“How thick can you pour cellular concrete?” is one of the most common questions we’re asked about CJFill-UL Ultra Lightweight cellular concrete at CJGeo. Qualitatively, the answer is a solid “pretty deep!”. Quantitatively, the answer depends on a lot of factors. Historically, most specifications gave a limit of 2′ deep. Newer foam technology & high quality generation methods can facilitate pours as deep as 20 feet at once.
Traditional Methods for Determining Pour Thickness
Traditionally, foam chemical manufacturers, such as Aerix Industries, have specified maximum recommended pour thicknesses. For example, Aerix historically recommended a maximum 2′ thickness.
Limitations of Traditional Methods
The ability to pour really deep lifts of cellular concrete is driven by many more properties than the preformed foam. The generation method, and quality, of the paste is actually the biggest driver of possible lift heights. Historic limits of 2′ were based on keeping heat of hydration as low as possible, because organic protein based preformed foams, such as Mearlcrete, would denature at relatively moderate cure temperatures. The thought was to limit heat by limiting mass & thickness. If the foaming agent denatures and the bubbles pop before the paste matrix sets, the material will consolidate, sometimes significantly.
Because synthetic foaming agents, such as Aerlite-ix, do not denature, 2′ limits based on keeping internal heat down are irrelevant.
Factors That Drive Lift Thickness Limits
The appropriate maximum lift thickness is based on a few different factors:
- the area of the pour
- how long the pour will take
- the thermal properties of adjacent materials
- temperature of the adjacent materials
- density of the cellular concrete
- generation method of the cellular concrete
- type of preformed foam being used
- forming
Determining The Maximum Lift Thickness
The best people to determine maximum lift thickness are people who pour thousands of cubic yards of cellular concrete a week. Our contact info is below. But, in general, this is how the various factors drive the answer to “How thick can you pour cellular concrete?”:
Area
Area is important because the biggest driver of how deep a single lift can be is how long it will take. You definitely don’t want to continue pouring into an area after the first material placed has started to set. Moving material after it’s set is a recipe for consolidation. So, if it takes about two hours for material to start to set, you shouldn’t pour in a bigger area than you can place into for about two hours. In mass fill applications, consolidation can cause issues if the in-place density is higher than the designed maximum allowable density.
Time
As discussed above, it’s generally not advisable to place a segment of mass pour for longer than two hours, because material may start to consolidate after that. For utility grouting applications where in-place density is less significant and longer placements are needed, consolidation can be accounted for in planning.
Thermal Properties of Adjacent Materials
Deep pours depend on fast set times. If the adjacent materials have high thermal conductivity (like concrete), the adjacent concrete can absorb a lot of heat and retard set times. Retarding set times can make the material more susceptible to consolidation from environmental vibrations. At low water : cement ratios, the preformed foam bubbles can dry out before the cement paste sets to the point of supporting itself, resulting in consolidation.
Temperate of Adjacent Materials
If the adjacent materials are highly thermally conductive and also very cold, it accentuates the issues discussed above. If the adjacent materials are very warm (such as a south-facing mass concrete wall in the summer), then consolidation is less likely.
Density of the Cellular Concrete
Lower density mixes, such as 25lb/cuft and lower, have the lowest cement content, and take the longest to set, so they are more susceptible to consolidation. As a rule of thumb, the lower the density of the cellular concrete, the shorter timeframe it should be poured at great depths.
Generation Method of the Cellular Concrete
How thick can you pour cellular concrete depends a lot on mixing type. High energy mixing, such as CJGeo uses with our dry batch plants, facilitates deeper lifts. Ready mix supplied slurry, volumetric batching, or paddle mixing, are all low energy, and don’t ensure that the cement particles wet out uniformly. Cement that’s not wet out properly can rob water from the preformed foam, causing consolidation, which is accentuated by pour depth. Low energy mixing methods make material that takes longer to set, and long set times are the enemy of deep ours of cellular concrete.
Type of Preformed Foam
Cellular concrete made with organic preformed foams, such as Mearlcrete, should not be used for deep pours. The best preformed foams for deep pours are synthetic foams, such as Aerlite-iX, and Aquaer-iX. CJGeo exclusively uses these synthetic foaming agents.
Forming
If you’re having to form a pour, particularly if the area is large, shorter forms are easier to manage.
Speak With An Expert
Facing a challenge? Give us a shout or shoot us a text. Click the state marker for the location of the project for contact info for the appropriate rep.
