3.28 CONCRETE PLACEMENT

Concrete can be placed using a bucket, chute, conveyer, grout pump or “boom” pump truck. When utilizing a “boom” pump truck, specify a double 90° (S) toward the end of the hose to break the concrete’s fall, ending with a 3” or 4” nozzle. (Some states/regions will not allow double S hose.)

Recommended:

• minimum 2500 PSI
• up to ¾” for 8” 10” & 12” forms. ⅜” for 4” & 6”
• 5½” to 6½” Slump
• Pour 10° to 100°+ F

Start concrete placement in a wall with few or no openings. This allows you an area to be sure everything is correct – slumps good, pumps working, ect. Move around structure. When you come to a corner – do not pump directly into the corner – let it flow in from the side. Do not pour into the top of a T. When pumping at windows it is easiest to pump from both sides creating a ‘V’ under the sill. Fill in the ‘V’ from the window and move down the wall. Other crew members can screed that sill, place the 2x sill plate on and cross brace it or, place concrete under windows first, proceeding to walls.

Pour lift heights are based on many factors. A very safe pour height is 4 feet. However most installers place in 8” - 10” lifts. Use discretion and place what you are comfortable with.

Concrete consolidation is important for obtaining a structurally sound wall. You can use a pencil vibrator (1 inch head or less) to consolidate. Be sure you have someone with experience run the vibrator. They should know “fast in, slow out – and always moving” (slow out is approximately 3 inches per second). There are times you can move concrete within a wall by “rodding” or “thumping”.

After concrete has been placed in a wall, you have approximately 60 to 90 minutes to align and plumb the wall. Any time period over that and you may not be able to move it. The 60 to 90 minutes varies depending on concrete mix, air temperature, air humidity, and other factors. Greenblock recommends that a wall be checked and aligned/plumbed as soon as possible after being poured. (15 to 20 minutes). In extremely hot or cold weather cover the walls after pouring. If it looks like it might rain or snow – cover the walls after pouring. A top plate can be a fast and effective cover depending on how it is installed.

Calculate amount of concrete needed by using the Net Wall Square Footage:

4” core*
• Approximately one yard of concrete for every 81 square feet of wall

6” core*
• Approximately one yard of concrete for every 54 square feet of wall

8” core*
• Approximately one yard of concrete for every 40 square feet of wall

10” core*
• Approximately one yard of concrete for every 32.4 square feet of wall

12” core*
• Approximately one yard of concrete for every 27 square feet of wall

* Subtract 1 sq ft of concrete per 90° and 45° corner block used when using the 6” and 8” systems.

TIP: If you encounter a problem during the pour - !STOP! - Especially if you are pouring with a minimal crew. Solve or resolve the problem – then move on.

If a problem develops, stop the pour, resolve the problem – otherwise you may end up with multiple problems.

Stay in control of the pour – be mindful of:

• Pouring conditions
• Slump
• Wall thumping for voids
• Bolts pushed in
• Window bucks installed and braced
• Door bucks braced across bottom
• Concrete truck turn around times
• Door cross bracing installed
• Concrete consolidation
• Wall alignment
• Wall bowing or bulging
• Form lifting
• Time of day