DIY Concrete Slab in Sections

DIY Concrete Slab in Sections

Laying larger concrete slabs sometimes requires that you pour the slabs in sections. Each section becomes an individual slab, separated by a small wall of material known as an expansion joint. The expansion joint helps prevent cracks that can form in a slab from the slight expansion and contraction of the concrete due to temperature changes. They act as a wall between each section, forming points in the slab for tension release. The addition of expansion joints allows even the DIY builder to create large level expanses of concrete suitable for any use.

Instructions

Things You'll Need

Concrete pumper truck

Rebar

Blocks of concrete

Expansion joint strip

Utility knife

Long-handled hook

Concrete come-along

Screed

Shovel

Bull float

Metal float

Trowel

Joint sealing compound

Plastic sheeting

Bricks

1

Use a concrete pumper truck to haul in concrete for larger slab creation. Schedule the truck's arrival at the slab site one hour before you plan to pour to set up the truck location and determine the best methods of coverage with the operator.

2

Prepare the foundation hole for the concrete by placing the reinforcing bar onto blocks of concrete half the height of the proposed slab.

3

Place the concrete pumper truck so it sits on level ground away from any holes or back-filled areas for stability.

4

Determine the locations of the expansion joints. Place the joints so they section the slab into areas no more than two to three times the thickness of the slab. For example, a 4-inch thick slab should have a joint every 8 to 12 feet.

5

Cut the joint material, usually cork, rubber, foam or wood, with a utility knife into strips long enough to span the width of the poured slab. Make sure the strips are the same height as the slab and no less than 1/4-inch thick. Place joints in the pre-determined locations.

6

Pump the concrete into the first slab section, starting at a corner of the section and pumping in along the edge. Place the concrete in parallel strips, working from the top of the section where you began to the bottom until you finish filling a section of the slab in the opposing corner from which you began. Turn off the pump when a section is completed.

7

Use a long-handled hook to keep the rebar from falling off the support stones in the slab from the weight of the concrete. Pull slipping rebar back into place with the hook, maintaining its position in the center of the slab.

8

Use a come-along to pull the concrete level, then screed the surface of the section while it's being poured to smooth the surface. Fill any low spots after screeding with shoveled concrete.

9

Stand up the joint strip vertically at the edge of the poured concrete section pressing it firmly against the concrete.

10

Pour the adjoining section starting at the joint strip, following the same pouring method as the first section. Make sure to pour the new section before the previous section sets. The weight of the concrete on both sides will hold the strip firmly in place, incorporating the strip into the slab as the concrete cures.

11

Use a bull float on the surface of the concrete to level any voids and to push the concrete aggregate throughout the slab.

12

Smooth the edges of the slab with hand-held metal floats.

13

Wait for the concrete to set to the point where it can support your weight. Setting times vary according to weather conditions and the strength of the concrete used. Trowel the set concrete to smooth the surface. Make certain the expansion joint strips aren't covered, scraping away concrete over the joints.

14

Place a strip of joint sealing compound formulated for the joint type along the top of the expansion joint to prevent water from working its way to the bottom of the slab along the side of the joint strip.

15

Cover the concrete with plastic to prevent it from drying out too quickly and allow it to cure for the length of time suggested by the concrete manufacturer. Weight down the edges of the sheeting with bricks to prevent its blowing away.

Posted in: Concrete,slabs