Quick Answer: What Type Of Gravel Goes Under Concrete?

Do you need rebar for 4 inch slab?

No, you do not need rebar for a 4-inch slab of concrete on grade.

A 4-inch-thick slab cast on the ground and in permanent contact with it will float and rebar is not required.

Rebar is recommended on concrete measuring 5 – 6 inches thick..

Is sand a good base for concrete?

Pour concrete over a solid, well-drained base of sand or gravel over clay and other poorly draining soils to provide even support.

Should you put plastic under concrete?

Recently, though, research has shown that the old traditional layer of 6-mil Visqueen (polyethylene plastic) under the slab is seldom effective for two main reasons: Although it may seem water-tight, this grade of material allows a lot of water vapor to pass through.

How do you prepare the ground before pouring concrete?

Preparation is the most important aspect of pouring a concrete slab.Dig the ground down to the proper depth. … Smooth out the ground with the flat side of a rake so that you have a level surface. … Tamp the ground with a hand tamper or mechanical tamper. … Pour 2 inches of small, rounded gravel for additional drainage needs.

Should I wet gravel before compacting?

It will vary by situation. Try and wait for the ground to dry if it is a little wet before compacting, but if its unavoidable, add a small amount of large gravel to help bind the wet surface and continue compacting.

What size gravel is best for concrete?

Medium crushed stone (5mm to 2cm) is ideal for use as a layer on top of a larger crushed stone foundation. The medium stones will settle into the gaps between the larger stones and provide a stable and supportive layer for concrete. Medium crushed stone is also used in most general concrete applications for buildings.

What is the best base for a concrete slab?

The base course material, according to ACI 302, “Concrete Floor and Slab Construction,” should be “compactible, easy to trim, granular fill that will remain stable and support construction traffic.” ACI 302 recommends material with 10 to 30% fines (passing the No. 100 sieve) with no clay, silt, or organic materials.

Is gravel needed under concrete?

Whether you pour concrete for a walkway or patio, a strong gravel base is required to prevent the concrete from cracking and shifting. Gravel is especially important in clay soil because it doesn’t drain well, which results in water pooling under the concrete slab and slowly eroding the soil as it finally drains.

How much gravel do you put under concrete?

Excavate the slab area to a depth of about 7 inches, allowing 3 inches for a gravel base and 4 inches for concrete.

What can I use to fill under concrete?

A sand-cement grout can be used to fill voids under concrete slabs. This mix of sand, cement, and water is pumped through holes drilled to fill up the voids. While this method of slab jacking is cost-effective, there are major drawbacks to opting for this type of repair.

Can you pour concrete on gravel?

Cement mix might work in some cases over an existing gravel driveway. Laying a concrete driveway over an existing gravel one is possible, but it is not generally recommended. The kind of gravel that is intended to go under cement is typically a smaller grade than what is used for gravel driveways.

Can you have too much gravel under concrete?

Any more depth of gravel is ok with the proviso that it be well compacted. That means putting it down in thin layers and compacting the *&$%$# out it each time. When you are ready to pour your slab after a couple years check the grade and maybe put in a little more gravel if you need it.