Fox Blocks
Airlite Plastics Co.
6110 Abbott Street
Omaha, NE 68110
877.369.2562
www.FoxBlocks.com
Concrete Placement in Fox Block Corners
Fox Blocks stay-in-place insulating concrete forms (ICFs) are used in all types of residential and commercial
applications. Fox ICF walls provide unparalleled energy efficiency, safety, durability and comfort.
The Fox Blocks ICF features a flat interior configuration. It contains plastic polypropylene ties or studs that hold the
form together during concrete placement and later serve as the furring strips for fastening interior and exterior finishes.
Concrete Mix Design
One of the most important aspects of concrete placement is the proper concrete mix design. Proper concrete mix will
save time on labor, facilitate concrete consolidation and ensure a successful Fox Blocks wall pour. Cutting corners on
the concrete mix can add cost and problems when you place the concrete into the Fox walls.
Concrete mix can vary from region to region throughout the country because the raw materials differ from region to
region. Therefore, you must work closely with your local concrete supplier and explain that you will be placing the
concrete in ICFs. Although Fox Blocks can provide concrete mix guidelines, we cannot provide the specific mix design
for your area.
Concrete Mix Guidelines
The following concrete mix guidelines must be conveyed to the concrete supplier. The concrete supplier has the most
knowledge about the materials in the area and will design the best mix for your Fox Blocks ICF project.
Concrete Compressive Strength
The 28-day compressive strength of the concrete must be specified to meet the strength used in the design of the Fox
walls. The minimum strength that should be specified is 2,500 psi (17 MPa). A slightly higher compressive strength of
3,000 to 4,000 psi (20 to 30 MPa) can help the flowability and pumpability of the concrete and provide additional
strength to the walls with minimal or no additional costs.
Slump
The proper slump allows the concrete to flow and be pumped at an efficient rate. Inadequate slump can create voids
and honeycombs in the walls or put excessive pressure on the forms during concrete placement. Fox Blocks
recommends a concrete slump as shown in the table below. The slump specified must be the slump that arrives in the
cement truck at the job site. Water should not be added to the concrete at the job site. Additional water will reduce the
compressive strength of the concrete and affect the water to cement ratio.
Form Size
Slump
Maximum Aggregate Size
9 1/4" (228 mm)
6.5”-7.0” (165 – 178 mm)
3/8" (9.5 mm)
Fox Blocks
Airlite Plastics Co.
6110 Abbott Street
Omaha, NE 68110
877.369.2562
www.FoxBlocks.com
11 1/4" & 13 1/4" (279 & 330
mm)
5.5”-6.5” (140 to 165 mm)
3/8" to ½" (9.5 to 12.7 mm)
15 1/4" & 17 1/4" (381 & 432
mm)
4.5”-5.5” (114 to 140 mm)
¾" (19 mm)
Aggregate Size
The aggregate size is also important in providing concrete with the proper strength that will flow well through the
forms. A maximum aggregate size as shown in the preceding table is recommended for the best results. If the
aggregate in the forms is too large, it could create damming of the concrete within the forms resulting in a void.
Admixtures
Admixtures are ingredients in the concrete other than Portland cement, water and aggregates. They improve the
pumpability, durability and workability of concrete and prevent weathering. There are many different types of
admixtures available in different parts of the country. Some of types of admixtures include air-entraining, waterreducing, super plasticizers, retarding and accelerating. Fly ash, air, plasticizers and super plasticizers are common
admixtures used in concrete in the insulating concrete form industry. The concrete supplier should address admixtures
at the concrete mix design stage. The goal should be a good flowable concrete mix.
Concrete Placement
The concrete should be placed in four-foot (1.22 m) lifts to ensure proper consolidation. If more than one pour per
project is planned, the walls are typically poured one story at a time. The concrete is placed in the four-foot (1.22 m)
lifts using several passes around the perimeter of the building until either the top of the wall is reached or until the first
pour is complete. Concrete should be placed below every window opening through the opening left in the sill of the
window buck.
Most Fox Blocks builders have found that using an overhead boom pump is the most efficient way to place the
concrete in the ICF walls. When using the overhead boom pump, it is important to slow the velocity of the concrete by
reducing the diameter of the hose near the end of the line. This can be accomplished by using the Ruff-Neck by Con
Forms. Avoid using heavyweight metal devices near the end of the hose.
