How to Pour Concrete

Building your own walkway, driveway or other concrete project is easier than you think.

With a bit of planning, concrete knowledge and a lot of honest work, you can pour your own concrete patio, sidewalk, retaining wall or slab foundation.

The basics of concrete include deciding on the right type of concrete, estimating how much concrete is needed to complete the project, building the forms, mixing and pouring, reinforcement, finishing and letting it cure properly.

Read on to learn the fundamentals of concrete form building, mixing and pouring.

What Type of Concrete Should You Use?

For small jobs like reinforcing fence posts or smaller projects like concrete walkways, you can use Ready-mix concrete, which comes in 25 pound bags.

For larger projects you’ll want to order Transit-mix concrete to be delivered by a truck with a revolving barrel, which is more costly but saves a huge amount of time, or else rent a trailer and transport it to your jobsite, which can save you money.

If you have the time, you can rent a mixer and prepare the concrete yourself onsite, but check around for pricing on all three of these options to determine whether the savings justify the additional work of mixing your own concrete for a large project!

Concrete Materials Estimation

To estimate the amount of concrete you need, you must first know the area and depth of your pour. Multiply the length and width of the area you are covering with concrete to calculate the square footage. Then multiply this number by the thickness your concrete will be.

Refer to the following table to determine how many cubic yards will be needed to complete your project:

Area in square feet
(length x width)

Thickness in inches

 

4

5

6

8

12

50

0.62

0.77

0.93

1.2

1.9

100

1.2

1.5

1.9

2.5

3.7

200

2.5

3.1

3.7

4.9

7.4

300

3.7

4.7

5.6

7.4

11.1

400

4.9

6.2

7.4

9.8

14.8

500

6.2

7.2

9.3

12.4

18.6

Building Concrete Forms

Most concrete projects require forms, either above or dug into the ground. The forms provide a mold to retain the concrete during finishing and curing.

Start by setting up temporary posts to establish the slope or grade, and then lightly nail or clamp the forms to the posts with C clamps. Be sure to use a level in order to be sure the slope or grade is correct.

Once you have set the grade, drive stakes in place along the edges of the shape and size of the area to be covered with concrete and nail the forms to the stakes.

Concrete Mixing

There are four primary ingredients used in concrete; Portland cement, fine aggregate like sand, coarse aggregate like crushed rock or gravel and water.

Between two thirds and three fourths of mixed concrete are comprised of the sand and rock or gravel aggregates, which need to be clean and without organic material. Clean water must be used to mix concrete and should not contain acid, alkali, oil or sulfate.

Even though these basic ingredients are the same for any concrete pour, the mixture varies, depending on the job.

For foundations and retaining walls, use about 6-1/4 gallons of water for each sack of cement if the sand is damp. However, if the sand is wet, 5-1/2 gallons of water will easily do the job.

For a sidewalks, slab or similar job use approximately 5 and three quarters gallons of water for each sack of cement if the sand is damp or approximately 5 gallons if the sand is wet.

To build heavy footings for a wall, where waterproofing is not critical, mix concrete using one part cement, three parts sand and four parts gravel.

To build a sidewalk, driveway or steps, mix one part cement, two parts sand and three parts gravel.

When mixing cement for a small job, you can mix in a large bucket or wheelbarrow. For larger jobs, use a wooden box that is twelve inches in width, length and depth to mix concrete one yard at a time.

Be sure to read the directions on your concrete bags since the exact ratios can vary.

Concrete Pouring

With your forms in place, wet the area lightly using a garden hose, fill the forms with concrete and then compact it by either tamping the concrete, using a piece of 2×4 or, for a large pour, rent a roller tamper.

Once the concrete is tamped, use a 2×4 board with a straight edge as a screed to level the surface, working it back and forth with a sawing motion until the concrete is completely level across the entire formed area.

After the concrete sets enough to support a 2×8 plank, use it as a straight edge, guiding a concrete grooving tool to cut contraction joints spaced every four to six feet, which will allow the concrete to contract and expand with temperature changes.

For narrow areas like sidewalks and walkways, you only need to cut the joints across the concrete, but for large areas like a patio or driveway, joints should be cut both directions at 90 degree angles to each other, spaced every four to six feet, embedding two beveled clapboards of the right length to span the concrete.

One board should be nailed on top and removed once the concrete has set, leaving the second hidden in place to provide adequate contraction, which is more critical the larger the area of concrete you pour.

Concrete Reinforcement

For projects like driveways and slab foundations, steel mesh reinforcement is needed. In cases where the majority of pressure will be from the top of a slab, place reinforcement close to the bottom.

In cases where the slab’s strong point is in the center, with pressure exerted from either end, place reinforcement as close to the top as possible.

Concrete Finishing

Use a trowel and float to create a smooth finish, using the float to smooth the surface overall and then using the trowel to finish.

If you want a lightly swirled pattern in the finish, move a steel trowel across the surface of the concrete with a swirling motion on your final pass. If you want a heavier swirl, use a wood float instead of the trowel and finish the surface sooner, when the concrete is relatively wet.

Drag a soft brush across the surface of moderately wet concrete if you want to create a light pattern of parallel lines; for heavier parallel lines, try doing this while the concrete is relatively wet.

You can use a broom to create a slightly wavy, rough finish that is not slick when wet, making the brush strokes all in the same direction between contraction joints, or alternating the direction for a different look.

If you want your concrete to look like flagstone, after leveling the surface with a float, use a half or three-quarter inch piece of copper, about 18 inches in length and slightly, bent to tool the surface. Then trowel and brush the surface lightly.

Regardless what pattern you use, be sure it will not cause standing water, which is one of the major causes of failure with concrete.
If desired, you can also add a colorant when mixing your concrete to make it look like natural stone, brick, etc.

Let the Concrete Cure

Concrete takes time to cure, during which time you should use a garden hose with a fine mist spray attachment to wet it at least twice per day for the first three days or so after pouring.

While concrete poured indoors can be left uncovered, you should cover exposed concrete with burlap or building paper during the curing period, removing it each time you spray it and then recovering it again.

All concrete must be given time to cure. During this period, the concrete surface should be kept wet by repeated hosing with a fine mist.

Do not pour concrete during the middle of the day if the weather is super hot, since it will dry too quickly. It’s much better to pour toward the end of the day when things are a bit cooler and the concrete can set more slowly overnight without direct sunshine.

Apply a clear or colored sealer to your concrete it is completely cured to improve traction, enhance the appearance and extend useful life.

Concrete Tools and Material Checklist

  • Concrete Mix
  • Level
  • Hatchet
  • Grover
  • Line
  • Concrete Hoe
  • 2x4s and Other Material for Forms
  • Rubber Boots
  • Reinforcing Mesh
  • Garden Hose
  • Darby or Float
  • Tiling Spade
  • Long 2x4s for Screed
  • Brush or Broom
  • Plastic or Galvanized Pail
  • Edger
  • Line Level
  • Trowel
     

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