers will find that mixing one bag of 50-pound concrete at a time is the most comfortable batch quantity.
How Much Water to Add to the Concrete Mix
Measuring out the exact amount of water is crucial to successful concrete mixing. Using not enough results in a dry, powdery mix that doesn’t stick together or set properly. A more common error is to add too much water. While the pour may be successful, concrete mixed with too much water is weak and will soon crumble.
While you should aim for the exact amount of water specified by the manufacturer, most manufacturers build in tolerances for extra water, if needed. In many cases, you can add up to 2 extra cups of water.
Tips For Increasing Concrete Working Time
Quick-mix concrete begins to set in around 20 to 40 minutes. This means that you have less than 20 minutes to fully mix the concrete and pour it.
To maintain these tight parameters, you’ll need to have all of your materials and tools ready and nearby. Every extraneous action only cuts into the concrete’s working time.
With the garden hose, pour out 8 cups (or 1/2-gallon) of water in the measuring cup and then into the bucket. Mark the waterline with the indelible marker.
Place the hoe, shovel, bucket of water, measuring cup, and garden hose (faucet on, hose controlled with a sprayer) within reaching distance of the wheelbarrow.
Mix the concrete as close to the pour site as possible.
Work with an assistant. One person devotes their attention to mixing, while the other person adds water and steadies the wheelbarrow.
If working alone, brace the wheelbarrow while mixing the concrete by stepping on one of the wheelbarrow’s stands with your foot or by supporting the side of the basin with your knee.
Concrete achieves 400 psi of compressive strength within about two hours and 1,000 psi within 24 hours. Concrete is considered fully cured in 28 days, but it is usually useable in about a day or two, depending on the application.
Pour Out the Bag of Concrete
For a clean pour that minimizes dust, set the bag of concrete on-end in the wheelbarrow. Hold the top of the bag with one hand and use the other hand to slice off the top of the bag with the utility knife. Gently push the bag on its side and slowly pour out the concrete mix. Keep the mix sequestered on one side of the wheelbarrow or mixing basin for now.
Pour the Water
Pour the prepared bucket of water into the open side of the wheelbarrow or basin.
Slowly Fold Concrete In With Water
With the hoe, gradually pull material from the concrete side of the basin into the water. Make sure that the product is mixed into the water before pulling in more of the product.
Mix the Concrete Together
When all of the concrete and water are mixed, continue to mix until you remove all air pockets or dry sections.
Assess and Amend the Concrete If Needed
The concrete should have a peanut butter-like consistency. It should not be soupy. If so, add a small amount of dry concrete to stiffen the mix. Nor should the mix be powdery. If so, add up to 2 cups of water, one cup at a time.
Drag the hoe once through the mix, with the hoe touching the bottom of the basin. The concrete groove’s sides should stand firm. When you pat the concrete with the hoe or a shovel, it should remain flat.
Clean the Tools
Immediately after pouring the concrete, clean the tools (unless you will be mixing up more concrete). Put the tools in the wheelbarrow, spray them clean, then stand them up to the side to dry. Spray the inside of the wheelbarrow clean of all concrete residue.