What is cellular / foam concrete? 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 twenty percent. In lay terms, it can be thought of as a concrete, which utilizes a stable air cell structure rather than traditional aggregate.
What is the correct water to cement ratio for the cement water slurry? Typically, a .5 water to cement ratio slurry consisting of two parts cement to one part of water is typically used as a base mixture for cellular concrete. The water cement ratio is varied according to specific project requirements.
Do cellular concrete mix designs contain either fine or course aggregate? Cellular concrete may contain both 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 precast. Cellular concrete mix designs in general are designed to create a product with a low density and the resultant relatively lower compressive strength (when compared to plain 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.
What type of cement is appropriate for cellular concrete? Cellular concrete may be produce 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. Is it appropriate to add fly ash to the cement and water slurry for 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 concrete Foaming Agent chemistry.
What are the advantages of cellular concrete? Cellular concrete exhibits a much lighter density than typical aggregate concrete. Typical plain concrete has a density of 140 lb/cu.ft. Cellular concrete densities range down to 20 lb./cu. ft.
Are there different methods for manufacturing cellular concrete? Cellular concrete is commonly manufactured by two different methods. Method 1 consists of mixing a pre-formed foam mixture into the cement and water slurry. Method 2 consists of the addition of reactive substances, which produce gas bubbles when in contact with the cement and water slurry.
What are the advantages of pre-formed foam? The pre-formed foam process 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 Foaming Agents
Are there different manufacturers of cellular concrete? Yes! Midwest Cellular Concrete Inc. has experience with all of the highest quality suppliers. ACI Committee 523 is supported by a group of dedicated individuals from several vending companies who represent the cellular concrete industry and work diligently toward the advancement of cellular concrete design and usage worldwide.
What are the disadvantages of cellular concrete, compared to typical concrete? In the lower density ranges cellular concrete does not develop the compressive strength of plain concrete. While this may be a disadvantage in plain concrete applications, it is an advantage in a cellular concrete application. It should be considered that cellular concrete and plain 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. To produce cellular concrete utilizing the pre-formed foam method you must have access to a foam generating device.
What construction challenges are appropriate to meet with cellular concrete? Geotechnical Applications Tunnel Backfill and Annular Fill • Replacement for Unstable Soils • Load Reducing Engineered Fill over Underground Structures • Fill for Abandoned tanks, mines and pipelines • Bridge Approach Fills • Land slip repair fills • Shock Energy Absorption Construction and Insulation Poured Insulated Roof and Floor Decks • Acoustic Floor Underlayments • Slab-on–Grade Construction Sub Grade Replacements or Repair • Underground Pipe Insulation • Precast Slabs and Panels • Housing Systems NOTE: Midwest Cellular Concrete has detailed information available for several of the applications listed.
Is there a difference in the preformed foam for Geotechnical applications and roof, floor or other layment applications? Yes! Special formulations of foam concentrate are blended depending on the application. There are also various blends and mix designs within each category of concentrate. Midwest Cellular Concrete Inc. can advise you on product selection. As an example, a sloped roof deck might require a product with a relatively slow flow rate and low density to maintain a slope with low unit weight. Conversely, a Geotechnical bulk fill application might require a very fluid and fast flowing product with a heavier density to fill all the small fissures in the project with a higher weight concrete.
How do I specify cellular concrete? Midwest Cellular Concrete Inc. can furnish you with written or digital specifications that are appropriate to your application. Basic specifications can also be obtained via e-mail from hrkalco@netzero.com or online through our Cellular Tech Sheets link.
Where do I purchase cellular concrete? Cellular concrete is purchased installed from factory trained specialty contractors who have factory training in the field of cellular concrete installation. Midwest Cellular Concrete Inc. uses the most productive, highest technology equipment. This equipment, in conjunction with quality materials and thousands of cubic yards placed, make Midwest Cellular Concrete Inc. a production leader in the industry.
