Pouring an ICF Project
Welcome to the BuildBlock ICF Installer Training Series: Pouring an ICF Project. This 20 part video series is intended to be an educational walk through of the ICF building process. From the early planning phases to pouring concrete and finishing walls, this series will provide the basic knowledge you need to have a successful BuildBlock ICF build.
In video number 14 we explain the basics of pouring or pumping concrete into an ICF structure. We also discuss proper concrete mix, options for pumping and pouring, how to properly flow concrete, and how to pour corners and openings.
The videos in this series are produced as a companion to the BuildBlock Installation and Technical Manuals available for free download on the Publications Page or for purchase via the BuildBlock Online Store. You can view more videos in this series via the BuildBlock Blog or by subscribing to the BuildBlock YouTube Page. For a more in depth training experience you can take the free Online ICF Installer Training Series.
Pouring an ICF Project
You’ve set the foundation, stacked and braced the ICF walls, placed rebar throughout, and inspected every aspect of the structure… Let’s pour some concrete. This video will help you to understand the basics of pouring or pumping concrete into an ICF structure. We will also cover the proper concrete mix design, options for pumping and pouring, how to properly flow concrete and how to pour corners and openings.
Recommended Concrete Mix Design
The general ICF mix design should be a 3000 psi concrete. Higher strength can be used, but lower is not recommended. In Canada this is a minimum 20 mpa.
The aggregate should be 3/8” (10mm) rock chip or river rock. A 1/2” (12mm) aggregate can be used, but will require more vibration to ensure proper consolidation.
The concrete slump should be between 5”- 6” Be aware as the concrete is being pumped under pressure, it loses approximately 1/2-inch of slump out of the pump hose so you may add ½” slump to the supply concrete going into the pump hopper.
When pumping concrete, do not aim it at an ICF form, the pressure could damage the block. Instead, allow concrete to fall straight down until it begins to build up a mass of concrete. Let the concrete flow naturally. When pumping, push the concrete flow at a 45 degree angle so that it flows smoothly in the direction you are moving. This ensures blocks are not damaged and helps reduce the possibility of trapping air.
Good communication is critical when pouring concrete. Work closely with the pump operator to pour smoothly. Discuss the type of pump and nozzle needed with the pumper before ordering.
BuildBlock recommends a boom pump when pouring a full wall. Utilize a restrictor end, such as a double L nozzle, on your boom hose with a 3 inch end maximum to reduce concrete surge. Work in a decided direction, keeping in mind that a concrete pour should typically end where it began.
Corners and Openings
Take special care when pouring concrete around corners and openings. Flow concrete towards the corners as opposed to pouring directly into the corner. Stay at least 3 feet away from corners until concrete is close to the top and you’re ready to top it off.
When pouring around an opening such as a door or window, anchor each side with a small amount of concrete before pouring the first lift. If necessary, you can fill from the concrete inspection ports below openings before pouring from the top of the wall.
Pouring in Lifts
Pouring concrete walls are typically done in lifts. A lift is a specified height that concrete is poured to at any one time in a continuous pour. Concrete when poured will begin an initial set or slake. The timing on this will vary based on temperature, humidity, and other weather conditions, but is typically 30 to 45 minutes.
This initial slake relieves the amount of pressure on the lower ICF forms and is usually about the amount of time it takes to work around the structure back to the beginning. Concrete should be vibrated at each lift to ensure that it is in its finial consolidated position and free of air voids before the initial set.
Align the wall as each lift is poured as well. This is especially important in tall walls. Take the slack out of the bracing as the wall is poured. You should feel a slight pressure on the brace, but the wall should not actively move.
Working around the structure, ICF lifts are poured to a height of 4 feet. The initial 4 foot lift should reach the bottom sill of windows so that consolidation can be accomplished during the first lift. Once you reach where you first poured, continue pouring, repeating the process 4 feet at a time. This process is repeated until the full height of the ICF wall is reached.
Typically a total wall height of no more than 16 feet is poured at one time. This is the recommendation of most bracing manufactures as well. The time difference between pouring in multiple lifts or all at once is negligible since concrete is pumped at a consistent rate.
When pouring large jobs that have very long running walls it may be advisable to split the pour into two or three sections so that team can properly place, consolidate, level concrete, set anchor bolts, and align walls before the concrete sets up especially at door openings.
In multistory structures, stop pouring concrete 3-4 inches down inside top course forms. This prevents a cold joint seam from being created at the same level as the interlock when the next course of blocks is added. This only applies to the top course between levels.
Protect the top interlock with tape or metal track if continuing up the wall with another story. Place sufficiently high vertical rebar in the top course as specified for lap requirements.
Following these basic steps when pouring ICF walls will ensure a safe and secure project every time. Review the BuildBlock Technical & Installation manual for more detailed information.