FAQ

Cellular Concrete is generally defined as a lightweight cementitious material that contains stable air or gas cells uniformly distributed throughout the mixture at a volume greater than 20%. The cementitious materials encapsulate the air bubbles, then dissipate leaving a void structure as a replacement to traditional aggregate.

The pre-formed foam process offers excellent quality control and assurance of specified density. Preformed foam, unlike gas-forming chemicals, assures a consistent three-dimensional distribution of the engineered air cell system. Pre-formed foam produces a consistent matrix of relatively small air cells which are more desirable than a disorganized matrix of different size bubbles often created with the gas off method of reactive admixtures

In the lower density ranges cellular concrete does not develop the compressive strength of traditional concrete. While this may be a disadvantage in traditional concrete applications, it is an advantage in a cellular concrete application. It should be considered that cellular concrete and traditional concrete are typically used for different types of applications. Each form of concrete exhibits a unique family of performance characteristics. Each should be utilized in the appropriate type of project.

No! “Flowable” fill is typically a very wet cement and fly ash slurry mix. Although cellular concrete and CLSM flowable fill are fluid products, and are often both acceptable for the same application or project, cellular concrete exhibits less unit weight as well as enhanced sound and heat insulating properties. Often flowable fill reaches compressive strengths that make removal of the material problematic. Low density cellular concrete is very easy to remove with hand tools only. Technically, cellular concrete is a controlled low strength material, but “CLSM” by definition, commonly refers to cement- fly ash slurries, while “cellular concrete” refers to the addition of an engineered air cell system to cement or cement/fly ash slurry. AERFLOW™ from Aerix Industries is the answer to the demand for an air enhanced CLSM flowable fill product that can be produced at the Ready-Mix concrete plant. AERFLOW™ is an additive that may be added directly to the 1.5 – 2.0 inch slump flowable fill mix without the use of a foam generator. AERFLOW™ CLSM exhibits a high flowablity characteristics and 20-25% air content. CLSM flowable fill no longer needs high water contents and high ultimate compressive strengths. See the product section on AERFLOW™ for further details

Cellular concrete weighs considerably less than typical “lightweight” concrete. By definition “lightweight” concrete is a concrete made with aggregates that are substantially lighter than typical stone aggregates. Typically, lightweight concrete has a density + 120 lb. / cu.ft. Typical cellular concrete, utilizing the internal air cell structure instead of an aggregate, exhibits <20 - >60 lb. / cu. ft.

Unlike traditional concrete there is little to segregate in cellular concrete rendering segregation a moot point. The cellular concrete equivalent to segregation would be a collapse of the air cell system and a volume reduction in material. To prevent this one should use the most stable liquid foam concentrates and treat the mixed cellular concrete with some care in placing. Fresh cellular concrete is not fragile and can be pumped for long distances but conversely neither is it indestructible.

Cellular concrete exhibits a much lighter density than typical aggregate concrete. Typical traditional concrete has a density of >140 lb/cu. ft. Cellular concrete densities range from <20 lbs. / cu. ft. to >120 lb. / cu. ft. Cellular concrete is an insulator and can be used in a variety of applications which require an insulating material that can also exhibit some integrity and strength. Cellular concrete at its lightest density is still more stable and stronger than well compacted soil. When replacing soils, cellular concrete can be designed to provide whatever strengths and characteristics needed for the soil stabilization project. Some soils engineers lightheartedly refer to cellular concrete used in Geotechnical stabilization projects as “designer dirt.” They know that cellular concrete can be specified to easily exceed whatever compacted soil requirements are needed.

Cellular concrete is compatible with common concrete construction admixtures; however, most common admixtures are added to traditional concrete to effect a change in the characteristics of the concrete that are not applicable to cellular concrete application performance. As an example, cellular concrete needs no air entrainment or finishing aids; however, color admixtures and strength enhancing admixtures work well if they are applicable to the project.

Fiber reinforcement Heat-of-hydration reducers (iced water or chemicals) Compressive strength enhancers Coloring pigments or color enhancing admixtures

Typically, a .5 water to cement ratio slurry consisting of two parts cement to one part water is typically used as a base mixture for cellular concrete. The water cement ratio is varied according to specific project requirements. We should note that cellular concrete obtains it’s natural fluidity from the air bubble structure, not from excess water content.

Cellular concrete may also contain normal or lightweight, fine and/or coarse aggregates. The rigid foam air cell system differs from conventional aggregate concrete in the methods of production and in the more extensive range of end uses. Cellular concrete may be either cast-in-place or pre-cast. Cellular concrete mix designs in general are designed to create a product with a low density and resultant relatively lower compressive strength (when compared to traditional concrete). The typical density range of neat cement cellular concrete mixes is 20 – 60 lbs/cu. ft. which develops a corresponding compressive strength range of 50 psi – 930 psi. When higher compressive strengths are required, the addition of fine and/or course aggregate will result in a stronger cellular concrete with resultant higher densities. We should note that most cellular concrete applications call for a lightweight material. When considering the addition of course aggregate, one must consider how appropriate this heavy aggregate will be to a project, which typically calls for lightweight material. The inclusion of aggregate, particularly course aggregate, may be counterproductive to the materials intended performance.

