Is Rebar needed in a driveway?

The best option for your driveway reinforcement is welded wire mesh/fiber mesh. The mesh consists of galvanized panels of welded wire. Heavy gauge welded wire mesh panels can provide reinforcement for driveways that are not routinely driven on by heavy vehicles such as construction vehicles or industrial trucks. Mesh is typically used by contractors who pour driveway concrete to a thickness of 4 inches because it is a thinner reinforcement and less expensive than rebar.

Concrete Solutions

Is rebar needed in a driveway? There are conditions where it is, and there are places where building codes or engineers require it, but in most cases, there isn’t what I would call a compelling need for it. If the concrete has control joints and expansion joints installed correctly, and if the concrete is placed on stable, well-compacted earth, and if the concrete mix is appropriate for the use, rebar isn’t critical to the driveway’s performance. Often, long driveways are placed by backing a concrete ready mix truck down the center, between the side forms, and then the concrete is poured as the truck pulls forward, towards the road or street the driveway connects to. This makes installing rebar or even wire mesh reinforcing problematic, since backing a loaded concrete truck on top of the mesh is going to result in a mess. Another issue, driveway pouring is usually fast paced, so unless the rebar is thoroughly supported, it will end up on the bottom of the slab.

Rebar is almost never installed correctly in driveways, costs more money, and provides no benefit on account of its inevitable incorrect placement. If the steel is un-coated, it will rust and corrode on account of the wet and alkaline environment. Rusting steel expands, causing the concrete to crack, leading to more water infiltration, leading to faster rusting, leading to more expansion, leading to wider cracks. If the steel is epoxy coated, it never bonds to the concrete and does not do anything. Leave the steel out and make the slabs an inch thicker. Proper control of joint spacing and sealing is important.

Put in order of importance, in my experience, reinforcing is not top priority. Here is the issues that effect the performance of the concrete in a driveway:

Properly prepared base, compacted and graded to a reasonable tolerance.

Handling the concrete properly, that is, not adding excessive water, or allowing it to stay in the truck until it gets hot.

Finishing it correctly, making the surface rough enough for traction, either a sack or rough broom finish, and flat, without bird baths, while allowing drainage, sloping gently so rainwater flows off the slab without creating gullies.

Curing the concrete properly.

Laying out control and expansion joints so the slab cracks where it is supposed to, rather than letting it choose where it wants to crack.

Placing the concrete in moderate weather. Concrete doesn’t perform as well when it is placed in really cold, wet weather, nor does it do its best in very hot, sunny weather. Granted, you might not have a choice here.

Using a good design mix, including air entraining modifiers, water reducers, and using a sufficient strength design mix (usually, 3000 PSI concrete is plenty)

Using Rebar

If you can afford a Rebar driveway, it will need to poured at 6 inches minimum. This is because rebar is comparatively thicker than galvanized mesh reinforcement. The proper way to use rebar reinforcement is to ensure that it is laid in the center or slightly above the center of the slab's thickness(18 inches on Center, crossed). To do this, concrete pros prop up the rebar grids on special metal or plastic supports, called "chairs." It's also possible to use bricks and other scrap material for supports, but this can create weak spots in the slab. Rebar grids are constructed by laying the pieces of bar in a perpendicular pattern, with even spacing. The bars are tied together at each intersection with metal wire. The edges of the grid should be kept at equal distances from all sides of the slab, and the minimum coverage of concrete must be maintained throughout the slab.