As the concrete is pumped, it should flow in front of the hose at a 45-degree angle inside the forms. Avoid placing
concrete directly in the corners of the forms. The Fox Block wall should be checked to be sure it is plumb, square and
straight before, during and after the concrete is placed. Always wear protective clothing and eyewear when mixing and
placing concrete. Concrete is a caustic material that can burn exposed skin.
Concrete Consolidation
A good flowable concrete mix is the first step towards ensuring a well consolidated solid concrete wall. Additionally, to
prevent voids and honeycombing and ensure that solid contact is made with the reinforcement bars, it is very important
Fox Blocks
Airlite Plastics Co.
6110 Abbott Street
Omaha, NE 68110
877.369.2562
www.FoxBlocks.com
to consolidate the concrete as it is being placed in every lift. While ICF professionals often employ various methods to
accomplish this, Fox Blocks recommends using the internal vibration method.
Internal vibration can be used with a light-duty pencil vibrator. The wand should not be greater than 1” (25.4 mm) in
diameter. When vibrating the wall internally, always keep the vibrator moving fast in and slow out. Do not leave it in
one spot very long. This is the best method but appropriate caution should be used to avoid deflections or blowouts in
the wall.
Internal vibration has proven to be performed effectively with the Reward product without creating bulging or
blowouts within the wall. The Fox Block has plastic tie inserts spaced 8 inches (152.4 mm) on center that support the
foam panels every 48 square inches (0.031 m2). This provides a strong form for placing concrete and internally
vibrating the wall.
Fox Blocks
Airlite Plastics Co.
6110 Abbott Street
Omaha, NE 68110
877.369.2562
www.FoxBlocks.com
Concrete Placement in Fox Block Corners
In order to achieve successful installation of a Fox Block ICF project, it is important to understand and use proper
techniques when placing concrete in the corners. By following the planning, layout, bracing and securing, concrete
placement and concrete mix procedures in this construction bulletin, you can successfully place concrete in your
Reward walls each and every time.
Layout and Planning
The first step to a successful pour involves studying the building plan to determine where the "outlet" will be for the
concrete to flow. As a rule of thumb, determine which corners have either a door or window or another corner within
12 feet (3.66 m) or less from them. Use outside corner braces on these corners. When doors, windows and corners are
close to each other they create greater concrete pressures on the corner. The closer the doors, windows and corners are
to each other the stronger the outside corner bracing needs to be.
Bracing and Securing the Corner
Secure and level first course of forms to the footing or slab using one of the following methods:
1. Foam glue (EZ FLO Foam)
2. 2 ½" x 2 ½" (63.5 x 63.5 mm) 90-degree bent light-gauge metal tracking
3. 2x wood runners
On each succeeding course, secure each corner to the adjacent straight forms to keep them from separating during
concrete placement using HV Clips. Use corner bracing only in situations as described in the previous section. Bracing
is not required for the corners located more than 12 feet (3.66 m) from doors, windows or other corners, so in those
areas simply use the standard 6-foot (1.83 m) spacing for bracing along the lengths of the walls.
Concrete Placement
For concrete placement, Fox Blocks recommends an overhead concrete boom truck. The end of the concrete hose
should be reduced to 3-inch (76.2 mm) diameter with either a double 90-degree bend or "S" attachment at the end of
the hose or Ruffneck by Conforms.
Place the concrete so that it "pyramids" up in the corners. In other words, the concrete should be at its highest point in
the corner. Never direct the hose or concrete directly into the corner. You can pyramid the concrete by holding the
hose steady at a point on one side of the corner about two to three plastic ties away from the corner for 5 to 15
seconds. Then quickly move the hose to the other side of the corner for 5 to 15 seconds. This will create the pyramid
of concrete and get the concrete flowing away from the corner. It is very important that the concrete slump allows the
Fox Blocks
Airlite Plastics Co.
6110 Abbott Street
Omaha, NE 68110
877.369.2562
www.FoxBlocks.com
concrete to flow down from its pyramid in the corner and flow out at about a 45-degree slope. If the concrete is
bridging up too quickly, the concrete mix is too stiff.
The concrete slump is very important. The concrete should be at a slump that allows the concrete to flow down from
its pyramid in the corner and flow out at about a 45-degree slope. If the concrete is bridging up too quickly, the
concrete mix is too stiff.