Cellular concrete may be produced with any type of portland cement or portland cement & fly ash mixture. The performance characteristics of type II, type III and specialty cements carry forward into the performance of the cellular concrete.

Fly ash added to the cement does not adversely affect the basic hardened state of cellular concrete. Infusing and supporting the cellular concrete with the air cell system is a mechanical action and is not problematic with fly ash or admixture concrete chemistry. Note that some fly ash mixes may take longer to set than pure portland cement applications. Mixes with large percentages of fly ash may take an very extended time to set up. High carbon content fly ash such as typical “bottom ash” should be generally avoided in most cellular or plain concrete mixes.

In a continuous generation system. the foam liquid concentrate is run through the autofoam generator, which adds air and water to the concentrate to create the pre-formed foam. That foam is then mixed with the cement slurry through an inline injector and then pumped through a hose to the placement location. MEARLCRETE, AERLITE, and AERLITE -iX mixes have been successfully pumped up to 700 ft vertically and 15,000 ft horizontally without any issues.

No, Aerix supplies the advanced engineered liquid foam concentrate to specialty contractors. These contractors with cellular concrete specific training and experience will produce and place the cellular concrete. Aerix has a great working relationship with these specialty contractors and is committed to providing them mix design and technical support throughout the production and placement process.

The cement and water slurry should be mixed until there are no dry clumps or balls of cement. The pre-formed foam mixture is then added into the mixture. The foam mixes quite rapidly into the slurry and only requires modest mixing times depending upon the mixing equipment.

Mixing until there is a reduction of volume of product is not recommended. Air cell stability is the mark of Aerix engineered liquid foam concentrates and our foam generators. With typical mixing procedures, cellular concrete formulated with Aerix pre-formed foam is very stable even with modestly extended mixing times.

Cellular concrete is a very easily pumped, highly fluid mixture. The bulk of cellular concrete is placed by pumping. Cellular concrete typically will move through the pump lines using less pressure than typical heavier grout mixes. Documentation of cellular concrete being pumped up to and exceeding 500 ft. vertically and 10,000 feet horizontally is commonly available.

Most cellular concrete is left to self-seek a level and not surface “finished” in the traditional sense. Much cellular concrete is covered by another material. A floor overlayment type smoother tool can be used simply to break the surface air cells and create a more uniform and polished look to the surface in the rare case when a more uniform surface appearance is desired.

Synthetic fiber reinforcement is a mechanical process and does not have any effect on the chemistry of concrete. It is therefore perfectly acceptable to design fiber reinforced cellular concrete. Fiber reinforced cellular concrete is becoming a standard material for roof decks and Insulated Concrete Form (ICF) construction.

There is no chemical or mechanical reason not to reinforce cellular concrete with steel fibers. However, most cellular concrete applications require a lightweight material. Most steel fiber concrete applications require heavy, high compressive strength steel fiber reinforced concrete. It would seem somewhat unlikely that an application would require steel fiber reinforced cellular concrete, but there is no technical reason not to design a steel fiber reinforced cellular concrete

Not with well engineered liquid foam concentrates. The pre-formed foam cellular concrete products made from top quality Aerix liquid foam concentrates do not collapse. Air cell stability is the mark of a superior foam concentrate and foam generator combination. Which is not to say that all cellular concrete products are stable. Particular care should be taken to test foams from water pressure type foam generators, and gas-off chemical products. The proposed pre-formed foam for an application should be tested for stability or certified for stability before actual project placement.

Cellular concrete follows ASTM test methods that apply to lightweight insulating concrete. ASTM C 495 is the standard method for testing compressive strength, and ASTM C 796 is the standard testing method for foaming agents used in the production of cellular concrete using pre-formed foam.

Yes, handling and storage of cellular concrete samples is very important. Cylinder specimens are 3″ x 6″ and should be stored in 50% relative humidity for curing. Samples should be removed from cylinders and air dried for 3 days before compressive strength testing at 28 days.

Cost effective cellular concrete varies in price by geographical area and by application requirements. YourAerix Industries representative will be glad to assist you with budget numbers and binding quotations for our products. If you wish, your Aerix representative can also coordinate in place pricing through one of many factory trained specialty contractors.

A typical cellular concrete project will be much less expensive cubic yard to cubic yard when compared to traditional concrete due to labor savings, less cost of forming and the price savings when comparing pre-formed foam to aggregate pricing. We should note that cellular concrete is seldom ever used in an application where traditional concrete would be applicable. Comparing prices of cellular concrete and traditional concrete is not a meaningful comparison. Cellular concrete does compare favorably with prices for grout, mortar, and flowable fill.

An Aerix team member can furnish you with written or electronic specifications that are appropriate to your application. Basic specifications can also be obtained via e-mail.