How is cellular concrete placed? The pre-formed foam is added to the cement slurry and mixed in the concrete mixer or in a continuous process. From that point, cellular concrete is placed in any way that a fluid mix can be transported. Pumping is the most common method of placement. Tailgate ready mix truck delivery, bucket cranes, wheelbarrows, hand carried buckets and any other acceptable method of delivering a fluid mix works well.
Do the bubbles in cellular concrete collapse, reducing its volume? Not with well engineered pre-formed foam products. 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. The proposed pre-formed foam for an application should be tested for stability or certified for stability prior to actual project placement.
Can cellular concrete be under mixed? 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.
Can cellular concrete be over mixed? Mixing until there is a reduction of volume of product is not recommended. Air cell stability is the mark of a superior foam concentrate and foam generator combination. With typical mixing procedures, cellular concrete formulated with quality pre-formed foam is very stable even with modestly extended mixing times.
Is cellular concrete chemically compatible with common Foaming Agents? Cellular concrete is compatible with common concrete construction Foaming Agents; however, most common Foaming Agents are added to plain concrete to affect 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 Foaming Agents and strength enhancing Foaming Agents work well.
What Ad Agents are common to cellular concrete? Fiber reinforcement - Heat-of-hydration reducers (iced water or chemicals) - Compressive strength enhancers - Coloring pigments or color enhancing Foaming Agents
How far can cellular concrete be pumped? Documentation of cellular concrete being pumped 500 ft. vertically and 10,000 horizontally is common and available via the ASCE bookstore. Is segregation a problem? Unlike plain 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.
How do you finish cellular concrete? Most cellular concrete is left to self-seek a level and not finished in the traditional sense. Most cellular concrete is covered by another material. A layment type smoothing tool can be used simply to break the surface air cells and create a more uniform and polished look to the surface when a more uniform surface is desired.
How much does cellular concrete cost? Cost of cellular concrete varies by geographical area and by application requirements. Midwest Cellular Concrete Inc. will be glad to assist you with budget numbers and binding quotations for your project. It is important that you make sure you are seeking pricing from a qualified cellular concrete contractor or their suppliers to understand the pricing for a specific project.
How does cellular concrete compare in price to plain concrete? A typical cellular concrete project can be much less expensive cubic yard to cubic yard in place when compared to plain concrete due to labor savings, less cost of forming and the price savings when comparing pre-formed foam to aggregate pricing.
How do I test cellular concrete to determine if it is performing to specs? Documentation of a comprehensive set of test procedures for cellular concrete are beyond the scope of this document; however, Midwest Cellular Concrete Inc. will be happy to assist you in the actual testing or furnishing descriptions of common tests. Properties commonly tested are: density - compressive strength.
Is cellular concrete the same as CLSM “flowable” fill? No! Flowable fill is typically a cement & fly ash slurry mix. 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 when compared to flowable fill. Often flowable fill reaches compressive strengths that make future excavation and removal of the material problematic. Low density cellular concrete is very easy to remove with only hand tools and still maintains integrity above that of typical soil fills. 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.
Is cellular concrete the same as lightweight concrete? 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 60 lb. / cu. ft. The Hrkal Companies through Lightweight Distributing Company specializes in the distribution of the highest quality lightweight aggregate for lightweight concrete applications. The Hrkal Companies has specialized in lightweight concrete for over 30 years.
Is cellular concrete suitable for long-term use as a marine float device? Cellular concrete will float, and in many cases float indefinitely. Because of its basic nature, cellular concrete used for marine flotation should be encased and used for the fill of a float. For example, a superior marine float could be made with sealed 55 gallon drums full of low density cellular concrete.
Is cellular concrete a suitable material for a concrete canoe? Once again, similar in scope to the question regarding marine float applications, cellular concrete could be used for the fill in a concrete canoe but should probably be encased in a waterproof membrane.
Is it appropriate to reinforce cellular concrete with synthetic fibers? 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.
Is it appropriate to reinforce cellular concrete with steel fibers? 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 particular reason not to reinforce a cellular concrete design with steel design.
