Many large slabs are split into several separate pours on different days. Sometimes, if the next section is scheduled in a different construction phase, months can pass before the nextion section is poured. And you can't just pour two slabs next to each other and have them meet the structural requirements of your project; you must join the two concrete slabs in the proper way. Joining slabs involves creating a joint that both structurally connects the slabs and provides a flexural point to accomodate how the different ages of the slab will respond to climate and stress. While it sounds complicated, the proces to join two concrete slabs is easy but might take a few attempts to get it right.
Things You'll Need
- Project plan
- Tape measure
- Lumber crayon
- Hammer drill
- Compressed air
- Concrete epoxy adhesive
- Epoxy gun
- Rebar dowels
- Expansion joint material
- Box cutter
Consult your project plans to determine the spacing of the rebar that was placed in the first slab and the spacing of the rebar that is to be placed in the second slab. Measure and mark the side of the concrete where the two slabs will be joined with points where you will need to drill and epoxy splice dowels. You want to offset the dowels, at the dowel's width, to the rebar spacing. For example, if both slabs have rebar mats that are spaced at 18 inches and use No. 5 rebar, then measure and mark for your dowels at a 18.5 inches of spacing (18" + 1/2" diameter of the rebar). If your two slabs have different spacing for their rebar mats, measure and mark so your dowels fall in the middle of the spacing of the second slab. For example, if the first slab is at 12 inches and the second is spaced at 18 inches then measure and place your first mark at 9 inches and then continue spacing the marks at 18 inches. This will place the dowel in the center of the second slab's rebar spacing.
Drill out the holes for your dowels using a hammerdrill. Drill the exact depth specified in the General Instructions section at the front of your project plans. Make sure you use a drill bit that is equal to or slightly larger than the rebar dowel you will be using.
Clean out the holes by blowing them with compressed air.
Load your concrete epoxy adhesive into the epoxy gun according to the instructions included with the gun. Insert the tip of the epoxy gun into the hole as far as you can. Fill the hole with epoxy slowly. Pull the tip of the gun out of the hole as it fills.
Insert your rebar dowel into the hole. Push the dowel in and out several times to get rid of any air pockets in the hole before pushing it in as far as you can. The rebar dowel size will also be specified in the General Instructions section of your project plans. Let the epoxy set for the length of time specified on the package.
Run a bead of concrete epoxy on the face of the edge of the first concrete slab, above and below the dowels. Cut your expansion joint material with a box cutter so you can press two strips onto the concrete (above and below the dowels) the entire length of the edge. You are now ready to pour your slab.
- Photo Credit Jupiterimages/Creatas/Getty Images
How to Tie Driveway Slabs to Garage Concrete
Tying a driveway slab to a concrete garage floor stabilizes the driveway and prevents it from separating from the garage. The process...
The Best Way to Lay Rebar in Slab
A concrete slab has to support the weight of the structure above it plus anything that may be placed on top of...
How to Connect a Concrete Slab to a Concrete Footer
In many instances a concrete slab may be connected to a concrete footer rather than the slab "floating" on top of the...
How to Set Anchor Bolts Into Concrete With Epoxy
Chemical set, or epoxy anchors, use a two-part epoxy adhesive to hold the anchor bolt in the concrete. To ensure that an...
How to Attach New Concrete to Old Concrete With Pins
When joining new concrete work to old concrete work, the joint will always develop a crack and will be a point of...
How to Pour a New Concrete Slab Over an Old Concrete Slab
Concrete is a durable construction material and has many uses around a house. Masons pour concrete for driveways, sidewalks, foundations, patios and...
How to Join Two Pieces of Melamine
You’ve finished cutting the melamine boards for a bookshelf, and you would like to join the boards together without revealing unsightly screws...
How to Glue Marble Slabs Together
Marble is a strong material, but it can break. Too much pressure can break a piece of marble, and a heavy object...
Types of Joints in Concrete
Most drivers are familiar with the inevitable "thump, thump" noise while driving on roadways. During the construction process, a number of concrete...
DIY Concrete Expansion Joints
Concrete expansion joints are absolutely essential for large concrete slabs in order to prevent the expansion and contraction of the concrete from...